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GASTROINTESTINAL SYSTEM - LONG ANSWER QUESTIONS (10 Marks Each)

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Q1. Define peptic ulcer. Classify antiulcer drugs. Discuss the mechanism of action, therapeutic uses and adverse effects of proton pump inhibitors.

Definition of Peptic Ulcer

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Classification of Antiulcer Drugs

• A. Proton Pump Inhibitors (PPIs): Omeprazole, Lansoprazole, Pantoprazole, Rabeprazole, Esomeprazole
• B. H2-Receptor Antagonists: Cimetidine, Ranitidine, Famotidine, Nizatidine
• C. Anticholinergic drugs: Pirenzepine (M1-selective)
• D. Prostaglandin analogues: Misoprostol

• Systemic: Sodium bicarbonate
• Non-systemic: Magnesium hydroxide, Aluminium hydroxide, Calcium carbonate, Magnesium trisilicate

• Sucralfate
• Colloidal bismuth subcitrate (CBS)
• Carbenoxolone

• Triple therapy, Quadruple therapy (see Q5)

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Proton Pump Inhibitors (PPIs)

Mechanism of Action

• PPIs are prodrugs. They are weak bases (pKa ~4) that concentrate in the acidic canaliculi of parietal cells.
• In the acidic environment, they are protonated and converted to active sulphenamide derivatives.
• This active form covalently (irreversibly) binds to the cysteine residues of the H+/K+-ATPase enzyme (the proton pump) on the luminal surface of parietal cells.
• This blocks the final common pathway of acid secretion, suppressing both basal and stimulated acid secretion (by histamine, gastrin, and acetylcholine) by up to 95-98%.
• Acid secretion resumes only when new proton pumps are synthesized (~18-24 hours).
• PPIs are most effective when taken 30-60 minutes before meals (when proton pumps are activated).

Therapeutic Uses

1. Peptic ulcer disease - duodenal and gastric ulcers (heals faster than H2 blockers)
2. H. pylori eradication - as part of triple or quadruple therapy
3. GERD - drug of choice; heals erosive esophagitis
4. Zollinger-Ellison syndrome - drug of choice (large doses required)
5. Prevention of NSAID-induced ulcers - given prophylactically with NSAIDs
6. Stress ulcer prophylaxis in ICU patients
7. Upper GI bleeding - IV PPIs reduce re-bleeding risk

Adverse Effects

1. Common (short-term): Headache, nausea, diarrhea, abdominal pain, flatulence
2. Hypomagnesemia - with prolonged use (>1 year); can cause tetany, arrhythmias
3. Hyponatremia, hypokalemia - electrolyte disturbances
4. Vitamin B12 deficiency - reduced intrinsic factor activity and absorption
5. Iron deficiency - reduced absorption of non-heme iron
6. Increased risk of infections:
   • Clostridium difficile colitis
   • Community-acquired pneumonia
   • Enteric infections (due to loss of acid barrier)
7. Osteoporosis and fractures - long-term use reduces calcium absorption
8. Rebound acid hypersecretion on abrupt discontinuation
9. Drug interactions: Clopidogrel (reduced antiplatelet effect via CYP2C19 inhibition by omeprazole), reduced absorption of ketoconazole, atazanavir, iron

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Q2. Define peptic ulcer. Classify antiulcer drugs. Discuss the mechanism of action, therapeutic uses and adverse effects of H2-receptor antagonists.

H2-Receptor Antagonists

• Potency ratio: Famotidine > Nizatidine > Ranitidine > Cimetidine (1:1:2:40)

Mechanism of Action

• Competitively block histamine H2 receptors on the basolateral membrane of parietal cells.
• Histamine, released from ECL cells under gastrin stimulation, activates adenylyl cyclase via H2 receptors, raising cAMP, which activates protein kinase A to phosphorylate and activate the H+/K+-ATPase pump.
• H2 blockers competitively prevent histamine binding, reducing cAMP, thereby reducing acid secretion.
• They suppress basal (especially nocturnal) acid secretion by ~70% and meal-stimulated acid by ~60%.
• They do NOT suppress gastrin or acetylcholine stimulation as effectively as PPIs.

Therapeutic Uses

1. Peptic ulcer disease - duodenal ulcer (heals 85-90% in 6 weeks), gastric ulcer (12 weeks)
2. GERD - mild to moderate; especially for nocturnal symptoms
3. Zollinger-Ellison syndrome (high doses needed; PPIs preferred)
4. Prevention of stress ulcers in critically ill patients
5. NSAID-associated ulcers (prevention and treatment)
6. Prophylaxis of aspiration pneumonitis before anesthesia (raises gastric pH)
7. Urticaria and allergic conditions (limited, as H1 blockers are preferred)

Adverse Effects

1. CNS effects (Cimetidine mainly): Headache, dizziness, confusion, mental changes (especially in elderly); crosses BBB
2. Antiandrogenic effects (Cimetidine): Gynecomastia, impotence, reduced sperm count - due to blockade of androgen receptors
3. Drug interactions (Cimetidine): Inhibits CYP450 enzymes - reduces metabolism of warfarin, phenytoin, theophylline, diazepam, propranolol leading to toxicity
4. Thrombocytopenia - rare
5. Elevated liver enzymes, hepatitis - rare with cimetidine
6. Bradycardia, hypotension - with rapid IV injection
7. Tolerance - develops on prolonged use (up-regulation of H2 receptors)
8. Rebound acid hypersecretion on withdrawal
9. Ranitidine: less CNS and antiandrogenic effects; fewer drug interactions

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Q3. Classify antacids. Discuss the pharmacological actions, therapeutic uses and adverse effects of non-systemic antacids.

Classification of Antacids

• Sodium bicarbonate
• Sodium citrate

• Aluminium hydroxide [Al(OH)3]
• Magnesium hydroxide [Mg(OH)2] - Milk of Magnesia
• Magnesium trisilicate
• Calcium carbonate
• Combinations: Magaldrate (aluminum magnesium hydroxide sulfate), Gelusil, Digene

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Non-Systemic Antacids

Pharmacological Actions

1. Acid neutralization: React with HCl in the stomach to raise gastric pH. Since pepsin is inactive above pH 4, raising pH above 4 inactivates pepsin and provides mucosal protection.
   • Al(OH)3 + 3HCl → AlCl3 + 3H2O
   • Mg(OH)2 + 2HCl → MgCl2 + 2H2O
2. Do not produce systemic alkalosis - because their products (AlCl3, MgCl2) are poorly absorbed or form insoluble salts in the intestine.
3. Aluminium hydroxide also has adsorbent, astringent and mild cytoprotective properties; reduces pepsin activity.
4. Magnesium hydroxide has cathartic/laxative action - osmotic effect.
5. Calcium carbonate releases CO2 which causes belching; also has antacid + constipating effects.
6. Magnesium trisilicate forms silica gel which may have cytoprotective effects.

Therapeutic Uses

1. Peptic ulcer disease (adjuvant therapy for symptomatic relief)
2. GERD (symptomatic relief of heartburn)
3. Dyspepsia and hyperacidity
4. Gastritis
5. Aluminium hydroxide is used in chronic renal failure to bind dietary phosphate and reduce hyperphosphataemia
6. Calcium carbonate - also used as calcium supplement in osteoporosis
7. Antacid combinations (Al + Mg) are preferred to balance effects and reduce adverse effects

Adverse Effects

• Constipation (most important)
• Hypophosphatemia with prolonged use (binds dietary phosphates) - leads to osteomalacia, muscle weakness
• Aluminium toxicity in renal failure - encephalopathy, osteomalacia (dialysis dementia)
• Reduced absorption of tetracyclines, fluoroquinolones, iron, digoxin (chelation)

• Diarrhea, loose stools (laxative effect)
• Hypermagnesemia in renal failure - causes neuromuscular depression, hypotension, respiratory failure
• Drug interactions (reduces absorption of tetracyclines, fluoroquinolones)

• Constipation
• Belching (CO2 release)
• Milk-alkali syndrome (hypercalcemia, alkalosis, renal failure) with large doses
• Rebound acid secretion (due to gastrin release stimulated by calcium)

• Combined Al+Mg preparations balance constipation vs. diarrhea and are well-tolerated

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Q4. Classify antiulcer drugs. Discuss ulcer protective agents with suitable examples.

Ulcer Protective Agents (Cytoprotective Agents)

1. Sucralfate

• In the acidic environment of the stomach (pH <4), sucralfate polymerizes into a sticky, viscous gel.
• This gel selectively adheres to the ulcer crater (binds to positively charged proteins in the ulcer base - albumin, fibrinogen) and forms a protective barrier for 4-6 hours.
• Prevents further acid and pepsin attack on the ulcer.
• Stimulates prostaglandin synthesis, mucus secretion, and bicarbonate secretion - enhancing mucosal defense.
• Adsorbs and inactivates pepsin and bile acids.
• Promotes growth factor (EGF, bFGF) binding to the ulcer site, enhancing healing.

• Duodenal ulcer (as effective as H2 blockers)
• Gastric ulcer
• Prevention of stress ulcers in ICU
• Prophylaxis of NSAID-induced ulcers
• Reflux esophagitis (limited)

• Constipation (most common - 2-3%)
• Dry mouth
• May reduce absorption of fluoroquinolones, tetracycline, digoxin, phenytoin, warfarin (adsorption)
• Aluminum accumulation in renal failure
• Must be taken on empty stomach; NOT to be combined with antacids (requires acid for activation)

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2. Colloidal Bismuth Subcitrate (CBS) / Tripotassium Dicitratobismuthate (De-Nol)

• In acid environment, precipitates as bismuth oxychloride and bismuth citrate - forms a protective coat over the ulcer.
• Binds to glycoprotein in the mucus, forming a protective barrier.
• Stimulates prostaglandin and bicarbonate secretion.
• Bactericidal against H. pylori - directly toxic to H. pylori (inhibits its urease, phospholipase, proteolytic enzymes); used as part of H. pylori eradication therapy.
• Adsorbs pepsin and bile acids.

• Duodenal and gastric ulcers
• H. pylori eradication (quadruple therapy: CBS + PPI + amoxicillin + clarithromycin/metronidazole)

• Black discolouration of stools and tongue (harmless - bismuth sulphide)
• Nausea, vomiting, headache
• Encephalopathy (neurotoxicity) with excessive long-term use (bismuth accumulation)
• Avoid in renal failure

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3. Carbenoxolone

• Semi-synthetic derivative of glycyrrhizinic acid (liquorice).
• Increases mucus secretion and improves its quality.
• Prolongs the lifespan of gastric mucosal cells.
• Stimulates prostaglandin synthesis.

• Pseudohyperaldosteronism: sodium and water retention, hypokalemia, hypertension, edema (major limiting factor; interacts with aldosterone receptors)
• Now largely replaced by PPIs.

4. Misoprostol (Prostaglandin analogue - E1 analogue)

• Stimulates mucus and bicarbonate secretion, maintains mucosal blood flow.
• Reduces acid secretion (via Gi-coupled PGE2 receptors on parietal cells).
• Main use: Prevention of NSAID-induced ulcers (drug of choice).
• Adverse effects: Diarrhea, abdominal cramps, uterine contraction (contraindicated in pregnancy).

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Q5. Describe the role of H. pylori in peptic ulcer disease. Discuss the pharmacological management of H. pylori infection.

Role of H. pylori in Peptic Ulcer Disease

• H. pylori is a gram-negative spiral bacterium that colonizes the gastric antrum.
• Found in ~95% of duodenal ulcers and ~70-80% of gastric ulcers.
• Mechanisms of damage:
  1. Produces urease - converts urea to ammonia and CO2; ammonia is cytotoxic and neutralizes local acid, protecting the organism.
  2. Produces proteases, phospholipases, and vacuolating cytotoxin (VacA) - damage mucus layer and epithelial cells.
  3. CagA protein - injected into epithelial cells, causes inflammatory response and oncogenic changes.
  4. Triggers chronic gastritis, increasing gastrin secretion, raising acid output.
  5. Reduces somatostatin-secreting D cells, further reducing inhibition of gastrin and increasing acid.
  6. Stimulates mucosal inflammation (neutrophil, macrophage infiltration) - cytokines (IL-1, IL-6, TNF-alpha) damage mucosa.
• Eradication of H. pylori leads to ulcer healing and dramatically reduces recurrence rates.

Pharmacological Management of H. pylori

Diagnosis first: Urea breath test, stool antigen test, endoscopy biopsy (CLO test, histology, culture)

Treatment Regimens:

• PPI (Omeprazole 20 mg BD) + Clarithromycin (500 mg BD) + Amoxicillin (1 g BD) OR
• PPI (Omeprazole 20 mg BD) + Clarithromycin (500 mg BD) + Metronidazole (400 mg BD) - if penicillin allergy

• PPI + Colloidal Bismuth Subcitrate (CBS) + Tetracycline (500 mg QID) + Metronidazole (400 mg TID)

• PPI + Clarithromycin + Amoxicillin + Metronidazole

• Days 1-5: PPI + Amoxicillin
• Days 6-10: PPI + Clarithromycin + Metronidazole/Tinidazole

• PPI + Amoxicillin + Levofloxacin OR Rifabutin

• PPI: Raises gastric pH, reducing acid environment hostile to antibiotics; increases antibiotic effectiveness
• Clarithromycin: Inhibits protein synthesis (50S ribosome); best intracellular penetration
• Amoxicillin: Inhibits cell wall synthesis; bactericidal; low resistance
• Metronidazole: Disrupts DNA; active against anaerobic/microaerophilic organisms
• Bismuth: Direct bactericidal action on H. pylori

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Q6. Define GERD. Discuss its pharmacological management.

Definition of GERD

Pathophysiology

• Transient lower esophageal sphincter relaxations (TLESRs) - most important mechanism
• Reduced LES tone
• Delayed gastric emptying
• Impaired esophageal clearance
• Hiatus hernia

Pharmacological Management

Step 1: Lifestyle Modifications

• Avoid trigger foods (coffee, chocolate, fatty foods, alcohol, citrus), elevate head of bed, reduce weight, avoid meals 3 hours before lying down.

Step 2: Antacids

• For immediate, short-term symptomatic relief of heartburn.
• Aluminium hydroxide + Magnesium hydroxide combinations.
• Alginate antacids (Gaviscon) - form a raft that floats on stomach contents, reducing reflux.

Step 3: H2-Receptor Antagonists

• Reduce acid secretion; effective for mild-moderate GERD without erosive esophagitis.
• Ranitidine 150 mg BD or Famotidine 20 mg BD.
• Particularly useful for nocturnal symptoms.

Step 4: Proton Pump Inhibitors (DRUGS OF CHOICE)

• Omeprazole 20-40 mg OD (before breakfast), Pantoprazole, Lansoprazole, Rabeprazole.
• Suppress acid secretion maximally; heal erosive esophagitis in 4-8 weeks.
• Superior to H2 blockers in healing and symptom relief.
• Long-term maintenance therapy required for most GERD patients.
• Esomeprazole (S-isomer of omeprazole) has slightly better bioavailability.

Step 5: Prokinetic Agents

• Metoclopramide, Domperidone, Itopride.
• Increase LES tone, enhance gastric emptying, improve esophageal motility.
• Adjuvant therapy with PPIs in GERD.
• Metoclopramide: useful but causes CNS side effects (extrapyramidal reactions).

Step 6: Surgery

• Laparoscopic Nissen fundoplication - for patients who fail medical therapy or want to discontinue long-term medications.

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Q7. Define GERD. Discuss the role of PPIs, H2-receptor antagonists and prokinetic agents in its management.

1. Increase LES tone - prevent reflux
2. Accelerate gastric emptying - reduces gastric distension, decreases pressure gradient
3. Improve esophageal peristalsis - enhances clearance of refluxed material

• Metoclopramide: D2 blocker, increases LES tone, prokinetic. Limited use in GERD due to CNS side effects.
• Domperidone: D2 blocker (peripheral), fewer CNS effects, increases LES pressure, promotes gastric emptying.
• Cisapride: 5HT4 agonist (withdrawn due to cardiac arrhythmias - QTc prolongation).
• Mosapride: 5HT4 agonist, used in India for GERD.
• Itopride: D2 blocker + acetylcholinesterase inhibitor - increases gastric motility.

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Q8. Classify prokinetic agents. Discuss the pharmacological actions, therapeutic uses and adverse effects of metoclopramide.

Classification of Prokinetic Agents

1. Dopamine D2 receptor antagonists:
   • Metoclopramide
   • Domperidone
   • Itopride (also has AChE inhibitory activity)
2. 5-HT4 receptor agonists:
   • Cisapride (withdrawn)
   • Mosapride
   • Tegaserod
3. Motilin receptor agonists:
   • Erythromycin (macrolide antibiotic)
4. Combination:
   • Itopride (D2 blocker + AChE inhibitor)

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Metoclopramide

Mechanism of Action / Pharmacological Actions

• Blocks D2 receptors in the GI tract - dopamine normally inhibits ACh release and reduces motility; blocking D2 receptors increases ACh release.
• This increases:
  • Lower esophageal sphincter (LES) tone
  • Gastric peristalsis and rate of gastric emptying
  • Small intestinal transit
  • Coordinates gastroduodenal peristalsis
• Does NOT affect colonic motility significantly.

• Blocks D2 receptors in the chemoreceptor trigger zone (CTZ) of the area postrema - the primary antiemetic mechanism.
• Blocks 5-HT3 receptors at higher doses - contributes to antiemetic effect (especially in chemotherapy-induced nausea).

• Crosses the blood-brain barrier - causes CNS effects (see adverse effects).
• Prolactin release - blocks D2 receptors in anterior pituitary (tuberoinfundibular pathway).

Therapeutic Uses

1. Antiemetic - nausea and vomiting due to:
   • Post-operative nausea
   • Drug-induced nausea (opioids, cytotoxics at higher doses)
   • Radiation sickness
   • Migraine-associated nausea
2. Gastroparesis - (delayed gastric emptying in diabetics, post-surgical)
3. GERD - adjunct to antacids/PPIs
4. Facilitation of small bowel intubation - accelerates passage of tube through pylorus
5. Radiological examination - accelerates contrast transit
6. Hyperemesis gravidarum (used cautiously)
7. Prevention of aspiration before anesthesia (with antacids)

Adverse Effects

1. Extrapyramidal reactions (EPR) - most important:
   • Acute dystonia (torticollis, oculogyric crisis, trismus) - especially in young patients
   • Akathisia (restlessness)
   • Parkinsonism (tremor, rigidity, bradykinesia) with prolonged use
   • Tardive dyskinesia - with long-term use (potentially irreversible)
   • Treated with anticholinergics (benztropine) or antihistamines (diphenhydramine)
2. Hyperprolactinemia - galactorrhoea, amenorrhoea, gynecomastia, impotence
3. CNS effects: Drowsiness, sedation, anxiety, depression
4. Diarrhea (due to increased GI motility)
5. Cardiovascular: Rare hypertension, QT prolongation at high doses
6. Contraindicated in: Parkinson's disease, pheochromocytoma (hypertensive crisis), GI obstruction/perforation, epilepsy

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Q9. Classify prokinetic agents. Discuss the pharmacological actions, therapeutic uses and adverse effects of domperidone.

Domperidone

Mechanism of Action / Pharmacological Actions

• Blocks D2 receptors in the GI tract - same peripheral mechanism as metoclopramide.
• Increases LES tone and esophageal peristalsis.
• Enhances gastric emptying and gastric peristalsis.
• Improves gastroduodenal coordination.

• The CTZ (area postrema) is outside the BBB - domperidone reaches CTZ and blocks D2 receptors here.
• Acts as antiemetic via CTZ blockade WITHOUT significant CNS side effects.

• Blocks tuberoinfundibular D2 receptors (pituitary) - these lie outside BBB, so domperidone can access them.
• Increases prolactin secretion.

Key Advantage Over Metoclopramide

• Does NOT cross the BBB significantly, so NO extrapyramidal side effects (no dystonia, no parkinsonism).
• Safer for long-term use and in elderly patients.
• Cannot block D2 receptors in the basal ganglia.

Therapeutic Uses

1. Nausea and vomiting - drug-induced (levodopa, ergotamine, bromocriptine), post-operative
2. Gastroparesis and delayed gastric emptying
3. GERD - increases LES tone and gastric emptying
4. Functional dyspepsia (bloating, nausea, fullness)
5. Used to stimulate lactation (galactogogue) in nursing mothers - increases prolactin
6. Anti-Parkinson drug-induced nausea (domperidone preferred over metoclopramide because it doesn't worsen Parkinson's symptoms)

Adverse Effects

1. Hyperprolactinemia - galactorrhoea, amenorrhoea, gynecomastia (since pituitary is outside BBB)
2. Cardiac effects: QT interval prolongation, risk of ventricular arrhythmias (torsades de pointes) - especially at high doses; FDA/EMA warnings issued
3. Dry mouth, headache - mild
4. GI disturbances - diarrhea, abdominal cramps (rare)
5. No significant extrapyramidal effects (major advantage)
6. Contraindicated in patients with QT prolongation, hepatic failure, or concomitant use with CYP3A4 inhibitors (raise domperidone levels).

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Q10. Classify antiemetic drugs. Discuss the mechanism of action, therapeutic uses and adverse effects of ondansetron.

Classification of Antiemetic Drugs

• Phenothiazines: Prochlorperazine, Chlorpromazine
• Butyrophenones: Haloperidol, Droperidol
• Metoclopramide, Domperidone

• Ondansetron, Granisetron, Tropisetron, Palonosetron, Ramosetron

• Promethazine, Cyclizine, Meclizine, Dimenhydrinate

• Hyoscine (Scopolamine) - motion sickness

• Aprepitant, Fosaprepitant, Netupitant

• Dronabinol (THC), Nabilone

• Dexamethasone, Methylprednisolone

• Lorazepam (for anticipatory nausea)

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Ondansetron

Mechanism of Action

• Serotonin (5-HT) released from enterochromaffin cells in the GI mucosa (especially during cytotoxic drug/radiation exposure) stimulates 5-HT3 receptors on vagal afferents, which transmit signals to the vomiting center and CTZ.
• Ondansetron selectively and competitively blocks 5-HT3 receptors both peripherally (GI tract) and centrally (CTZ in area postrema, nucleus tractus solitarius).
• Blocks the vagal afferent signals triggered by chemotherapy/radiation.
• Does NOT block D2, H1, M, or alpha-adrenergic receptors - hence no extrapyramidal effects or sedation.

Therapeutic Uses

1. Chemotherapy-induced nausea and vomiting (CINV) - drug of choice; highly effective for highly emetogenic chemotherapy (e.g., cisplatin)
2. Radiation-induced nausea and vomiting - especially total body irradiation
3. Post-operative nausea and vomiting (PONV) - given prophylactically before surgery
4. Nausea due to opioids
5. Hyperemesis gravidarum (second line)

Adverse Effects

1. Headache (most common ~10-20%)
2. Constipation - due to reduced GI serotonin activity
3. QT interval prolongation - risk of ventricular arrhythmias; use caution with other QT-prolonging drugs
4. Diarrhea (less common)
5. Elevated liver transaminases - transient
6. Flushing, dizziness, fatigue
7. Serotonin syndrome - rare, especially in combination with other serotonergic drugs
8. No extrapyramidal effects, no sedation (major advantages over metoclopramide)

Pharmacokinetics

• Well absorbed orally; available as tablets, ODT (orally disintegrating), IV formulations.
• Metabolized by CYP3A4, CYP1A2.
• Half-life: ~3-4 hours; given 8-hourly.
• Palonosetron: longer half-life (~40 hours); preferred for delayed CINV.

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Q11. Classify antiemetic drugs. Discuss the pharmacological actions, therapeutic uses and adverse effects of metoclopramide.

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Q12. Classify antiemetic drugs. Discuss drugs used in chemotherapy-induced nausea and vomiting.

Drugs Used in Chemotherapy-Induced Nausea and Vomiting (CINV)

• Acute phase: Within 24 hours of chemotherapy (mediated by serotonin)
• Delayed phase: 24-120 hours after chemotherapy (mediated by substance P/NK1)
• Anticipatory CINV: Before chemotherapy (conditioned response, mediated by CNS)

1. 5-HT3 Antagonists (First-line for acute CINV)

• Ondansetron 8 mg IV/oral - drug of choice
• Granisetron, Tropisetron, Palonosetron (preferred for delayed phase due to long half-life)
• Mechanism: Block 5-HT3 receptors on vagal afferents and CTZ.

2. NK1 (Substance P) Antagonists (For delayed CINV and with highly emetogenic regimens)

• Aprepitant (oral), Fosaprepitant (IV prodrug)
• Block NK1 receptors in the brain and GI tract.
• Substance P is the main mediator of delayed CINV.
• Combined with ondansetron + dexamethasone for highly emetogenic chemotherapy (e.g., cisplatin, cyclophosphamide).

3. Corticosteroids (Adjuvant - mechanism unclear)

• Dexamethasone 8-20 mg IV before chemotherapy.
• Mechanism may involve reduction of prostaglandins, 5-HT release, or direct CNS effect.
• Enhances efficacy of ondansetron by 30-40%.
• Used in both acute and delayed CINV.

4. D2 Antagonists (For breakthrough/rescue)

• Metoclopramide (high doses - 2-3 mg/kg IV) - blocks D2 and 5-HT3 at high doses.
• Prochlorperazine - phenothiazine, for breakthrough nausea.
• Haloperidol - low-dose.

5. Cannabinoids

• Dronabinol (delta-9-THC), Nabilone - CB1 receptor agonists.
• Used for refractory CINV not responding to above agents.
• Adverse effects: dysphoria, sedation, hallucinations.

6. Benzodiazepines

• Lorazepam - for anticipatory CINV; anxiolytic + amnestic properties.

Standard Triple Antiemetic Regimen (Highly Emetogenic Chemotherapy):

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Q13. Classify antiemetic drugs and discuss their therapeutic applications in different clinical conditions.

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Q14. Classify laxatives. Discuss bulk-forming laxatives and stool softeners.

Classification of Laxatives

• Dietary fibre: Bran, psyllium (ispaghula/Isabgol)
• Methylcellulose
• Sterculia

• Saline: Magnesium sulphate (Epsom salt), Magnesium hydroxide, Sodium sulphate
• Osmotic: Lactulose, Polyethylene glycol (PEG), Sorbitol, Mannitol

• Anthraquinone group: Senna, Cascara, Aloe
• Diphenylmethane group: Bisacodyl, Phenolphthalein (withdrawn)
• Castor oil (ricinoleic acid)

• Docusate sodium (DOSS)
• Liquid paraffin (mineral oil)

• Liquid paraffin

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Bulk-Forming Laxatives

Mechanism of Action

• Hydrophilic polysaccharides and cellulose derivatives that are not digested or absorbed in the GI tract.
• Absorb water and swell, increasing fecal bulk and mass.
• The increased bulk distends the colon and stimulates peristalsis via stretch receptors.
• Also softens the stool as they retain water.
• Onset: 12-72 hours (slow, physiological laxation).

Therapeutic Uses

1. Constipation - safest laxative; first-line for chronic constipation
2. Irritable bowel syndrome (IBS) - both constipation and diarrhea variants
3. Diverticular disease - prevents diverticulitis
4. Hemorrhoids and anal fissures - soft stools reduce straining
5. Post-anorectal surgery - avoid straining
6. Hyperlipoproteinemia - reduce cholesterol absorption (minor effect)
7. Diabetes - delay glucose absorption

Adverse Effects

1. Flatulence, bloating, abdominal distension
2. Esophageal and intestinal obstruction if taken without adequate water
3. Bezoar formation (rare)
4. Reduced absorption of drugs (warfarin, digoxin, salicylates) if taken together
5. Must be taken with adequate water (at least 200-300 mL)

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Stool Softeners (Emollient Laxatives)

1. Docusate Sodium (DOSS - Dioctyl Sodium Sulphosuccinate)

• Anionic surfactant (surface active agent) - reduces surface tension of the fecal mass.
• Allows water and lipids to penetrate the fecal mass.
• Softens the stool without increasing bulk or stimulating peristalsis.
• Onset: 1-3 days.

• Constipation in elderly, cardiac patients (avoid straining/Valsalva)
• Post-MI, post-hernia repair, post-anorectal surgery
• Hemorrhoids, anal fissure
• Used to clear ear wax (docusate ear drops)

• Generally well-tolerated
• Diarrhea with excessive use
• Enhances absorption of other drugs (mineral oil - absorption of fat-soluble vitamins)
• Hepatotoxicity with prolonged use (rare)

2. Liquid Paraffin (Mineral Oil)

• Lubricates and softens stool; coats fecal mass preventing water absorption.

• Lipid pneumonia - aspiration, especially in elderly/debilitated (major risk)
• Malabsorption of fat-soluble vitamins (A, D, E, K)
• Anal seepage causing pruritus ani and perianal irritation
• Long-term use: lipogranuloma of mesenteric lymph nodes
• Not recommended for routine use.

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Q15. Classify laxatives. Discuss osmotic purgatives with reference to their pharmacological actions, therapeutic uses and adverse effects.

Osmotic Purgatives

• Saline purgatives: Magnesium sulphate (Epsom salt), Magnesium hydroxide (milk of magnesia), Sodium sulphate (Glauber's salt)
• Sugar alcohols: Lactulose, Sorbitol, Mannitol
• Polyethylene glycol (PEG) - macrogol

Mechanism of Action

• Poorly absorbed from the gut.
• Retain water in the intestinal lumen by osmotic pressure.
• This increases intraluminal fluid, distends the bowel and stimulates peristalsis.
• Magnesium salts also release cholecystokinin (CCK), which stimulates intestinal motility and secretion.
• Onset: 2-6 hours (rapid action; used when quick bowel evacuation needed).

• Synthetic disaccharide (fructose + galactose) not hydrolyzed by human intestinal disaccharidases.
• Reaches the colon unchanged where colonic bacteria ferment it to short-chain fatty acids (lactic acid, acetic acid, formic acid) and gases.
• The acids lower colonic pH and increase osmotic pressure, drawing water into the colon and softening stools.
• In hepatic encephalopathy: The acidic environment converts ammonia (NH3) to ammonium (NH4+), which is non-absorbable and is trapped and excreted in the feces. This reduces blood ammonia levels.
• Onset: 24-72 hours (slow).

• Large polymer; not absorbed, not metabolized by colonic bacteria.
• Retains water osmotically throughout the GI tract.
• Used as bowel preparation before colonoscopy/surgery.
• PEG 3350 (Movicol) - used for chronic constipation; well tolerated.

Therapeutic Uses

Adverse Effects

• Excessive diarrhea, dehydration, electrolyte imbalance (Na+, K+ loss)
• Hypermagnesemia in renal failure (magnesium salts) - neuromuscular depression
• Reflex sodium retention in heart failure/cirrhosis (sodium salts)
• Not for routine use or long-term constipation management

• Flatulence, bloating, abdominal cramps (due to gas production by bacterial fermentation)
• Diarrhea with excessive doses
• Nausea
• Hypernatremia with prolonged use (fluid loss exceeds Na+ loss)
• Diabetes: contains small amounts of absorbed sugars

• Generally well-tolerated
• Bloating, nausea
• Large volumes required for bowel prep

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Q16. Classify laxatives. Discuss stimulant purgatives with suitable examples.

Stimulant (Irritant) Purgatives

1. Anthraquinone glycosides: Senna (sennosides), Cascara sagrada, Aloe
2. Diphenylmethane derivatives: Bisacodyl, Phenolphthalein (withdrawn)
3. Castor oil (ricinoleic acid)
4. Oxyphenisatin (withdrawn)

Mechanism of Action

• These drugs stimulate the enteric nervous system and increase intestinal motility by:
  1. Direct irritation of the intestinal mucosa, stimulating submucosal and myenteric plexuses.
  2. Inhibiting electrolyte (Na+/K+ ATPase) and water absorption, promoting net secretion into the bowel lumen.
  3. Increasing colonic motility and reducing transit time.

• Converted in the colon by bacterial hydrolysis to active anthraquinones (e.g., rhein anthrone).
• Stimulate colonic epithelium and ENS; act on large intestine.
• Onset: 6-12 hours.

• Converted by intestinal esterases to active form (des-acetyl bisacodyl) in the intestine.
• Stimulates the sensory nerve endings and ENS in the colon wall.
• Acts on both small and large intestine.
• Can be given orally (10 mg, onset 6-10 hours) or rectally as suppository (onset 1 hour).

• Hydrolyzed by lipase in the small intestine to ricinoleic acid, which acts as a stimulant laxative.
• Acts on small intestine; onset 2-6 hours.
• Produces watery diarrhea.
• Used to prepare bowel before surgery; safe in pregnancy for labor induction (stimulates uterine contractions via prostaglandin release).

Therapeutic Uses

1. Constipation (short-term use; not for chronic use)
2. Bowel preparation before colonoscopy, radiological procedures, surgery
3. Castor oil - bowel prep, retained oil enema
4. Senna - most commonly used OTC stimulant laxative

Adverse Effects

1. Abdominal cramps, colic (most common)
2. Diarrhea, electrolyte imbalance - hypokalemia, hyponatremia
3. Cathartic colon (with long-term abuse) - atonic non-functional colon (loss of Auerbach's plexus); produces dependence
4. Melanosis coli (with anthraquinones) - dark pigmentation of colonic mucosa (due to lipofuscin deposits in macrophages); benign but marker of laxative abuse
5. Hypokalemia - dangerous with cardiac glycosides, may precipitate toxicity
6. Drug dependence - "laxative abuse syndrome"
7. Phenolphthalein: withdrawn due to carcinogenicity
8. Castor oil: uterine contractions (avoid in pregnancy except for labor)

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Q17. Discuss the pharmacological management of constipation.

Definition

Non-Pharmacological Management

• Increase dietary fiber (25-30 g/day)
• Increase fluid intake
• Regular exercise
• Establish regular defecation habit (morning after breakfast)
• Respond promptly to defecation urge
• Discontinue constipating drugs (opioids, anticholinergics, iron, calcium channel blockers)

Pharmacological Management (Step-wise)

• Ispaghula (Psyllium/Isabgol) - safest; 1-2 teaspoons with water twice daily
• Methylcellulose
• Onset 12-72 hours; good long-term safety profile

• Lactulose 15-30 mL BD - for chronic constipation; safe long-term
• PEG (Macrogol) - for severe/refractory constipation
• Magnesium hydroxide - for short-term

• Docusate sodium - when straining must be avoided (post-MI, post-surgery)

• Bisacodyl 10 mg oral or suppository
• Senna 7.5-15 mg at bedtime
• NOT for long-term use (cathartic colon, dependence)

• Phosphate enema, glycerin suppository - for impaction
• Useful for acute fecal impaction

• Opioid-induced constipation: Methylnaltrexone (peripheral mu-opioid receptor antagonist); also stimulant laxatives
• Pediatric constipation: Lactulose, PEG
• Constipation in pregnancy: Bulk-forming agents, lactulose (safe); avoid stimulant laxatives
• Hepatic encephalopathy: Lactulose (reduces ammonia)
• Post-operative/post-MI: Docusate sodium (avoid straining)

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Q18. Classify drugs used in diarrhoea. Write a note on ORS with reference to its composition, rationale, advantages and therapeutic uses.

Classification of Drugs Used in Diarrhoea

• Oral Rehydration Solution (ORS)
• IV fluids (Ringer's lactate, Normal saline, Dextrose saline)

• Opioids: Diphenoxylate, Loperamide, Codeine
• Alpha2 agonist: Clonidine (for diabetic diarrhoea)

• Kaolin, Pectin, Chalk (calcium carbonate), Activated charcoal

• Bismuth subsalicylate
• Enkephalinase inhibitors: Racecadotril (Acetorphan) - drug of choice in children
• Octreotide (for secretory diarrhea, VIPoma, carcinoid)

• Antibiotics: Cotrimoxazole, Ciprofloxacin, Metronidazole, Doxycycline (cholera), Azithromycin
• Antiprotozoal: Metronidazole, Tinidazole, Furazolidone

• Lactobacillus, Saccharomyces boulardii

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Oral Rehydration Solution (ORS)

Background

• Developed in the 1960s-70s; described as "potentially the most important medical advance of the 20th century."
• Based on the discovery that glucose-coupled sodium transport in the intestine (via SGLT1) remains intact even in severe secretory diarrhoea.

Composition (WHO/UNICEF ORS 2004 - Reduced Osmolarity ORS):

• Na+ 90 mmol/L, Glucose 111 mmol/L, osmolarity 311 mOsm/L (now replaced by reduced osmolarity ORS)

Rationale / Scientific Basis

• In diarrhoea, Na+ is lost in the stool (along with water, K+, bicarbonate/citrate).
• Normally, glucose and Na+ are cotransported across the intestinal epithelium by the SGLT1 transporter (sodium-glucose linked transporter 1).
• This transporter is NOT inactivated by the cholera toxin or enterotoxins.
• Glucose facilitates Na+ absorption via SGLT1, and water follows Na+ passively.
• Citrate (replaces bicarbonate): corrects metabolic acidosis; more stable than bicarbonate in storage.
• K+: replaces stool losses; prevents hypokalemia.
• Reduced osmolarity (245 mOsm/L vs. old 311 mOsm/L): reduces stool output by 20% and reduces vomiting compared to old WHO ORS.

Advantages

1. Can be prepared at home/peripheral settings - inexpensive, simple.
2. Given orally - no need for IV cannulation/hospitalization.
3. Replaces all electrolytes lost in diarrhoea.
4. Corrects metabolic acidosis (citrate is metabolized to bicarbonate).
5. Reduced osmolarity ORS reduces stool volume and duration of diarrhoea.
6. Safe in all ages - neonates, infants, elderly.
7. Reduces mortality from acute diarrheal dehydration dramatically.
8. Rice ORS, cereal-based ORS - provide additional substrate.

Therapeutic Uses

1. Acute diarrhoea with mild-moderate dehydration (1st line)
2. Cholera - mandatory (large volume ORS needed; IV if severe)
3. Acute gastroenteritis in infants/children
4. Prevention of dehydration in traveller's diarrhea
5. NOT a substitute for IV fluids in severe dehydration with shock, persistent vomiting, ileus

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Q19. Classify drugs used in diarrhoea. Discuss antimotility drugs.

Antimotility Drugs

1. Loperamide

• Synthetic opioid; binds to mu (μ) opioid receptors in the enteric nervous system.
• Reduces peristalsis and increases intestinal transit time - allows more water and electrolyte absorption.
• Increases anal sphincter tone - reduces urgency.
• Decreases intestinal secretion by reducing cAMP.
• Does NOT cross the BBB (P-glycoprotein pump exports it) - no CNS/analgesic/abuse effects.

• Acute non-specific diarrhoea (traveller's diarrhoea - drug of choice)
• Chronic diarrhoea (IBS with diarrhea predominance)
• Ileostomy/colostomy patients (reduce stool volume)
• Crohn's disease (adjunct)

• Constipation, abdominal distension, nausea
• Toxic megacolon (contraindicated in inflammatory diarrhoea, pseudomembranous colitis, bloody diarrhoea - can worsen by retaining toxins)
• Avoid in children <2 years
• No CNS or abuse potential at therapeutic doses

2. Diphenoxylate

• Synthetic opioid derivative; activates intestinal mu opioid receptors - reduces motility and secretion.
• Combined with atropine (Lomotil) to discourage abuse (atropine causes unpleasant effects at high doses).
• Can cross BBB in overdose - causes CNS depression.
• Less potent than loperamide.

3. Codeine

• Natural opioid; reduces GI motility.
• Has analgesic and CNS effects.
• Used for diarrhoea associated with irritable bowel syndrome.
• Adverse effects: Constipation, sedation, addiction potential.

4. Clonidine (Alpha-2 agonist)

• Used in diabetic diarrhoea and opioid withdrawal diarrhoea.
• Mechanism: Alpha-2 agonist reduces intestinal secretion and increases absorption.

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Q20. Classify drugs used in diarrhoea. Discuss antisecretory drugs used in diarrhoeal disorders.

Antisecretory Drugs in Diarrhoeal Disorders

1. Racecadotril (Acetorphan) - Drug of Choice in Children

• Inhibits enkephalinase (neutral endopeptidase, neprilysin) - the enzyme that degrades endogenous enkephalins in the gut.
• Increased enkephalins activate delta (δ) opioid receptors on intestinal secretory cells.
• Delta opioid receptor activation reduces adenylyl cyclase activity → reduces cAMP → reduces Cl- secretion and water secretion.
• Purely antisecretory - does NOT reduce intestinal motility (unlike loperamide).
• Does NOT cause constipation or risk of toxic megacolon.

• Acute secretory diarrhoea in children (drug of choice - safe, effective)
• Traveller's diarrhoea in adults
• Combined with ORS

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2. Bismuth Subsalicylate

• Anti-secretory: Salicylate component inhibits prostaglandin synthesis, reducing mucosal secretion.
• Anti-inflammatory effect in intestinal mucosa.
• Antimicrobial: Bismuth kills H. pylori and some enteric pathogens.
• Adsorbent properties.

• Traveller's diarrhoea (prophylaxis and treatment)
• H. pylori eradication
• Non-specific diarrhoea

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3. Octreotide (Somatostatin Analogue)

• Binds to somatostatin receptors on intestinal epithelium and enteroendocrine cells.
• Inhibits secretion of GI peptides (VIP, glucagon, 5-HT, gastrin, secretin).
• Reduces intestinal water and electrolyte secretion.
• Reduces splanchnic blood flow; slows GI motility.

• Secretory diarrhoea due to VIPoma, carcinoid syndrome, gastrinoma (Zollinger-Ellison)
• Short bowel syndrome (reduce fluid losses)
• AIDS-related diarrhoea
• Refractory chemotherapy-induced diarrhoea
• Acromegaly (reduces GH levels)
• Esophageal variceal bleeding (reduces portal pressure)

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4. Zinc Supplementation (Adjunct in Children)

• Reduces severity and duration of diarrhoea.
• WHO recommendation: 20 mg/day for 10-14 days in children with acute diarrhoea.
• Mechanism: Improves intestinal absorption, immune function, mucosal repair.

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Q21. Classify drugs used in diarrhoea and discuss the pharmacological management of acute diarrhoea.

Pharmacological Management of Acute Diarrhoea

Assessment First

• Severity of dehydration (mild, moderate, severe)
• Presence of blood/mucus in stool (dysentery vs. secretory)
• Duration (>14 days = persistent diarrhoea)
• Travel history, antibiotic history
• Identify cause if possible

Step 1: Fluid and Electrolyte Replacement (MOST IMPORTANT)

• ORS - for mild to moderate dehydration (as detailed in Q18)
• IV fluids (Ringer's lactate or normal saline) - for severe dehydration, shock, persistent vomiting, ileus
• Continue breastfeeding in infants; avoid prolonged fasting

Step 2: Zinc Supplementation (Children)

• 20 mg/day for 10-14 days (WHO recommendation)

Step 3: Dietary Management

• BRAT diet (Banana, Rice, Applesauce, Toast) in mild cases
• Resume normal diet as soon as possible to provide nutrients for mucosal repair

Step 4: Antimotility Drugs (Adults only, non-inflammatory diarrhoea)

• Loperamide - for traveller's diarrhoea, non-inflammatory diarrhoea in adults
• Reduce urgency and stool frequency
• Contraindicated in bloody/inflammatory diarrhoea, febrile diarrhoea, cholera

Step 5: Antisecretory Agents

• Racecadotril - preferred in children (antisecretory, does not cause constipation)
• Bismuth subsalicylate - for traveller's diarrhoea in adults

Step 6: Antimicrobial Therapy (only when indicated)

• Not all diarrhoea requires antibiotics (most viral; self-limiting)
• Indications: Cholera, bloody diarrhoea (dysentery), immunocompromised, persistent diarrhoea with identified pathogen

Step 7: Probiotics (Adjunct)

• Lactobacillus GG, Saccharomyces boulardii - reduce duration by 1 day; safe in children

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RESPIRATORY SYSTEM - LONG ANSWER QUESTIONS (10 Marks Each)

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Q1. Define bronchial asthma. Classify drugs used in bronchial asthma. Discuss the pharmacological actions, therapeutic uses and adverse effects of corticosteroids. Add a note on status asthmaticus.

Definition of Bronchial Asthma

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Classification of Drugs Used in Bronchial Asthma

• Short-Acting (SABA): Salbutamol (Albuterol), Terbutaline, Fenoterol
• Long-Acting (LABA): Salmeterol, Formoterol, Bambuterol

• Theophylline, Aminophylline, Doxofylline

• Short-acting: Ipratropium bromide
• Long-acting: Tiotropium bromide

• Inhaled: Beclomethasone, Budesonide, Fluticasone, Ciclesonide
• Systemic: Prednisolone, Hydrocortisone, Dexamethasone

• Receptor antagonists: Montelukast, Zafirlukast
• Synthesis inhibitors: Zileuton

• Sodium cromoglycate (Cromolyn)
• Nedocromil sodium

• Anti-IgE: Omalizumab
• Anti-IL-5: Mepolizumab, Reslizumab, Benralizumab
• Anti-IL-4/IL-13: Dupilumab

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Corticosteroids in Bronchial Asthma

Mechanism of Action (Anti-inflammatory mechanisms)

1. Bind to intracellular glucocorticoid receptors (GCRs) and translocate to the nucleus.
2. Bind to glucocorticoid response elements (GRE) - activate anti-inflammatory genes (annexin-1, beta2-adrenergic receptors, IkB-alpha, secretory leukoprotease inhibitor).
3. Transrepression - GCR complexes bind to transcription factors (NF-kB, AP-1) and block transcription of pro-inflammatory genes (cytokines, enzymes).
4. Reduce the production of inflammatory mediators:
   • Inhibit synthesis of leukotrienes, prostaglandins (by inducing lipocortin/annexin-1, which inhibits phospholipase A2)
   • Reduce cytokines (IL-1, IL-2, IL-4, IL-5, IL-6, IL-8, TNF-alpha)
   • Reduce chemokines (CCL5, IL-8)
5. Reduce mucosal edema and mucus hypersecretion.
6. Reduce number and activation of eosinophils, mast cells, macrophages, T-lymphocytes in airway mucosa.
7. Upregulate beta-2 adrenergic receptors (restores responsiveness to beta-2 agonists).
8. Reduce airway hyperresponsiveness over weeks to months.

Therapeutic Uses

• Beclomethasone dipropionate 100-800 mcg/day (MDI)
• Budesonide 200-800 mcg/day (Turbuhaler or MDI)
• Fluticasone propionate (100-500 mcg/day) - most potent
• Ciclesonide - prodrug activated in lungs; less systemic absorption

1. Moderate to severe persistent asthma - first-line controller therapy
2. Step-up therapy when SABA alone insufficient
3. Prevent asthma exacerbations
4. Exercise-induced asthma (prophylaxis)
5. Often combined with LABA (Budesonide/Formoterol - Symbicort; Fluticasone/Salmeterol - Seretide)

• Prednisolone 30-60 mg/day oral for acute exacerbations (5-7 day course)
• IV Hydrocortisone 100-200 mg Q4H or IV Methylprednisolone for status asthmaticus
• Long-term oral steroids: Only for severe, steroid-dependent asthma (last resort)

Adverse Effects

1. Oral candidiasis (thrush) - most common; prevented by rinsing mouth after use + spacer device
2. Dysphonia (hoarseness of voice) - due to local myopathy of laryngeal muscles
3. Reflex cough and bronchospasm (rare - using spacer reduces)

1. Cushingoid features (moon face, buffalo hump, truncal obesity)
2. Osteoporosis, pathological fractures
3. Hyperglycemia, diabetes mellitus
4. Hypertension, sodium/water retention, hypokalemia
5. Peptic ulcer, gastritis
6. Growth retardation in children
7. Immunosuppression, susceptibility to infections (tuberculosis reactivation)
8. Cataracts and glaucoma
9. Myopathy, proximal muscle weakness
10. Psychiatric effects: euphoria, psychosis, depression
11. Adrenal suppression - abrupt withdrawal causes Addisonian crisis

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Status Asthmaticus

1. Oxygen therapy - high flow O2 to maintain SpO2 93-95%
2. SABA (Salbutamol) - nebulized 2.5-5 mg q20 min × 3 doses (or continuous) or MDI via spacer
3. Ipratropium bromide - nebulized 0.5 mg with salbutamol (combination has synergistic effect)
4. Systemic corticosteroids - IV hydrocortisone 200 mg stat (or methylprednisolone 125 mg IV) → oral prednisolone 40-60 mg/day for 5-7 days; start within 1 hour
5. IV Magnesium sulphate 1.2-2 g over 20 min - bronchodilator (blocks Ca2+ channels in bronchial smooth muscle); used in life-threatening attacks
6. IV Aminophylline - if poor response (5 mg/kg loading dose over 20 min, then 0.5 mg/kg/hr); increasingly replaced by Mg sulphate
7. Heliox (helium-oxygen mixture) - reduces airway resistance in severe obstruction
8. Intubation and mechanical ventilation - if life-threatening (PaCO2 rising, exhaustion, altered consciousness)

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Q2. Define bronchial asthma. Classify drugs used in bronchial asthma. Discuss the mechanism of action, therapeutic uses and adverse effects of Beta2-adrenergic agonists.

Beta-2 Adrenergic Agonists

• Short-acting (SABA): Salbutamol, Terbutaline, Fenoterol, Pirbuterol (onset 5-10 min, duration 3-6 hours)
• Long-acting (LABA): Salmeterol (onset 20-30 min, duration 12 hours), Formoterol (onset 3-5 min, duration 12 hours), Bambuterol (prodrug of terbutaline)
• Ultra-long-acting: Indacaterol, Vilanterol, Olodaterol (once daily)

Mechanism of Action

1. Selectively activate beta-2 adrenergic receptors (Gs-coupled) on bronchial smooth muscle cells.
2. Adenylyl cyclase → increased cAMP → activation of protein kinase A (PKA).
3. PKA phosphorylates:
   • Myosin light chain kinase (MLCK) - inactivated → smooth muscle relaxation
   • Large conductance K+ (BKCa) channels - opens → hyperpolarization → relaxation
   • Reduces intracellular Ca2+ → bronchial smooth muscle relaxation = bronchodilation
4. Additional anti-inflammatory effects (especially LABA):
   • Reduces mast cell mediator release
   • Inhibits microvascular leakage
   • Enhances mucociliary clearance
   • Upregulates beta-2 receptors (in combination with corticosteroids)
5. SABAs: Drug of choice for acute bronchospasm (RELIEVER therapy)
6. LABAs: Added to ICS for inadequate control (never as monotherapy in asthma - must always combine with ICS)

Therapeutic Uses

1. Acute bronchospasm in asthma - drug of choice (reliever)
2. Status asthmaticus (nebulized salbutamol 2.5-5 mg)
3. Exercise-induced asthma (preventive - 2 puffs before exercise)
4. COPD exacerbations
5. Hyperkalemia (IV salbutamol or nebulized) - drives K+ into cells
6. Preterm labor (tocolysis) - Terbutaline (relaxes uterine smooth muscle)

1. Moderate to severe persistent asthma - as add-on to ICS (never alone in asthma)
2. COPD (maintenance therapy)
3. Nocturnal asthma symptoms
4. Exercise-induced asthma prophylaxis
5. Available as fixed-dose combinations: Fluticasone+Salmeterol (Seretide), Budesonide+Formoterol (Symbicort)

Adverse Effects

1. Tachycardia, palpitations (due to residual beta-1 stimulation and reflex from vasodilation)
2. Tremor (skeletal muscle beta-2 stimulation) - most common complaint
3. Hypokalemia - beta-2 stimulation drives K+ into cells; dangerous with diuretics
4. Hyperglycemia - beta-2 stimulation promotes glycogenolysis
5. Headache, dizziness
6. Paradoxical bronchospasm - rare but serious; use alternative bronchodilator
7. Tolerance/tachyphylaxis - with excessive SABA use; downregulation of beta-2 receptors
8. QTc prolongation - at high doses
9. Hypomagnesemia - with prolonged high-dose nebulized therapy
10. LABAs safety concern: When used WITHOUT ICS in asthma, associated with increased asthma-related deaths (BLACK BOX WARNING in USA). Must ALWAYS combine LABA with ICS in asthma.

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Q3. Define bronchial asthma. Classify drugs. Discuss the pharmacological actions, therapeutic uses and adverse effects of methylxanthines.

Methylxanthines

Mechanism of Action (Multiple Mechanisms)

1. Phosphodiesterase (PDE) inhibition (Main mechanism):
   • Inhibit PDE3 and PDE4 enzymes that break down cAMP and cGMP.
   • Increased cAMP → PKA activation → smooth muscle relaxation → bronchodilation.
   • Reduced mediator release from mast cells and eosinophils.
2. Adenosine receptor antagonism:
   • Competitively block adenosine A1 and A2 receptors.
   • Adenosine is bronchoconstrictive and mediates many effects in asthma.
   • CNS stimulation (caffeine-like) via adenosine antagonism.
3. Stimulate catecholamine release from adrenal medulla - contributes to bronchodilation.
4. Anti-inflammatory effects (at therapeutic doses):
   • Inhibit inflammatory cell recruitment.
   • Histone deacetylase (HDAC) activation - deacetylates histones, switches off inflammatory genes.
   • Reduces IL-5, IL-4, TNF-alpha production.
5. Increased diaphragmatic contractility - useful in respiratory failure.
6. Stimulate mucociliary clearance.
7. CNS stimulation - increases respiratory drive (useful in apnea of prematurity).

Pharmacokinetics

• Well absorbed orally; sustained-release forms available.
• Metabolized by CYP1A2 (80%) and CYP3A4.
• Narrow therapeutic index: Therapeutic range = 10-20 mcg/mL. Toxic effects at >20 mcg/mL.
• Half-life variable (4-12 hours); increased in: liver disease, heart failure, elderly, obesity, ciprofloxacin/erythromycin use; decreased in: smokers, children, rifampicin use.

Therapeutic Uses

1. Bronchial asthma - third-line after beta-2 agonists and corticosteroids
   • Sustained-release theophylline - for nocturnal asthma (maintenance)
   • IV Aminophylline - for status asthmaticus (second-line; being replaced by Mg sulphate)
2. COPD - maintenance therapy (improves airflow, reduces exacerbations)
3. Apnea of prematurity - Caffeine citrate IV (drug of choice in neonates for respiratory stimulation)
4. Cheyne-Stokes respiration (nocturnal apnea in heart failure)

Adverse Effects (Dose-related - correlate with plasma levels)

• Nausea, vomiting, diarrhea (GI disturbances - most common)
• Headache, dizziness, irritability, restlessness, insomnia (CNS stimulation)
• Tachycardia, palpitations

• Severe nausea, vomiting
• Sinus tachycardia, supraventricular tachycardia
• Hypokalemia (via beta-adrenergic stimulation)

• Seizures (may be the first sign; potentially fatal)
• Ventricular arrhythmias (VT, VF)
• Hypotension, cardiovascular collapse

• Levels INCREASED by: Cimetidine, Erythromycin, Ciprofloxacin, Allopurinol, Oral contraceptives (reduce metabolism - risk of toxicity)
• Levels DECREASED by: Rifampicin, Phenytoin, Carbamazepine, Smoking (induce CYP1A2 - sub-therapeutic levels)

• Diuresis (inhibits ADH action)
• Fine tremors

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Q4. Define bronchial asthma. Classify drugs. Discuss the mechanism of action, therapeutic uses and adverse effects of anticholinergic bronchodilators.

Anticholinergic Bronchodilators (Muscarinic Antagonists)

• Short-acting: Ipratropium bromide (SAMA) - 4-6 hour duration
• Long-acting: Tiotropium bromide (LAMA) - 24 hour duration; Glycopyrronium, Umeclidinium, Aclidinium

Mechanism of Action

• Airways receive predominantly parasympathetic (vagal/cholinergic) innervation.
• Acetylcholine activates M3 muscarinic receptors on bronchial smooth muscle and submucosal glands.
• M3 activation → Gq protein → PLC activation → increased IP3/DAG → increased intracellular Ca2+ → smooth muscle contraction (bronchoconstriction) + increased mucus secretion.
• Anticholinergics competitively block M3 receptors → prevent bronchoconstriction and reduce mucus secretion → bronchodilation.
• Tiotropium also blocks M1 receptors (which facilitate ACh release at ganglia - their blockade further reduces cholinergic tone).
• Tiotropium: kinetically selective for M3 over M2 receptors (M2 blockade would increase ACh release and counteract benefit - tiotropium's slow dissociation from M3 but fast from M2 is advantageous).
• Less potent bronchodilators than beta-2 agonists in asthma (because cholinergic tone is less important in asthma), but comparable to or superior in COPD (where increased vagal tone plays a bigger role).

Therapeutic Uses

1. COPD - first-line bronchodilator; superior to beta-2 agonists in some COPD patients
2. Bronchial asthma - combined with salbutamol in acute/severe exacerbations (Combivent); additive bronchodilation via different mechanisms
3. Status asthmaticus - nebulized ipratropium + salbutamol combination (more effective than either alone)
4. Rhinorrhoea in perennial rhinitis (intranasal ipratropium)
5. Common cold-induced rhinorrhoea

1. COPD - drug of choice for maintenance therapy (GOLD guidelines); once-daily inhaler
2. Severe persistent asthma - add-on therapy (tiotropium Respimat)
3. Reduces COPD exacerbations and hospitalizations
4. Improves exercise tolerance and quality of life in COPD

Adverse Effects

1. Dry mouth - most common (oropharyngeal deposition)
2. Bitter metallic taste (ipratropium)
3. Blurred vision - if powder enters eyes; angle-closure glaucoma - use spacer; avoid spraying near eyes
4. Urinary retention - rare; caution in BPH

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Q5. Classify drugs used in bronchial asthma. Discuss bronchodilators with suitable examples.

Bronchodilators - Comprehensive Discussion

I. Beta-2 Adrenergic Agonists

• SABAs (Salbutamol, Terbutaline) - RELIEVERS
• LABAs (Salmeterol, Formoterol) - CONTROLLERS (always with ICS)

II. Anticholinergics (Muscarinic Antagonists)

• Ipratropium (SAMA)
• Tiotropium (LAMA)

III. Methylxanthines

• Theophylline, Aminophylline

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Q6. Classify drugs used in bronchial asthma. Discuss leukotriene modifiers and mast cell stabilizers. Add a short note on biological agents used in bronchial asthma.

Leukotriene Modifiers

Classification of Leukotriene Modifiers:

1. Cysteinyl Leukotriene (CysLT1) Receptor Antagonists (LTRAs):
   • Montelukast (once daily, oral), Zafirlukast (twice daily)
2. 5-Lipoxygenase Inhibitors (reduce leukotriene synthesis):
   • Zileuton (inhibits 5-LOX enzyme)

Mechanism of Action

• Competitively block CysLT1 receptors on bronchial smooth muscle and inflammatory cells.
• Prevent the actions of LTC4, LTD4, LTE4: bronchoconstriction, edema, mucus secretion, eosinophil recruitment.

• Inhibits 5-lipoxygenase enzyme → blocks synthesis of all leukotrienes (LTA4, LTB4, and cysteinyl leukotrienes).

Therapeutic Uses (Montelukast)

1. Mild to moderate persistent asthma - as add-on to ICS or alternative to ICS in mild asthma
2. Exercise-induced asthma - effective prophylaxis (taken 2 hours before exercise)
3. Aspirin/NSAID-sensitive asthma - particularly effective (NSAIDs shunt arachidonic acid to lipoxygenase pathway, increasing leukotrienes)
4. Allergic rhinitis (dual benefit - reduces nasal and bronchial symptoms)
5. Seasonal and perennial allergic rhinitis
6. Combined with H1 antihistamine for urticaria

Adverse Effects

• Montelukast: Generally well-tolerated; headache, nausea, hepatotoxicity (rare), eosinophilic vasculitis (Churg-Strauss syndrome - rare, associated with steroid withdrawal)
• Neuropsychiatric effects (FDA warning 2020): mood changes, suicidality, sleep disturbances, nightmares
• Zileuton: Hepatotoxicity (LFT monitoring required), nausea

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Mast Cell Stabilizers

Mechanism of Action

• Inhibit the degranulation of mast cells by stabilizing the mast cell membrane.
• Block Cl- channels in mast cell membranes → prevent Ca2+ entry → prevent mast cell degranulation.
• Prevent the release of inflammatory mediators: histamine, leukotrienes, prostaglandins, PAF, bradykinin, cytokines.
• Also inhibit sensory nerve activation (reduce neurogenic inflammation).
• NO direct bronchodilator action - purely preventive/prophylactic.
• Nedocromil also inhibits eosinophil and neutrophil activation.

Therapeutic Uses

1. Mild persistent asthma - prophylactic controller therapy (before ICS was widely used)
2. Exercise-induced asthma - inhale 15-20 minutes before exercise
3. Allergen-induced (seasonal) asthma - before allergen exposure
4. Allergic rhinitis (intranasal cromoglycate drops)
5. Vernal keratoconjunctivitis (eye drops)
6. Food allergy (oral cromolyn)

Adverse Effects

• Extremely well-tolerated - no systemic side effects
• Local: Throat irritation, cough, bronchospasm (transient - on inhalation of dry powder)
• Unpleasant taste (nedocromil)

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Biological Agents in Bronchial Asthma

1. Omalizumab (Anti-IgE)

• Humanized monoclonal antibody against free IgE.
• Binds free IgE, preventing it from binding to FcεRI receptors on mast cells and basophils → prevents mast cell sensitization and degranulation.
• Also downregulates FcεRI receptor expression.
• Uses: Severe allergic (IgE-mediated) asthma with elevated serum IgE; allergic rhinitis; chronic urticaria.
• Given SC every 2-4 weeks.
• Adverse effects: Injection site reactions, anaphylaxis (rare but requires 2-hour observation after each dose).

2. Anti-IL-5 Agents (for Eosinophilic Asthma)

• Mepolizumab (anti-IL-5 monoclonal antibody) - prevents IL-5 binding to eosinophil receptor → reduces eosinophil survival and activation.
• Reslizumab (anti-IL-5) - IV infusion
• Benralizumab (anti-IL-5Rα receptor antibody) - blocks IL-5 receptor; also causes direct eosinophil depletion (ADCC)
• Uses: Severe eosinophilic asthma (blood eosinophils >300 cells/mcL)
• Reduce asthma exacerbations and allow oral steroid dose reduction.

3. Dupilumab (Anti-IL-4Rα)

• Monoclonal antibody against IL-4 receptor alpha subunit - blocks both IL-4 and IL-13 signaling.
• Uses: Moderate-severe type 2 inflammatory (eosinophilic or allergic) asthma, also for atopic dermatitis, chronic rhinosinusitis with nasal polyps.
• Given SC every 2 weeks.

4. Tezepelumab (Anti-TSLP)

• Blocks thymic stromal lymphopoietin (TSLP) - an upstream alarm cytokine from epithelial cells that drives type 2 inflammation.
• Broad-spectrum biologic - works in eosinophilic and non-eosinophilic asthma.
• Recently approved; reduces exacerbations across all phenotypes.

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Q7. Classify drugs used in cough. Discuss antitussives with reference to their mechanism of action, therapeutic uses and adverse effects.

Classification of Drugs Used in Cough

• Opioid type: Codeine, Pholcodine, Hydrocodone
• Non-opioid type: Dextromethorphan, Noscapine (Narcotine), Benzonatate, Chlophedianol

• Guaiphenesin (Guaifenesin), Ammonium chloride, Sodium/Potassium citrate, Tolu balsam, Terpin hydrate

• N-Acetylcysteine, Bromhexine, Ambroxol, Carbocisteine (S-Carboxymethylcysteine), Dornase alfa

• Glycerin, Honey, Syrup, Liquorice

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Antitussives

1. Codeine (Prototype Opioid Antitussive)

• Activates mu opioid receptors in the cough center in the medulla oblongata (nucleus tractus solitarius) → depresses the cough reflex directly.
• Also acts peripherally on opioid receptors in the airways.
• Has both antitussive and analgesic properties.
• About 10% converted to morphine in liver by CYP2D6.
• Dose for cough: 10-30 mg (lower than analgesic dose); can suppress cough without significant analgesia.

1. Non-productive (dry, irritating) cough - short-term
2. Post-operative cough
3. Cough in terminal cancer/palliative care
4. Mild pain (analgesic)
5. Diarrhea (antidiarrheal)

1. Constipation (very common)
2. Nausea, vomiting
3. Sedation, drowsiness
4. Respiratory depression (at high doses)
5. Dependence and abuse potential (codeine abuse - converting to morphine)
6. Poor metabolizers (CYP2D6 deficient) - no benefit
7. Ultra-rapid metabolizers - risk of overdose
8. Contraindicated in children <12 years (ultra-rapid morphine conversion)

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2. Dextromethorphan (DXM) - Non-Opioid Antitussive

• D-isomer of methorphan (levomethorphan is opioid).
• Acts on sigma receptors and NMDA receptor channels (non-competitive antagonist) in the cough center.
• At therapeutic doses: No opioid activity, no analgesia, no respiratory depression, no dependence.
• At high doses: Dissociative/hallucinogenic effects (NMDA antagonism) - misused recreationally.

1. Dry, non-productive cough (OTC use)
2. Short-term cough in adults and children (>12 years; avoid in young children)

• Generally safe at therapeutic doses
• Dizziness, drowsiness, nausea (mild)
• Serotonin syndrome with MAO inhibitors (avoid combination)
• Abuse potential at high doses (euphoria, hallucinations)

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3. Noscapine (Narcotine) - Non-Opioid, Non-Sedating

• Natural opium alkaloid but no opioid receptor activity.
• Antitussive mechanism: Possibly via sigma receptors; vagal sensory nerve depression.
• No analgesia, no sedation, no dependence.
• Has anti-tumor properties (investigational).

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4. Benzonatate (Tessalon)

• Local anesthetic (related to tetracaine).
• Anesthetizes the stretch receptors in the lungs and pleura → reduces afferent signals to the cough center.
• No CNS opioid effects.

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Q8. Classify drugs used in cough. Discuss expectorants and mucolytic agents with suitable examples.

Expectorants

1. Guaifenesin (Guaiphenesin) - Most widely used

• Acts on the gastric mucosa → triggers a vagal reflex → stimulates secretion of respiratory tract fluid (bronchial glands).
• Increases the volume of sputum and reduces its viscosity (dilutes secretions).
• Stimulates cilia to clear secretions.
• At high doses: direct irritant effect on bronchial mucosa.

• Productive cough to facilitate expectoration
• Chest congestion, bronchitis, URTI
• Available in many OTC cough-cold preparations (Robitussin)

2. Ammonium Chloride

3. Sodium/Potassium Citrate

• Alkalinizes urine; mild expectorant properties.
• Less effective than guaifenesin.

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Mucolytic Agents

1. N-Acetylcysteine (NAC)

• Contains free sulfhydryl (-SH) groups.
• Breaks disulfide bonds (-S-S-) in mucus glycoproteins, depolymerizing mucin macromolecules → reduces viscosity.
• Antioxidant: Precursor of glutathione → replenishes intracellular glutathione in oxidative stress.

1. COPD (chronic bronchitis) - reduces viscosity of secretions
2. Cystic fibrosis - mucus clearance
3. Paracetamol (acetaminophen) overdose - antidote (replenishes glutathione to detoxify NAPQI)
4. Contrast nephropathy prophylaxis (renal protection)
5. Prevention of COPD exacerbations (long-term)

2. Bromhexine

• Depolymerizes mucopolysaccharide fibers in sputum (lyses the fibrous gel network of sputum).
• Increases volume of bronchial secretion (secretolytic effect) while reducing viscosity.
• Stimulates production of serous mucus (less viscous), replacing viscous mucoid secretions.
• Stimulates ciliary activity.
• Prodrug: Converted in liver to Ambroxol (active metabolite - more potent).

1. Chronic bronchitis, COPD
2. Bronchiectasis
3. Cystic fibrosis
4. Productive cough with viscous secretions

3. Ambroxol

• Active metabolite of bromhexine; more potent.
• Also stimulates surfactant synthesis by type II pneumocytes (useful in neonatal respiratory distress).

4. Carbocisteine (S-Carboxymethylcysteine)

• Reduces mucus viscosity by altering glycoprotein structure.
• Restores normal ratio of sialomucins to fucomucins in bronchial secretions.
• Reduces exacerbations in COPD.

5. Dornase Alfa (DNase I - Recombinant)

• Cleaves extracellular DNA (released from degenerating neutrophils) in purulent secretions.
• Specifically used in cystic fibrosis (sputum in CF contains large amounts of DNA).
• Given by nebulization once daily.
• Reduces exacerbations in CF, improves lung function.
• Adverse effects: Hoarseness, pharyngitis, laryngitis, rash.

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Q9. Classify mucolytic agents. Discuss the pharmacological actions, therapeutic uses and adverse effects of acetylcysteine and bromhexine.

• Thiol group: N-Acetylcysteine, Carbocisteine
• Synthetic: Bromhexine, Ambroxol
• Enzyme: Dornase alfa
• Physical: Saline nebulization, Steam inhalation

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Q10. Classify drugs used in allergic rhinitis. Discuss antihistamines with reference to their mechanism of action, therapeutic uses and adverse effects.

Classification of Drugs Used in Allergic Rhinitis

• First generation: Chlorpheniramine (CPM), Promethazine, Diphenhydramine, Pheniramine
• Second generation: Cetirizine, Loratadine, Fexofenadine, Levocetirizine, Desloratadine, Rupatadine, Bilastine

• Topical: Oxymetazoline, Xylometazoline (alpha-1 agonists)
• Oral: Pseudoephedrine, Phenylephrine

• Budesonide, Fluticasone, Beclomethasone, Mometasone, Triamcinolone

• Intranasal Sodium cromoglycate

• Intranasal Ipratropium bromide (for rhinorrhoea)

• Montelukast (especially when combined with asthma)

• Omalizumab (severe allergic rhinitis)

• Subcutaneous immunotherapy (SCIT), Sublingual immunotherapy (SLIT)

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Antihistamines (H1 Receptor Antagonists)

Mechanism of Action

• Competitively block histamine H1 receptors on target cells.
• Histamine (released from mast cells/basophils on allergen cross-linking with surface IgE) activates H1 receptors causing: vasodilation, increased vascular permeability (edema, rhinorrhoea), smooth muscle contraction (bronchospasm, gut cramps), pruritus, stimulation of sensory nerve endings (itch).
• H1 antagonists prevent all H1-mediated effects.
• Inverse agonism: Modern antihistamines are actually inverse agonists at H1 receptors (stabilize the inactive receptor conformation), not just neutral antagonists.

• Cross the BBB readily (lipophilic) → block central H1 receptors → sedation, impaired cognition.
• Also block muscarinic, alpha-adrenergic, and serotonin receptors.

• Less lipophilic; poor BBB penetration; substrates for P-glycoprotein efflux pump.
• Selective H1 blockade with minimal CNS or anticholinergic effects.
• Cetirizine, Levocetirizine may cause mild sedation in some individuals.
• Fexofenadine: Least sedating; actively pumped out of CNS by P-gp.

Therapeutic Uses of Antihistamines

1. Allergic rhinitis (seasonal and perennial) - 2nd generation preferred (non-sedating)
2. Urticaria (acute and chronic) - most effective; 2nd generation preferred
3. Allergic conjunctivitis (topical and systemic)
4. Anaphylaxis - adjuvant (diphenhydramine IV/IM); NOT for acute life-threatening anaphylaxis (epinephrine is primary)
5. Insect bites and stings - pruritus, local reaction
6. Contact/atopic dermatitis - to relieve pruritus (1st generation may help sedation at night)
7. Motion sickness - 1st generation: Promethazine, Cinnarizine, Dimenhydrinate (via H1 and M blockade in vestibular apparatus)
8. Nausea and vomiting - Promethazine (PONV, pregnancy)
9. Pre-medication before anesthesia - Promethazine (sedation + antiemetic)
10. Cough - Diphenhydramine (antitussive component in many syrups)
11. Insomnia - Diphenhydramine, Doxylamine (OTC sleep aids)

Adverse Effects

1. CNS Depression - sedation, drowsiness, impaired cognition, psychomotor impairment (MAJOR limitation - impairs driving, exams)
2. Paradoxical CNS stimulation - in children (excitement, hyperactivity, tremors)
3. Anticholinergic effects (due to M receptor blockade):
   • Dry mouth, blurred vision, urinary retention, constipation, tachycardia
4. Appetite stimulation, weight gain (antihistamine effect on hypothalamic H1 receptors)
5. Potentiation of CNS depressants (alcohol, sedatives, opioids)
6. Photosensitization (phenothiazine antihistamines - promethazine)
7. Extrapyramidal effects (promethazine - D2 blockade at high doses)

1. Minimal sedation (fexofenadine - least; cetirizine - some)
2. QT interval prolongation - concern with Astemizole and Terfenadine (both withdrawn); current 2nd generation drugs have better cardiac safety
3. Headache, nausea (mild)
4. Loratadine: generally very well-tolerated; no significant sedation or QT prolongation

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Q11. Discuss the pharmacological management of allergic rhinitis.

Definition

Management

1. Allergen Avoidance

• Identify and minimize exposure to triggers (dust mites, pet dander, pollen, moulds).

2. Antihistamines (H1 antagonists) - For sneezing, rhinorrhoea, pruritus, itchy eyes

• Second-generation (preferred): Cetirizine 10 mg OD, Fexofenadine 120/180 mg OD, Loratadine 10 mg OD, Levocetirizine 5 mg OD.
• Effective for sneezing, rhinorrhoea, pruritus but LESS effective for nasal congestion.
• Safe for long-term use; once daily dosing.

3. Intranasal Corticosteroids (Most effective overall - GOLD STANDARD)

• Fluticasone furoate, Mometasone furoate, Budesonide, Beclomethasone.
• 1-2 sprays each nostril OD or BD.
• Reduce all symptoms including nasal congestion.
• Onset: 12-24 hours; maximal benefit in 1-2 weeks.
• Adverse effects: Nasal dryness, crusting, epistaxis (rare); minimal systemic absorption.

4. Decongestants - For nasal congestion

• Topical (short-term <3-5 days): Oxymetazoline, Xylometazoline - alpha-1 agonists, reduce nasal mucosal engorgement.
  • Risk of rhinitis medicamentosa (rebound congestion) if used >5 days.
• Oral: Pseudoephedrine, Phenylephrine.
  • Adverse effects: Hypertension, insomnia, palpitations, urinary retention.

5. Mast Cell Stabilizers

• Intranasal Cromoglycate - prevents mast cell degranulation.
• Effective as prophylaxis before allergen exposure; less effective than ICS.
• Very safe; used in children.

6. Leukotriene Receptor Antagonists

• Montelukast 10 mg OD - effective for both allergic rhinitis and coexisting asthma.
• Less effective than intranasal corticosteroids as monotherapy.

7. Intranasal Ipratropium

• For rhinorrhoea (reduces mucus secretion).
• Anticholinergic action.

8. Systemic Corticosteroids

• Short courses (prednisolone) for severe exacerbations unresponsive to intranasal steroids.
• Not for long-term management.

9. Allergen Immunotherapy

• Subcutaneous immunotherapy (SCIT) or Sublingual immunotherapy (SLIT).
• Gradually desensitizes patient to specific allergens.
• Disease-modifying; reduces future sensitivity and prevents asthma development.

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Q12. Define COPD. Classify drugs used in COPD and discuss bronchodilators with reference to their mechanism of action, therapeutic uses and adverse effects.

Definition of COPD

• Chronic bronchitis: Chronic cough + sputum production for ≥3 months in ≥2 consecutive years.
• Emphysema: Abnormal, permanent enlargement of air spaces distal to terminal bronchioles with destruction of alveolar walls.

Classification of Drugs Used in COPD (GOLD Guidelines)

• Short-acting beta-2 agonists (SABA): Salbutamol, Terbutaline
• Long-acting beta-2 agonists (LABA): Salmeterol, Formoterol, Indacaterol
• Short-acting muscarinic antagonists (SAMA): Ipratropium
• Long-acting muscarinic antagonists (LAMA): Tiotropium, Glycopyrronium, Umeclidinium
• Methylxanthines: Theophylline, Aminophylline (third-line)
• Combinations: LABA+LAMA (Indacaterol+Glycopyrronium, Vilanterol+Umeclidinium)

• Inhaled corticosteroids (ICS): Added to LABA in patients with frequent exacerbations + eosinophilia
• Phosphodiesterase-4 inhibitor: Roflumilast (for severe COPD with chronic bronchitis + frequent exacerbations)

• Mucolytics: N-Acetylcysteine, Carbocisteine (reduce exacerbations)
• Antibiotics: Azithromycin prophylaxis (reduce exacerbations in selected patients)
• Alpha-1 antitrypsin augmentation therapy (for hereditary emphysema)
• Oxygen therapy (long-term)
• Vaccination (influenza, pneumococcal)

Bronchodilators in COPD (Mechanism, Uses, Adverse Effects)

• In COPD, bronchodilators relieve symptoms but do NOT modify disease progression (unlike asthma where ICS reduces airway remodeling).
• LAMAs (Tiotropium) are superior to LABA as first-line maintenance in COPD (cholinergic tone is the dominant reversible component in COPD).
• ICS should NOT be given to all COPD patients (unlike asthma); only added when: blood eosinophils >300/mcL, frequent exacerbations, or asthma overlap.
• LABA+LAMA combination is superior to either alone for COPD.

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Q13. Compare the pharmacological management of bronchial asthma and COPD.

Comparison: Asthma vs. COPD Management

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QUICK REFERENCE INDEX

GASTROINTESTINAL SYSTEM (Q1-21)

RESPIRATORY SYSTEM (Q1-13)

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• Questions asking to "Define X + Classify + Discuss Drug Y" follow a pattern: Definition (1-2 marks) → Classification with examples (2-3 marks) → Mechanism of Action (3 marks) → Therapeutic Uses (2 marks) → Adverse Effects (2 marks) = 10 marks
• Always write drug names in both generic and class names
• For adverse effects, always mention the MOST IMPORTANT/UNIQUE ones first (e.g., EPR for metoclopramide, antiandrogenic effects for cimetidine, constipation for aluminium hydroxide)
• ORS question always comes - memorize the exact composition (Na+ 75, K+ 20, Cl- 65, Citrate 10, Glucose 75, Osmolarity 245)

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CNS PHARMACOLOGY - ALL 19 LONG ANSWER QUESTIONS

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UNIT I - ANTIEPILEPTIC DRUGS

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Q1. Classify antiepileptic drugs. Describe Phenytoin - mechanism of action, pharmacokinetics, therapeutic uses, adverse effects, and drug interactions.

Classification of Antiepileptic Drugs (AEDs)

• Hydantoins: Phenytoin, Fosphenytoin
• Barbiturates: Phenobarbitone, Primidone
• Iminostilbenes: Carbamazepine, Oxcarbazepine
• Valproic acid: Sodium Valproate
• Succinimides: Ethosuximide
• Benzodiazepines: Diazepam, Clonazepam, Lorazepam, Clobazam
• Newer drugs: Lamotrigine, Levetiracetam, Gabapentin, Pregabalin, Topiramate, Vigabatrin, Zonisamide

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PHENYTOIN (Diphenylhydantoin)

Mechanism of Action

• Neurons fire by opening sodium (Na+) channels rapidly.
• Phenytoin selectively blocks voltage-gated Na+ channels in the inactivated (closed) state.
• It prolongs the inactivated state of Na+ channels → slows recovery → reduces the ability of neurons to fire at high frequencies.
• This is called "use-dependent" or "frequency-dependent" blockade - it preferentially blocks rapidly firing (epileptic) neurons without affecting normal neurons.
• Result: Stabilizes neuronal membranes, prevents spread of seizure discharge.
• At high concentrations: Also inhibits Ca2+ channels and modulates GABA.

Simple way to remember: "Phenytoin locks the sodium door so the neuron can't keep firing repeatedly."

Pharmacokinetics (Very Important - Non-linear kinetics!)

Key point for exam: Phenytoin shows Michaelis-Menten (non-linear/zero-order) kinetics at therapeutic doses. This means even a small dose increase can suddenly cause toxic levels - making plasma level monitoring mandatory.

Therapeutic Uses

1. Generalized tonic-clonic seizures - drug of choice (with valproate)
2. Partial (focal) seizures - simple and complex
3. Status epilepticus - IV phenytoin or fosphenytoin (given after IV benzodiazepines)
4. Post-neurosurgical seizure prophylaxis
5. Trigeminal neuralgia (second-line after carbamazepine)
6. Cardiac arrhythmias - specifically digoxin-induced ventricular arrhythmias (rarely used now; superseded by lignocaine/amiodarone)
7. NOT effective for: Absence seizures (may worsen them), myoclonic seizures

Adverse Effects

1. Gingival hyperplasia (gum overgrowth) - ~20% of patients; due to altered collagen metabolism; characteristic adverse effect of phenytoin; prevented by good oral hygiene
2. Hirsutism (increased body/facial hair) - especially troublesome in women
3. Coarsening of facial features
4. Megaloblastic anaemia - folate deficiency (reduces folate absorption + increases folate metabolism); treated with folic acid
5. Osteomalacia - induces CYP enzymes → increases Vitamin D metabolism → reduces calcium absorption; treated with Vit D
6. Peripheral neuropathy - with long-term use

1. Nystagmus - first sign of toxicity (plasma level >20 mcg/mL)
2. Ataxia (loss of balance) - level >30 mcg/mL
3. Mental confusion, diplopia - level >40 mcg/mL
4. Encephalopathy, coma - very high levels

1. Skin rashes - maculopapular; rarely Stevens-Johnson syndrome
2. Hepatotoxicity (rare)
3. Lymphadenopathy

1. Cardiovascular toxicity - hypotension, bradycardia, cardiac arrhythmias (due to propylene glycol solvent); must give slowly (<50 mg/min)
2. Purple glove syndrome - local thrombophlebitis at IV site

1. Fetal hydantoin syndrome - cleft palate, cardiac defects, facial abnormalities, nail/digital hypoplasia; Category D in pregnancy

Drug Interactions (Phenytoin is a major CYP enzyme INDUCER)

• Oral contraceptive pills (OCP) → contraceptive failure
• Warfarin → reduced anticoagulation → clotting risk
• Corticosteroids → reduced effect
• Cyclosporine → transplant rejection risk
• Digoxin → reduced levels

• Cimetidine, Isoniazid, Fluconazole, Sulphonamides (inhibit CYP2C9)
• Valproate (displaces phenytoin from protein binding + inhibits metabolism)

• Carbamazepine, Phenobarbitone (induce metabolism)
• Rifampicin

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Q2. Describe Sodium Valproate - mechanism of action, pharmacokinetics, therapeutic uses, adverse effects, and precautions.

Sodium Valproate (Valproic Acid)

Think of valproate as the "broad spectrum" antiepileptic - it works in almost all types of epilepsy.

Mechanism of Action (Multiple mechanisms - valproate's strength)

1. Na+ channel blockade (like phenytoin) - reduces repetitive firing
2. Potentiates GABA (inhibitory neurotransmitter):
   • Inhibits GABA transaminase (the enzyme that breaks down GABA) → increases GABA levels
   • Enhances GABA synthesis (activates glutamic acid decarboxylase)
   • Increases GABA release
3. Blocks T-type Ca2+ channels in thalamus (like ethosuximide) → effective for absence seizures
4. Reduces glutamate excitability

Memory tip: Valproate = "GABA booster + Na channel blocker + Ca channel blocker" = Broad spectrum drug

Pharmacokinetics

Therapeutic Uses - BROAD SPECTRUM

1. ALL types of epilepsy:
   • Generalized tonic-clonic seizures
   • Absence seizures - drug of choice (with ethosuximide)
   • Myoclonic seizures - drug of choice
   • Partial seizures
   • Juvenile myoclonic epilepsy - drug of choice
2. Bipolar disorder (Mood stabilizer) - especially acute mania and maintenance
3. Migraine prophylaxis - reduces frequency of attacks
4. Neuropathic pain (adjunct)
5. Status epilepticus (IV valproate - alternative to phenytoin)

Adverse Effects

1. Nausea, vomiting, GI upset - take with food; enteric-coated forms reduce this
2. Increased appetite and weight gain

Precautions

• Monitor LFTs before and during treatment (hepatotoxicity)
• Monitor CBC (thrombocytopenia)
• Avoid in liver disease
• Avoid/caution in women of childbearing age - prescribe folic acid 5 mg if essential
• Do NOT stop abruptly
• Watch for drug interactions (valproate inhibits CYP enzymes - raises levels of phenobarbitone, lamotrigine)

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Q3. Describe the management of Status Epilepticus. Discuss the drugs used and their rationale.

Status Epilepticus (SE)

Step-by-Step Management

• ABC (Airway, Breathing, Circulation)
• Oxygen, IV access, blood glucose
• Check glucose: If hypoglycemia → IV 50% dextrose

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"BZD is the FASTEST way to stop a seizure"

• Benzodiazepines enhance GABA activity at GABA-A receptors → open Cl- channels → hyperpolarize neurons → rapidly terminate seizures
• Work within 1-3 minutes
• Lorazepam preferred (longer duration of action 12-24 hrs vs. diazepam 20-30 min)
• Rectal diazepam (Diazepam rectal) - used in children, community settings when IV not available
• Midazolam IM/intranasal - if IV access not available (onset 5 min)

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• Blocks Na+ channels → prevents sustained repetitive firing
• Fosphenytoin is water-soluble prodrug of phenytoin - safer IV route (less cardiovascular toxicity, can give faster at 150 PE/min)
• Both require cardiac monitoring during infusion (hypotension, arrhythmias)
• Phenytoin: Give in SALINE only (precipitates in dextrose)

• IV Valproate 30 mg/kg - safe in children, no cardiovascular side effects, good for absence/myoclonic SE
• IV Levetiracetam - newer, well-tolerated, no cardiac monitoring needed

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• IV Phenobarbitone 20 mg/kg at 100 mg/min (effective but causes heavy sedation)
• IV Anaesthetic agents:
  • Propofol (drug of choice for refractory SE)
  • Thiopentone sodium (barbiturate anaesthetic)
  • Midazolam infusion
  • Ketamine (NMDA antagonist - increasing use)
• All require mechanical ventilation + EEG monitoring

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Q4. Classify antiepileptic drugs and discuss the pharmacological treatment of different types of epilepsy.

Pharmacological Treatment by Seizure Type

Memory aid: "Carbamazepine and Phenytoin are SODIUM channel blockers - NEVER use for myoclonic or absence seizures (they worsen these)." Valproate is SAFE for ALL types.

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UNIT II - OPIOID ANALGESICS

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Q5. Classify opioid analgesics. Describe Morphine - mechanism of action, pharmacological actions, therapeutic uses, adverse effects, contraindications, and toxicity.

Classification of Opioid Analgesics

• Natural: Morphine, Codeine (from opium poppy - Papaver somniferum)
• Semi-synthetic: Heroin (diacetylmorphine), Oxycodone, Hydromorphone, Buprenorphine, Nalbuphine
• Synthetic: Pethidine (Meperidine), Fentanyl, Methadone, Tramadol, Pentazocine

• Pure agonists: Morphine, Codeine, Pethidine, Fentanyl, Methadone, Tramadol
• Partial agonists: Buprenorphine (mu partial agonist)
• Mixed agonist-antagonists: Pentazocine, Nalbuphine, Butorphanol (kappa agonist + mu antagonist)
• Pure antagonists: Naloxone, Naltrexone, Methylnaltrexone

• Strong: Morphine, Fentanyl, Pethidine, Methadone
• Moderate: Codeine, Tramadol, Oxycodone
• Mild: Dextropropoxyphene

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MORPHINE (Prototype Opioid)

Mechanism of Action

Think: Morphine mimics the brain's own painkillers (endorphins)

• Activates opioid receptors (G-protein coupled receptors):
  • Mu (μ) receptors - mainly responsible for: analgesia, euphoria, respiratory depression, dependence, miosis, constipation, decreased GI motility
  • Kappa (κ) receptors - analgesia, sedation, dysphoria, miosis
  • Delta (δ) receptors - analgesia, mood modulation
• At receptor level (Gi-coupled):
  1. Reduces cAMP → reduced neuronal excitability
  2. Opens K+ channels → hyperpolarization → reduced firing
  3. Closes voltage-gated Ca2+ channels → reduced neurotransmitter release
• In pain pathways:
  • Spinal cord: Reduces substance P release → reduces pain transmission
  • Brain (periaqueductal gray, thalamus): Activates descending inhibitory pathways

Pharmacological Actions (System by System)

1. Analgesia - raises pain threshold; reduces pain perception and emotional response to pain. Works on both acute and chronic pain; visceral pain better than somatic pain.
2. Euphoria/Dysphoria - intense feeling of well-being → contributes to abuse
3. Sedation and drowsiness
4. Respiratory depression - reduces sensitivity of respiratory center to CO2 → MOST DANGEROUS effect; dose-dependent
5. Miosis (pin-point pupils) - stimulates Edinger-Westphal nucleus of oculomotor nerve; diagnostic sign of opioid toxicity; does NOT develop tolerance
6. Suppression of cough (antitussive) - acts on cough center in medulla
7. Nausea and vomiting - stimulates CTZ (chemoreceptor trigger zone)
8. Truncal rigidity at high doses (reduces cough in anesthesia)

Therapeutic Uses

1. Severe pain - post-operative pain, trauma, cancer pain (step 3 of WHO analgesic ladder), MI pain (IV morphine - reduces pain and anxiety)
2. Acute pulmonary edema - IV morphine relieves breathlessness by: vasodilation (reduces preload), sedation, analgesia (reduces anxiety)
3. Dyspnoea in terminal illness/cancer
4. Preanaesthetic medication - reduces anxiety, provides sedation
5. Cough suppression - codeine preferred (weaker opioid)
6. Diarrhea (codeine, loperamide preferred)
7. Balanced anesthesia (fentanyl preferred for intraoperative use)
8. Intrathecal/Epidural - post-operative analgesia with minimal systemic side effects

Adverse Effects

1. Nausea, vomiting (CTZ stimulation)
2. Constipation (most common; no tolerance develops)
3. Respiratory depression (dose-related; most dangerous)
4. Sedation, drowsiness, mental clouding
5. Urinary retention
6. Pruritus (histamine release; especially with IV/spinal morphine)
7. Miosis (pin-point pupils)
8. Tolerance (need increasing doses for same effect)
9. Physical and psychological dependence (addiction)
10. Withdrawal syndrome on abrupt discontinuation

Contraindications

1. Head injury, raised intracranial pressure (ICP) - CO2 retention from respiratory depression causes cerebral vasodilation → raises ICP further; also miosis masks neurological assessment
2. Bronchial asthma - bronchoconstriction (histamine release) + respiratory depression
3. Hypothyroidism (myxedema) - enhanced respiratory depression
4. Hepatic failure - reduced metabolism → accumulation
5. Renal failure - accumulation of active metabolite morphine-6-glucuronide
6. Acute pancreatitis, biliary colic - biliary spasm worsens pain
7. Labor - neonatal respiratory depression (use cautiously; have naloxone ready)
8. Pheochromocytoma - histamine-induced catecholamine release
9. Patients on MAO inhibitors (serotonin syndrome with pethidine; morphine also dangerous)

Toxicity (Opioid Overdose)

"Coma + Pin-point pupils (miosis) + Respiratory depression"

1. Airway, Breathing - secure airway, O2, assisted ventilation
2. Naloxone (Narcan) - specific antidote:
   • Pure opioid antagonist (competes at mu receptors)
   • IV 0.4-2 mg; repeat every 2-3 minutes (up to 10 mg)
   • Short half-life (30-90 min) → may need repeated doses or infusion (as morphine's half-life is longer)
   • Precipitates acute withdrawal in dependent patients
3. Gastric lavage (if oral ingestion, alert patient)
4. Supportive care

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Q6. Describe acute opioid poisoning. Discuss clinical features and management.

This is covered within Q5 (Toxicity section) above in detail. Expanded version:

Acute Opioid Poisoning

Clinical Features

1. Coma (deep unconsciousness, unresponsive to stimuli)
2. Pin-point pupils (miosis) - characteristic; bilateral; even in coma
3. Respiratory depression - slow, shallow, irregular breathing → apnea → death from respiratory failure

• Bradycardia, hypotension
• Hypothermia, cold clammy skin
• Cyanosis (lips, nail beds - due to hypoxia)
• Pulmonary edema (non-cardiogenic)
• Muscle flaccidity
• Urinary retention
• Decreased bowel sounds (GI depression)
• Death from respiratory failure + aspiration pneumonia

Management

• Open airway, position patient
• Oxygen via face mask (100%)
• IV access, monitor ECG, SpO2, BP

• IV Naloxone 0.4-2 mg (adult)
• Repeat every 2-3 minutes if no response (up to 10 mg total)
• Response: Pupil dilation, respiratory rate increases, consciousness returns (within 1-2 minutes)
• Infusion: Since naloxone half-life (30-90 min) << morphine half-life → give 2/3 of effective reversal dose as hourly infusion
• In neonatal opioid depression: Naloxone 0.01 mg/kg IV/IM
• Caution: Naloxone precipitates acute withdrawal in opioid-dependent patients (agitation, tachycardia, seizures, vomiting)

• Assisted ventilation (intubation if GCS <8 or SpO2 not maintained)
• IV fluids for hypotension
• Treat pulmonary edema (diuretics, positive pressure ventilation)
• Gastric lavage (if oral, conscious/intubated patient)
• Activated charcoal (if oral within 1 hour)
• Maintain body temperature (warming blankets)

• Continuous monitoring for 24 hours (risk of re-narcotization as naloxone wears off)

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Q7. Classify opioid antagonists and discuss their therapeutic uses.

Classification of Opioid Antagonists

• Naloxone (short-acting, IV/IM/nasal)
• Naltrexone (long-acting, oral)
• Nalmefene (long-acting, IV)

• Methylnaltrexone (Relistor) - SC/oral
• Naloxegol - oral
• Alvimopan - oral (GI only)

• Buprenorphine (mu partial agonist, kappa antagonist)
• Nalbuphine, Pentazocine (kappa agonists, mu antagonists)

Therapeutic Uses

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UNIT III - ANTIPSYCHOTIC DRUGS

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Q8. Classify antipsychotic drugs. Describe Chlorpromazine - mechanism of action, pharmacological actions, therapeutic uses, adverse effects, and precautions.

Classification of Antipsychotic Drugs

• Low potency: Chlorpromazine (CPZ), Thioridazine
• Medium potency: Trifluoperazine
• High potency: Fluphenazine, Perphenazine

• Clozapine (prototype - "gold standard" for refractory schizophrenia)
• Risperidone, Olanzapine, Quetiapine, Ziprasidone, Aripiprazole, Amisulpride, Paliperidone

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CHLORPROMAZINE (CPZ) - Prototype Typical Antipsychotic

Mechanism of Action

"CPZ is a DIRTY DRUG - it blocks everything!"

Pharmacological Actions

1. Antipsychotic: Reduces positive symptoms (hallucinations, delusions, thought disorder, agitation) in schizophrenia
2. Sedation (H1 blockade) - strong; not the same as sleep
3. Antiemetic (D2 blockade at CTZ)
4. Reduces body temperature (poikilothermia - body temp follows environment)
5. Catalepsy (waxy flexibility) at high doses
6. Does NOT cause analgesia but potentiates analgesics

Therapeutic Uses

1. Schizophrenia - reduces positive symptoms (hallucinations, delusions, agitation); less effective for negative symptoms
2. Acute mania (adjunct to lithium/valproate)
3. Antiemetic - drug/radiation-induced nausea; NOT motion sickness (requires anticholinergic)
4. Premedication before anesthesia - sedation, antiemetic, potentiates analgesia
5. Hiccups (intractable hiccups) - chlorpromazine specifically approved for this
6. Anxiety and agitation in psychotic patients
7. Potentiation of analgesics and anesthetics - reduces narcotic dose needed
8. Tetanus (muscle rigidity management - adjunct)
9. Hypothermia (induces deliberate hypothermia in surgery - "lytic cocktail")

Adverse Effects

Memory tip for EPR timing: "ADD To Tardive" = Acute dystonia → Akathisia → Drug-induced Parkinsonism → Tardive dyskinesia (chronological order)

• Sedation (strong with CPZ - low potency phenothiazines)
• Orthostatic hypotension (alpha blockade) - especially on first dose or IV use
• Anticholinergic effects - dry mouth, constipation, urinary retention, blurred vision, tachycardia
• Hyperprolactinaemia - galactorrhoea, amenorrhoea, gynecomastia
• Weight gain (H1 blockade + 5-HT blockade)
• Cholestatic jaundice (hypersensitivity reaction)
• Photosensitivity - sunburn; reddish-purple skin discolouration with chronic use
• Corneal and lens deposits (thioridazine → retinal pigmentation/pigmentary retinopathy; risk of blindness)
• Cardiac: QT prolongation (especially thioridazine → withdrawn for this)
• Neuroleptic Malignant Syndrome (NMS) - rare but life-threatening:
  • Features: Fever (hyperthermia >40°C), severe muscle rigidity, altered consciousness, autonomic instability (tachycardia, BP fluctuations)
  • Treatment: STOP antipsychotic, IV dantrolene (muscle relaxant), bromocriptine (D2 agonist), supportive care (cooling, IV fluids)
• Agranulocytosis - rare with typical; common with clozapine

Precautions

• Avoid IV injection rapidly (hypotension)
• Use with caution in epilepsy (lowers seizure threshold)
• Avoid in comatose patients or with CNS depressants (additive sedation)
• Caution in liver disease, BPH, glaucoma, cardiac disease
• Protect from sun (photosensitivity)
• Monitor blood count (rare agranulocytosis)
• Do not abruptly discontinue

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Q9. Classify atypical antipsychotic drugs. Discuss their advantages, therapeutic uses, and adverse effects.

Why "Atypical"?

1. Blocking 5-HT2A receptors in addition to D2 receptors (5-HT2A blockade partially reverses D2-related EPR and improves negative symptoms)
2. Fewer or no extrapyramidal side effects at therapeutic doses
3. Effective against BOTH positive AND negative symptoms
4. Less hyperprolactinaemia (except risperidone/paliperidone)

Advantages Over Typical Antipsychotics

Therapeutic Uses

1. Schizophrenia (first-line; most guidelines recommend atypicals as first choice)
2. Refractory schizophrenia - Clozapine (when 2+ antipsychotics fail)
3. Bipolar disorder - Olanzapine, Quetiapine (acute mania + maintenance)
4. Major depression with psychotic features - augmentation with Quetiapine, Aripiprazole
5. Autism - Risperidone, Aripiprazole (FDA approved for irritability in autism)
6. Tourette syndrome - Haloperidol, Pimozide
7. Dementia-related agitation (cautiously; increased mortality risk in elderly)
8. Borderline personality disorder (adjunct)

Adverse Effects of Atypical Antipsychotics

• Weight gain - olanzapine and clozapine cause the most weight gain
• Hyperglycaemia, diabetes mellitus (type 2)
• Dyslipidemia (raised triglycerides, reduced HDL)
• This metabolic syndrome increases cardiovascular risk significantly

• Agranulocytosis - 1-2% (potentially fatal); mandatory regular WBC monitoring (weekly for 6 months, then fortnightly)
• Seizures (lowers seizure threshold; dose-related)
• Hypersalivation (sialorrhoea) - paradoxical (M4 receptor agonism)
• Myocarditis, cardiomyopathy (rare but serious)
• Sedation, weight gain (extensive)

• Most likely atypical to cause EPR and hyperprolactinaemia (at higher doses)

• Cataracts (lens opacity) - annual slit lamp exam recommended
• Sedation, orthostatic hypotension

• QTc prolongation - avoid in cardiac patients

• Partial D2 agonist (unique); akathisia; nausea; weight-neutral

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Q10. Compare typical and atypical antipsychotic drugs.

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UNIT IV - ANTIDEPRESSANT DRUGS

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Q11. Classify antidepressant drugs. Discuss SSRIs - mechanism of action, therapeutic uses, adverse effects, and advantages over older antidepressants.

Classification of Antidepressants

• Tertiary amines: Amitriptyline, Imipramine, Clomipramine, Doxepin
• Secondary amines: Nortriptyline, Desipramine

• Irreversible non-selective: Phenelzine, Tranylcypromine, Isocarboxazid
• Reversible MAO-A selective (RIMA): Moclobemide

• NaSSA: Mirtazapine
• NDRI: Bupropion (Wellbutrin)
• SARI: Trazodone
• Melatonin agonist: Agomelatine
• SMS (Serotonin modulator and stimulator): Vortioxetine

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SELECTIVE SEROTONIN REUPTAKE INHIBITORS (SSRIs)

"SSRIs keep serotonin working longer in the synapse"

Mechanism of Action

• Normally after serotonin (5-HT) is released into the synapse, it is pumped back into the presynaptic neuron by the SERT (serotonin transporter) - a reuptake pump.
• SSRIs selectively block SERT → serotonin cannot be reuptaken → it accumulates in the synapse → prolonged activation of postsynaptic 5-HT receptors.
• Over 2-4 weeks of continuous therapy: Desensitization of presynaptic 5-HT1A autoreceptors occurs → further increases serotonin transmission.
• This explains the 2-4 week delay before therapeutic antidepressant effects appear (even though the reuptake is blocked from day 1).

Simple analogy: "SERT is a vacuum cleaner pulling serotonin back. SSRIs break the vacuum cleaner - serotonin stays in the synapse longer and does its job better."

Therapeutic Uses

1. Major depressive disorder (MDD) - FIRST-LINE (drug of choice for most patients)
2. Anxiety disorders:
   • Generalized anxiety disorder (GAD) - Escitalopram, Paroxetine
   • Panic disorder - Paroxetine, Fluoxetine, Sertraline
   • Social anxiety disorder - Sertraline, Paroxetine
   • OCD (Obsessive-Compulsive Disorder) - Fluoxetine, Sertraline, Fluvoxamine (DOC for OCD), Paroxetine
   • PTSD (Post-traumatic stress disorder) - Sertraline (FDA approved), Paroxetine
3. Bulimia nervosa - Fluoxetine (only FDA-approved for this)
4. Premenstrual dysphoric disorder (PMDD) - Fluoxetine, Sertraline
5. Premature ejaculation - Dapoxetine (short-acting SSRI specifically for this)
6. Neuropathic pain (adjunct)
7. Hot flushes in menopausal women (non-hormonal)

Adverse Effects

1. GI effects (most common, especially early):
   • Nausea, diarrhoea, vomiting, anorexia
   • Take after food; improves after 1-2 weeks
2. Sexual dysfunction - reduced libido, anorgasmia, delayed ejaculation (very common ~30-40%; most troublesome; persists)
3. Insomnia, agitation, restlessness (especially fluoxetine - most activating)
4. Headache
5. Weight changes - initial weight loss → long-term weight gain (paroxetine gains most weight)
6. Serotonin syndrome (when combined with other serotonergic drugs - MAOIs, tramadol, triptans):
   • Triad: Altered mental status + Autonomic instability (hyperthermia, tachycardia, sweating) + Neuromuscular abnormalities (tremor, clonus, hyperreflexia)
   • Treatment: STOP drug, cyproheptadine (5-HT antagonist), supportive care
7. Hyponatraemia (SIADH - inappropriate ADH secretion) - especially in elderly
8. Bleeding tendency - serotonin is required for platelet activation; SSRIs reduce platelet serotonin → increased bleeding risk; caution with NSAIDs/warfarin
9. QTc prolongation - Citalopram and Escitalopram at high doses
10. Suicidal ideation (Black box warning in <25 years, especially early treatment - first 1-2 weeks; monitor closely)
11. Discontinuation syndrome (abrupt withdrawal): Dizziness, sensory disturbances ("electric shocks/brain zaps"), irritability, nausea; especially with paroxetine (shortest half-life); Fluoxetine has least discontinuation syndrome (longest half-life ~4-6 days; self-tapering)

Advantages Over Older Antidepressants (TCAs and MAOIs)

Bottom line: SSRIs are the first-line choice because they are equally effective but FAR SAFER than TCAs and MAOIs.

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Q12. Classify atypical antidepressants and discuss their mechanism of action, therapeutic uses, and adverse effects.

Atypical Antidepressants

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1. Mirtazapine (NaSSA - Noradrenergic and Specific Serotonergic Antidepressant)

• Blocks alpha-2 adrenergic autoreceptors and heteroreceptors → removes the "brake" on norepinephrine and serotonin release → increases both NE and 5-HT in synapse.
• Blocks 5-HT2 and 5-HT3 receptors (but NOT 5-HT1A) → this is why it has no sexual dysfunction or GI side effects (unlike SSRIs).
• Blocks H1 histamine receptors → strong sedation.
• Does NOT inhibit reuptake.

• Depression, especially with:
  • Insomnia (uses sedation therapeutically; give at night)
  • Weight loss/anorexia (increases appetite)
  • Anxiety
  • Vomiting (5-HT3 blockade)
• Prevention of chemotherapy-induced nausea (5-HT3 blockade)

• Sedation (most common; due to H1 blockade; actually a benefit in insomnia)
• Weight gain and increased appetite (H1 blockade)
• Dry mouth (mild anticholinergic)
• NO sexual dysfunction
• NO GI side effects (5-HT3 blockade)
• Agranulocytosis (very rare)

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2. Bupropion (NDRI - Norepinephrine-Dopamine Reuptake Inhibitor)

• Blocks reuptake of norepinephrine AND dopamine (NOT serotonin).

• Major depression (comparable to SSRIs in efficacy)
• Smoking cessation (Zyban - reduces nicotine craving via dopamine pathways)
• ADHD (off-label; increases dopamine)
• Depression in patients with sexual dysfunction on SSRIs (bupropion has NO sexual side effects)
• Depression with weight gain concerns (weight-neutral to weight loss)

• Seizures (dose-related; lowers seizure threshold; contraindicated in epilepsy, bulimia nervosa, eating disorders)
• Insomnia, agitation, restlessness, headache
• Dry mouth
• NO sexual dysfunction
• NO weight gain (may cause weight loss)
• NO sedation

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3. Trazodone (SARI - Serotonin Antagonist and Reuptake Inhibitor)

• Inhibits serotonin reuptake + blocks 5-HT2A receptors and H1 receptors.

• Depression with insomnia (strong sedative - good for sleep)
• Often used at LOW doses for insomnia even in non-depressed patients
• Sexual dysfunction caused by SSRIs

• Sedation (major; useful in insomnia)
• Priapism (prolonged painful penile erection) - rare but characteristic; emergency urological condition
• Orthostatic hypotension
• Dry mouth

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4. Venlafaxine / Duloxetine (SNRI)

• Major depression
• GAD, panic disorder, social anxiety (venlafaxine, duloxetine)
• Neuropathic pain, fibromyalgia, diabetic neuropathy - duloxetine (FDA approved)
• Stress urinary incontinence - duloxetine
• Hot flushes in menopausal women

• Nausea, sweating, dry mouth, dizziness
• Hypertension (NE effect) - especially venlafaxine at high doses; monitor BP
• Sexual dysfunction (serotonergic)
• Discontinuation syndrome

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5. Agomelatine

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Q13. Write a detailed note on MAO Inhibitors - classification, mechanism of action, therapeutic uses, adverse effects, and drug interactions.

MAO Inhibitors (MAOIs)

"MAOIs boost monoamines by stopping their destruction"

• MAO-A - metabolizes norepinephrine, serotonin, tyramine (in gut/liver)
• MAO-B - metabolizes dopamine, phenylethylamine, tyramine

Classification

Mechanism of Action

• Inhibit MAO enzyme in nerve terminals → reduced breakdown of NE, 5-HT, dopamine → increased monoamine levels in synapse → antidepressant effect.
• Irreversible MAOIs: Form covalent bond with MAO → enzyme is permanently inactivated until new enzyme is synthesized (2+ weeks after stopping drug → reason for 2-week washout period before starting other drugs).
• Moclobemide (RIMA): Reversibly inhibits MAO-A; safer tyramine profile.
• Selegiline: At low doses, selectively inhibits MAO-B → used in Parkinson's disease (preserves dopamine); at high doses, also inhibits MAO-A → antidepressant use.

Therapeutic Uses

1. Treatment-resistant depression - when SSRIs/TCAs fail
2. Atypical depression (depression with: mood reactivity, weight gain, hypersomnia, leaden paralysis, interpersonal rejection sensitivity) - MAOIs may be superior
3. Panic disorder, social phobia (phenelzine)
4. Parkinson's disease - Selegiline + Rasagiline (MAO-B inhibitors; slow dopamine breakdown; neuroprotective)
5. Bulimia nervosa, PTSD (phenelzine; less commonly used)

Adverse Effects

1. Insomnia, agitation
2. Orthostatic hypotension (most common)
3. Weight gain
4. Sexual dysfunction
5. Peripheral neuropathy (pyridoxine deficiency - phenelzine; treat with B6)

This is the most important MAOI adverse effect in exams!

• Normally, dietary tyramine (in aged cheese, red wine, cured meats, fermented foods) is metabolized by MAO-A in the gut wall and liver before reaching systemic circulation.
• MAOIs block this first-pass metabolism → tyramine enters systemic circulation → displaces NE from nerve terminals → massive NE release → severe, potentially fatal hypertensive crisis.
• Features: Severe pounding headache, palpitations, flushing, neck stiffness, hypertension (BP can reach >200/120), intracranial haemorrhage, death.
• Treatment: IV Phentolamine (alpha-blocker) or IV Nifedipine/Labetalol.
• Prevention: Strict low-tyramine diet while on MAOIs (and 2 weeks after stopping).

Drug Interactions (Potentially Fatal)

Washout rules: Stop MAOI → wait 14 days before starting SSRI. Stop fluoxetine (long half-life) → wait 5 WEEKS before starting MAOI.

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Q14. Compare Tricyclic Antidepressants (TCAs) and SSRIs.

Bottom line: TCAs and SSRIs are equally effective for depression but SSRIs win on SAFETY, TOLERABILITY, and BREADTH of use.

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UNIT V - MOOD STABILIZERS

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Q15. Describe Lithium - mechanism of action, pharmacological effects, therapeutic uses, adverse effects, toxicity, monitoring, and management of toxicity.

LITHIUM (Prototype Mood Stabilizer)

"Lithium is the gold standard for Bipolar Disorder - but it's a double-edged sword: incredibly effective but needs careful monitoring"

Mechanism of Action

1. Inositol Depletion Hypothesis (Most Important):
   • Lithium inhibits inositol monophosphatase and inositol polyphosphate 1-phosphatase enzymes.
   • These enzymes are needed to recycle inositol (for the phosphatidylinositol second messenger system - IP3/DAG pathway).
   • Lithium blocks inositol recycling → depletes free inositol → reduces IP3/DAG signaling → dampens overactive neuronal transmission in mania.
   • This effect is "use-dependent" - affects most those neurons firing most rapidly (like in mania).
2. Protein Kinase C (PKC) inhibition - reduces neuronal excitability
3. GSK-3β (Glycogen Synthase Kinase-3β) inhibition - neuroprotective; mood-stabilizing
4. Increases serotonin synthesis and release - contributes to antidepressant effect
5. Mimics Na+ in some cells (similar ionic radius) → alters Na+/K+ transport → reduces neuronal hyperexcitability

Pharmacological Effects

• Antimanic - reduces symptoms of mania in 7-14 days
• Antidepressant - prevents depressive episodes (less effective for acute depression)
• Mood stabilizer - prevents BOTH manic and depressive recurrences in bipolar disorder
• Anti-suicidal - reduces suicidal behavior in bipolar and major depression
• No sedation, no tolerance, no dependence

Therapeutic Uses

1. Acute mania - treats current manic episode (onset 7-14 days; antipsychotics/BZD used for rapid control meanwhile)
2. Maintenance/Prophylaxis in Bipolar Disorder (Type I & II) - drug of choice; prevents recurrences of BOTH mania and depression
3. Augmentation in treatment-resistant depression (add to antidepressant)
4. Cluster headache prophylaxis
5. Neutropenia - lithium stimulates granulopoiesis (increases WBC count)
6. SIADH - causes nephrogenic diabetes insipidus → reduces free water retention

Adverse Effects

1. Fine tremor of hands (most common; dose-related; treat with propranolol)
2. Polyuria and polydipsia (nephrogenic diabetes insipidus - reduces renal response to ADH)
3. Weight gain (increased appetite)
4. Nausea, vomiting, diarrhea (take with food)
5. Hypothyroidism (common with long-term use - lithium inhibits thyroid hormone synthesis and release); check TFTs regularly; treat with levothyroxine if needed
6. Goitre (due to compensatory TSH rise)
7. Acne, psoriasis exacerbation
8. Hair loss (alopecia)
9. Metallic taste in mouth
10. Oedema (ankle)
11. Cognitive dulling (memory issues - "cognitive blunting")
12. Leukocytosis (mild; benign - WBC 10,000-14,000)

• Ebstein's anomaly (downward displacement of tricuspid valve) - cardiac malformation; Category D in first trimester

Lithium Toxicity

"Lithium is a drug with one of the narrowest therapeutic windows in medicine"

• Dehydration (vomiting, diarrhea, exercise, hot weather) → reduced renal blood flow → increased Li reabsorption
• Salt restriction (Na+ depletion → kidneys compensate by reabsorbing more Na+/Li+)
• NSAIDs (reduce GFR, increase Li retention - most common drug interaction)
• Thiazide diuretics (reduce NaCl reabsorption → kidneys reabsorb more Li+; can raise levels by 50%)
• ACE inhibitors, ARBs (reduce renal clearance of Li)
• Loop diuretics (less dangerous; Na+ loss doesn't proportionally increase Li+ retention as much)

Monitoring of Lithium

Management of Lithium Toxicity

1. STOP lithium immediately
2. IV fluids (Normal saline) - rapidly rehydrate; saline loading promotes lithium excretion
3. NO thiazides (worsen lithium retention)
4. Hemodialysis - definitive treatment for severe toxicity (Li >2.5 mEq/L, seizures, coma, renal failure); Li is dialyzable
5. Supportive: Anticonvulsants for seizures, cardiac monitoring
6. Sodium polystyrene sulphonate - cation exchange resin (sometimes used to bind lithium in gut if oral)
7. Monitor serum lithium levels every 4-6 hours until safe

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Q16. Classify drugs used in Bipolar Disorder and discuss their therapeutic role.

Classification of Drugs Used in Bipolar Disorder

• Lithium (gold standard)
• Sodium Valproate (Valproic acid)
• Carbamazepine / Oxcarbazepine

• Olanzapine, Quetiapine, Risperidone, Aripiprazole, Ziprasidone, Asenapine, Lurasidone

• Lorazepam, Clonazepam (rapid control of agitation)

Therapeutic Role

• First-line: Lithium OR Valproate OR atypical antipsychotic (Olanzapine, Quetiapine, Risperidone)
• Add benzodiazepine (lorazepam) for immediate sedation/agitation control
• Valproate preferred over lithium when: rapid cycling, mixed episodes, substance use comorbidity
• Carbamazepine: Alternative when lithium+valproate fail

• Quetiapine (FDA approved) - most evidence
• Lamotrigine - effective for bipolar depression; mood stabilizer
• Lurasidone (with lithium or valproate)
• Note: Antidepressants ALONE are controversial (may trigger manic switch); use only with a mood stabilizer

• Lithium - reduces both manic AND depressive recurrences; also reduces suicide risk
• Valproate - better for rapid cycling bipolar (4+ mood episodes/year)
• Lamotrigine - better for preventing depressive episodes
• Olanzapine, Quetiapine, Aripiprazole - maintenance atypical antipsychotics

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UNIT VI - ANXIOLYTICS AND SEDATIVE-HYPNOTICS

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Q17. Classify antianxiety drugs. Describe Benzodiazepines - mechanism of action, pharmacological actions, therapeutic uses, adverse effects, and precautions.

Classification of Antianxiety Drugs

• Short-acting: Triazolam, Midazolam, Alprazolam (short-to-intermediate)
• Intermediate-acting: Temazepam, Lorazepam, Oxazepam
• Long-acting: Diazepam, Clonazepam, Chlordiazepoxide

• SSRIs: Escitalopram, Paroxetine, Sertraline
• SNRIs: Venlafaxine, Duloxetine
• TCAs: Imipramine (panic disorder)

• Hydroxyzine (Atarax) - acute anxiety; no dependence

• Propranolol (situational anxiety - performance anxiety, stage fright - reduces palpitations/tremor)

• Phenobarbitone, Pentobarbitone, Thiopentone (now mainly for epilepsy/anaesthesia)

• Pregabalin/Gabapentin (GABAergic; for GAD)
• Meprobamate (obsolete)
• Chloral hydrate (obsolete hypnotic)

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BENZODIAZEPINES (BZDs)

"BZDs make GABA work better - like adding a power booster to the brain's brake system"

Mechanism of Action

• GABA-A receptor is the main inhibitory neurotransmitter receptor in the brain. It is a ligand-gated Cl- ion channel.
• GABA-A receptor has binding sites for: GABA itself, benzodiazepines, barbiturates, neurosteroids, ethanol, picrotoxin.
• BZDs bind to a specific allosteric site (between alpha and gamma subunits) on the GABA-A receptor - the BZD recognition site.
• When GABA binds its site AND a BZD also binds its site: BZD increases the FREQUENCY of Cl- channel opening (in response to GABA) → more Cl- enters → hyperpolarization → reduced neuronal excitability.

Important distinction:

• BZDs: increase FREQUENCY of Cl- channel opening (need GABA to be present)
• Barbiturates: increase DURATION of Cl- channel opening (can act without GABA at high doses)
• BZDs do NOT replace GABA - they enhance its effect (modulatory)
• This is why BZDs are SAFER than barbiturates - they have a "ceiling effect" and require GABA

Pharmacological Actions

1. Anxiolytic (anti-anxiety) - reduces subjective anxiety; limbic system (amygdala, hippocampus)
2. Sedation - drowsiness; reduces alertness; dose-dependent
3. Hypnotic (sleep) - larger doses; reduce sleep latency, reduce REM sleep (may cause vivid dreams/nightmares on withdrawal), increase stage 2 NREM sleep
4. Anticonvulsant/Anti-epileptic - clonazepam, diazepam; effective for all seizure types; IV diazepam/lorazepam = first-line for status epilepticus
5. Muscle relaxant (central) - diazepam; reduces spasticity by acting on interneurons in spinal cord; useful in muscle spasm, tetanus
6. Anterograde amnesia - inability to form new memories during drug action; useful for pre-procedure sedation (endoscopy), also misuse potential (date rape drug)
7. No analgesia - BZDs do NOT relieve pain directly; may reduce anxiety component of pain
8. Minimal cardiovascular/respiratory depression at therapeutic doses (advantage over barbiturates)

Therapeutic Uses

1. Anxiety disorders - GAD (short-term), panic disorder, social anxiety (clonazepam, alprazolam)
2. Insomnia - short-term (nitrazepam, temazepam, triazolam, midazolam); NOT recommended long-term (dependence)
3. Epilepsy:
   • Status epilepticus (IV diazepam, lorazepam) - first-line
   • Chronic epilepsy (clonazepam) - myoclonic, absence
   • Febrile convulsions (rectal diazepam)
4. Acute alcohol withdrawal - chlordiazepoxide or diazepam (prevent DTs and withdrawal seizures)
5. Muscle relaxation - diazepam for muscle spasm, spasticity, tetanus, back pain
6. Pre-operative sedation / premedication - midazolam (anterograde amnesia, sedation, anxiolysis)
7. Procedural sedation - IV midazolam (endoscopy, dental procedures)
8. Acute mania (adjunct with mood stabilizer for rapid sedation)
9. Night terrors, sleepwalking - clonazepam
10. Restless legs syndrome - clonazepam

Adverse Effects

1. Sedation, drowsiness (most common) - impairs driving, operating machinery
2. Anterograde amnesia - cannot form new memories after taking drug
3. Ataxia, coordination problems (especially elderly - falls)
4. Respiratory depression - at high doses, especially with alcohol or opioids; less than barbiturates
5. Tolerance - develops to sedative and hypnotic effects (less to anxiolytic); need increasing doses
6. Physical and psychological dependence - major problem with long-term use; develops even at therapeutic doses after 2-4 weeks
7. Withdrawal syndrome (on abrupt discontinuation after regular use):
   • Features: Rebound anxiety (worse than before), insomnia, tremor, sweating, tachycardia, seizures (severe cases), confusion
   • Always taper gradually when stopping
8. Paradoxical reactions - excitement, aggression, hostility (rare; especially in elderly/children)
9. Hangover effect - residual sedation next morning (long-acting BZDs)

• Relatively SAFE alone - causes sedation, ataxia, slurred speech, but rarely fatal alone
• Combined with alcohol/opioids = DANGEROUS respiratory depression
• Antidote: Flumazenil (competitive BZD antagonist at GABA-A receptor) - IV 0.2 mg; short half-life (reversal may not last) - repeat doses needed

Precautions

• Short-term use only (2-4 weeks for anxiety/insomnia)
• Gradual dose tapering to avoid withdrawal
• Avoid in: Respiratory disease (COPD, sleep apnoea), liver failure, elderly (half-life prolonged → falls), pregnancy (category D - neonatal floppy infant syndrome)
• Avoid combination with alcohol, opioids, CNS depressants
• LOT preferred in elderly: Lorazepam, Oxazepam, Temazepam (no active metabolites; shorter half-life; safer in liver disease)
• Addictive potential - schedule H/H1 drug

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Q18. Compare Benzodiazepines and Barbiturates.

Key memory point: Barbiturates killed patients in overdose (small margin between sedative and lethal dose). BZDs replaced them for anxiety/insomnia because BZDs are much SAFER.

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Q19. Compare Benzodiazepines and Buspirone in the treatment of anxiety disorders.

Buspirone

• Activates 5-HT1A autoreceptors (presynaptically) → reduces serotonin release → anxiolytic effect
• Also has weak D2 antagonist properties
• Does NOT interact with GABA-A receptors (completely different mechanism from BZDs)

Clinical Bottom Line

"Use BZDs for IMMEDIATE relief; use Buspirone for LONG-TERM anxiety management without dependence"

• BZDs are ideal when you need rapid control (acute panic attack, procedural anxiety, short-term situational anxiety).
• Buspirone is ideal for chronic GAD where long-term daily therapy is needed and addiction/dependence is a concern.
• SSRIs/SNRIs are now actually the first-line for most chronic anxiety disorders (buspirone and BZDs are second-line).

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EXAM TIPS SUMMARY