Unit III: Describe drugs acting on gastro-intestinal system & nurse's responsibilities · Drugs acting on G.I. system · Pharmacology of commonly used drugs · Emetics and Antiemetics · Laxatives and Purgatives · Antacids and antipeptic ulcer drugs · Anti-diarrheals – Fluid and electrolyte therapy, Furazolidone, dicyclomine · Composition, action, dosage, route, indications, contraindications, drug interactions, side effects, adverse effects, toxicity and role of nurse Ish topic say meri kl paper hone wali hai so mujhe ye topic puri yad krayo
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I have comprehensive content from Katzung's pharmacology on all GI drug classes. Now I have enough to write a thorough study guide. Let me compile the complete notes.
🏥 Unit III: Drugs Acting on the Gastrointestinal System
Complete Study Notes for Nursing Pharmacology Exam
📌 OVERVIEW — GI Drug Classification
| Category | Purpose |
|---|---|
| Emetics | Induce vomiting |
| Antiemetics | Prevent/treat nausea & vomiting |
| Laxatives & Purgatives | Facilitate bowel movement |
| Antacids & Anti-peptic ulcer drugs | Reduce gastric acid, heal ulcers |
| Anti-diarrheals | Reduce frequency of loose stools |
| Fluid & Electrolyte Therapy | Replace losses in diarrhea |
1️⃣ EMETICS (Vomiting-Inducing Drugs)
Definition
Emetics are drugs that induce vomiting. Used mainly in poisoning management (though their use has declined with modern toxicology).
🔑 Ipecac Syrup (Most important emetic)
| Feature | Detail |
|---|---|
| Composition | Contains emetine + cephaeline (alkaloids from Cephaelis ipecacuanha plant) |
| Route | Oral |
| Adult Dose | 15–30 mL followed by 200–300 mL water |
| Paediatric Dose | 10–15 mL |
Mechanism of Action:
- Peripheral: Irritates gastric mucosa → triggers vomiting reflex
- Central: Stimulates the Chemoreceptor Trigger Zone (CTZ) in the medulla → activates vomiting center
Indications:
- Accidental oral poisoning (alert patient)
- Drug overdose (within 30–60 minutes of ingestion)
Contraindications:
- Corrosive/caustic substance ingestion (acids, alkalis) — re-exposure to esophagus causes more damage
- Petroleum products (risk of aspiration pneumonia)
- Unconscious/drowsy patients
- Infants < 6 months
- Convulsions or cardiac arrhythmias
- Antiemetics already given
Adverse Effects / Toxicity:
- Prolonged vomiting, diarrhea
- Muscle weakness, hypotension (with overdose)
- Emetine cardiotoxicity — arrhythmias with excessive use
- Aspiration of vomitus
🔑 Apomorphine (Centrally Acting Emetic)
| Feature | Detail |
|---|---|
| Mechanism | Dopamine D2 agonist → directly stimulates CTZ |
| Route | Subcutaneous injection |
| Onset | 5–10 minutes |
Contraindications: Respiratory depression, CNS depression, corrosives ingested
👩⚕️ Nurse's Responsibilities for Emetics
- Assess — Is the patient conscious? Gag reflex intact?
- Do NOT give if patient ingested corrosives, oils, or is unconscious
- Position — Keep patient upright/leaning forward to prevent aspiration
- Have suction ready to clear airway
- Document — Time of ingestion, substance taken, time emetic given, amount vomited
- Monitor vital signs — Especially pulse and BP (emetine cardiotoxicity risk)
- Inform physician immediately after administration
- Activated charcoal may be given after vomiting subsides (as per protocol)
2️⃣ ANTIEMETICS (Anti-vomiting Drugs)
Physiology of Vomiting (Quick Recap)
The vomiting center (medulla oblongata) receives input from:
- CTZ (Chemoreceptor Trigger Zone) — rich in D2 dopamine receptors, opioid receptors, 5-HT3 receptors
- Vestibular system (CN VIII) — M2 muscarinic + H1 histamine receptors (→ motion sickness)
- Vagal afferents from gut — 5-HT3 receptors (triggered by chemo, radiation, infection)
- CNS/Cortex — Psychological causes, anticipatory vomiting
🔑 CLASS A: Serotonin 5-HT3 Antagonists ("Setrons")
| Drug | Dose | Route |
|---|---|---|
| Ondansetron | 4–8 mg | Oral / IV |
| Granisetron | 1 mg | Oral / IV / Transdermal patch |
| Dolasetron | 100 mg | Oral / IV |
| Palonosetron | 0.25 mg IV | IV (half-life 40 hours — best for delayed nausea) |
Mechanism: Block 5-HT3 receptors on vagal afferents in gut AND in CTZ → prevent vomiting signal to brain
Indications:
- Chemotherapy-induced nausea & vomiting (CINV) — First-line!
- Radiation-induced nausea
- Post-operative nausea & vomiting (PONV)
- Ondansetron: also used in pregnancy nausea
Contraindications: Hypersensitivity, prolonged QT interval (serotonin antagonists can prolong QT)
Drug Interactions:
- Drugs that prolong QT interval (antiarrhythmics, some antibiotics)
- CYP450 enzyme inducers/inhibitors may alter metabolism
Adverse Effects:
- Headache, constipation, diarrhea
- Dizziness, fatigue
- Prolonged QT interval (especially dolasetron)
🔑 CLASS B: Dopamine D2 Antagonists
Metoclopramide (Reglan)
| Feature | Detail |
|---|---|
| Mechanism | Blocks D2 receptors in CTZ + enhances gastric motility (prokinetic) |
| Dose | 10 mg oral/IV/IM |
| Route | Oral, IV, IM |
| Indications | CINV, GERD, diabetic gastroparesis, post-op nausea |
Contraindications: GI obstruction, Parkinson's disease, pheochromocytoma, epilepsy
Adverse Effects:
- Extrapyramidal symptoms (EPS) — tardive dyskinesia, akathisia (with long-term use)
- Sedation, restlessness
- Galactorrhea (increased prolactin)
- Diarrhea
Domperidone (Motilium)
- Similar to metoclopramide but does NOT cross BBB → fewer EPS
- Used for gastroparesis, nausea from Parkinson's medications
- Adverse effect: QT prolongation, cardiac arrhythmias
🔑 CLASS C: Antihistamines (H1 blockers)
| Drug | Dose | Indications |
|---|---|---|
| Promethazine | 12.5–25 mg | Motion sickness, PONV, pregnancy |
| Dimenhydrinate | 50–100 mg | Motion sickness |
| Meclizine | 25–50 mg | Motion sickness, vertigo |
| Diphenhydramine | 25–50 mg | Motion sickness, PONV |
Mechanism: Block H1 receptors in vestibular system + CNS → reduce motion-triggered vomiting
Adverse Effects: Sedation, dry mouth, blurred vision, urinary retention (anticholinergic)
🔑 CLASS D: Anticholinergics
| Drug | Detail |
|---|---|
| Scopolamine (Hyoscine) | Transdermal patch behind ear; best for motion sickness; acts on M2 receptors in vestibular system |
| Onset | 4 hours before travel |
Adverse Effects: Dry mouth, drowsiness, blurred vision, urinary retention
🔑 CLASS E: Corticosteroids
| Drug | Use |
|---|---|
| Dexamethasone | Used with 5-HT3 antagonists for CINV; mechanism unclear but very effective |
🔑 CLASS F: NK1 Receptor Antagonists (Neurokinin-1)
| Drug | Dose | Use |
|---|---|---|
| Aprepitant | 125 mg Day 1, then 80 mg Days 2–3 | Prevention of delayed CINV |
| Fosaprepitant | 150 mg IV | Same as above (IV prodrug) |
Mechanism: Block NK1 (substance P) receptors in brain → block vomiting center
Drug Interaction: Inhibits CYP3A4 → increases levels of many drugs including dexamethasone (dose reduction needed)
👩⚕️ Nurse's Responsibilities for Antiemetics
- Assess cause of nausea (chemo? motion? PONV?) → guides drug selection
- Administer prophylactically before chemotherapy (30 min IV before chemo)
- Monitor for EPS with metoclopramide — especially in young patients
- Monitor ECG for QT prolongation (ondansetron, domperidone)
- IV hydration — nauseous patients may be dehydrated; maintain IV access
- Dietary guidance — small, frequent meals; avoid strong smells
- Positioning — semi-Fowler's position (head elevated 30–45°)
- Safety — antihistamines/anticholinergics cause drowsiness → fall precautions
- Document — frequency, nature, volume of vomiting
3️⃣ LAXATIVES AND PURGATIVES
Definition
- Laxative: Mild drug producing soft, formed stool — for constipation
- Purgative/Cathartic: Stronger action producing watery, rapid evacuation — pre-surgical/procedure bowel prep
Classification
| Class | Examples | Mechanism |
|---|---|---|
| Bulk-forming | Psyllium, Methylcellulose, Ispaghula husk | Absorb water → increase stool bulk → stimulate peristalsis |
| Osmotic/Saline | Lactulose, Sorbitol, MgSO4 (Epsom salt), Mg hydroxide (Milk of Magnesia) | Retain water in bowel by osmosis → increase stool fluidity |
| Stimulant/Irritant | Senna, Bisacodyl, Castor oil, Phenolphthalein | Irritate intestinal mucosa & stimulate myenteric plexus → increased peristalsis |
| Emollient/Stool softeners | Docusate (Colace) | Surfactant action → water penetrates stool → softens it |
| Lubricant | Liquid paraffin (Mineral oil) | Coats stool surface → reduces friction → easier passage |
🔑 Key Drugs in Detail
Lactulose (Osmotic)
| Feature | Detail |
|---|---|
| Composition | Synthetic disaccharide (not absorbed) |
| Dose | 15–30 mL (10–20 g) orally, 1–3 times/day |
| Route | Oral |
| Mechanism | Not digested; bacteria ferment → produces organic acids → lowers colonic pH + osmotic effect → draws water into colon → soft stool |
| Special Use | Hepatic encephalopathy — reduces ammonia absorption from gut |
| Onset | 24–48 hours |
Adverse Effects: Flatulence, cramping, diarrhea (with excess)
Bisacodyl (Stimulant Laxative)
| Feature | Detail |
|---|---|
| Dose | 5–10 mg oral at bedtime; 10 mg rectal suppository |
| Route | Oral, rectal |
| Mechanism | Stimulates myenteric plexus + inhibits NaCl absorption in colon |
| Onset | Oral: 6–12 hours; Rectal: 15–60 minutes |
| Indication | Short-term constipation, bowel prep before procedures |
Adverse Effects: Abdominal cramps, diarrhea
⚠️ Do not crush enteric-coated tablets (causes gastric irritation)
Senna (Stimulant — Herbal)
| Feature | Detail |
|---|---|
| Source | Cassia senna pods/leaves |
| Dose | 15–30 mg sennosides at bedtime |
| Mechanism | Anthraquinone glycosides → converted by colonic bacteria → stimulate peristalsis |
| Onset | 6–12 hours |
| Adverse Effects | Cramping, melanosis coli (long-term), electrolyte loss |
Castor Oil (Stimulant Purgative)
| Feature | Detail |
|---|---|
| Mechanism | Hydrolyzed in gut to ricinoleic acid → stimulates small intestine + inhibits water absorption |
| Dose | 15–60 mL oral |
| Onset | 2–6 hours (fast — used for bowel prep) |
| Adverse Effects | Severe cramps, complete evacuation, dehydration |
Liquid Paraffin (Mineral Oil — Lubricant)
- Mechanism: Lubricates stool surface; softens stool
- Adverse Effects: Malabsorption of fat-soluble vitamins (A, D, E, K), lipid pneumonia if aspirated (avoid in elderly)
- Contraindication: Elderly, dysphagia patients
Magnesium Sulfate / Magnesium Hydroxide (Saline Purgative)
- Mechanism: Osmotic — retains water in bowel
- Dose: MgSO4: 5–15 g in water; Milk of Magnesia: 30–60 mL
- Contraindication: Renal failure (Mg2+ accumulates → toxicity)
👩⚕️ Nurse's Responsibilities for Laxatives
- Assess bowel pattern before giving — rule out bowel obstruction (laxatives are contraindicated in obstruction)
- Adequate fluid intake with bulk-forming agents — must take with plenty of water (risk of intestinal obstruction if insufficient fluid)
- Do NOT give bisacodyl within 1 hour of milk or antacids (enteric coating dissolves prematurely)
- Avoid long-term use of stimulant laxatives — leads to laxative dependence, melanosis coli
- Liquid paraffin — never give to bedridden/elderly patients due to aspiration risk
- Lactulose in hepatic encephalopathy — monitor ammonia levels, stool frequency (target 2–3 soft stools/day)
- Monitor electrolytes with prolonged use (K+ loss)
- Rectal suppositories — educate patient on correct insertion technique (pointed end first, left lateral position)
- Document — bowel movements, stool consistency, any adverse effects
4️⃣ ANTACIDS AND ANTI-PEPTIC ULCER DRUGS
Physiology (Quick Recap)
Parietal cells have 3 receptors: H2 (histamine), M3 (acetylcholine), CCK-B (gastrin)
→ All activate H+/K+-ATPase (proton pump) → acid secretion
Anti-ulcer drugs target these receptors or neutralize the acid.
🔑 CLASS A: Antacids (Neutralize existing acid)
| Drug | Composition | Special Notes |
|---|---|---|
| Aluminum hydroxide | Al(OH)3 | Causes constipation; binds phosphate (used in renal failure) |
| Magnesium hydroxide | Mg(OH)2 | Causes diarrhea |
| Combination | Al(OH)3 + Mg(OH)2 (Gelusil, Maalox) | Balanced bowel effect |
| Calcium carbonate | CaCO3 | Fast-acting; rebound acid secretion; risk of hypercalcemia |
| Sodium bicarbonate | NaHCO3 | Fast but CO2 causes belching; Na load → avoid in hypertension |
Mechanism: Neutralize gastric HCl → raise gastric pH → inactivate pepsin (inactive above pH 4)
Dose: 15–30 mL liquid or 1–2 tablets, 1–2 hours after meals and at bedtime
Drug Interactions:
- Antacids reduce absorption of tetracyclines, fluoroquinolones, iron, digoxin, ketoconazole — give at least 2 hours apart
- Alter urinary pH → affect renal excretion of other drugs
Adverse Effects:
- Al(OH)3: Constipation, phosphate depletion
- Mg(OH)2: Diarrhea, hypermagnesemia in renal failure
- CaCO3: Milk-alkali syndrome (hypercalcemia + alkalosis)
🔑 CLASS B: H2 Receptor Blockers (Histamine Antagonists)
| Drug | Dose | Route |
|---|---|---|
| Cimetidine | 300 mg QID or 800 mg at night | Oral / IV |
| Ranitidine | 150 mg BD or 300 mg at night | Oral / IV (withdrawn in many countries due to NDMA concerns) |
| Famotidine | 20 mg BD or 40 mg at night | Oral / IV |
| Nizatidine | 150 mg BD or 300 mg at night | Oral |
Mechanism: Competitively block H2 receptors on parietal cells → reduce histamine-stimulated acid secretion by ~70%
Indications: Peptic ulcer (gastric/duodenal), GERD, Zollinger-Ellison syndrome, stress ulcer prophylaxis
Drug Interactions (Cimetidine is the worst offender!):
- Cimetidine inhibits CYP450 enzymes → increases blood levels of: warfarin, phenytoin, theophylline, lidocaine
- Reduces absorption when given with antacids (give 1 hour apart)
Adverse Effects:
- Cimetidine: Gynecomastia, impotence, confusion (in elderly), drug interactions
- All H2 blockers: headache, diarrhea, constipation, dizziness
- Rare: thrombocytopenia, elevated liver enzymes
🔑 CLASS C: Proton Pump Inhibitors (PPIs) — Most Potent Acid Suppressors
| Drug | Dose | Route |
|---|---|---|
| Omeprazole | 20–40 mg once daily | Oral / IV |
| Esomeprazole | 20–40 mg once daily | Oral / IV |
| Lansoprazole | 15–30 mg once daily | Oral / IV |
| Pantoprazole | 40 mg once daily | Oral / IV |
| Rabeprazole | 20 mg once daily | Oral |
Mechanism:
- PPIs are prodrugs — activated in the acidic parietal cell canaliculus
- Activated form irreversibly inhibits H+/K+-ATPase (proton pump) → >90% reduction in acid secretion
- Longest-lasting acid suppression (once daily dosing sufficient)
Indications:
- Peptic ulcer disease (especially H. pylori eradication regimens)
- GERD, erosive esophagitis
- Zollinger-Ellison syndrome
- NSAID-induced ulcers (prophylaxis + treatment)
- Stress ulcer prophylaxis in ICU
H. pylori Eradication "Triple Therapy":
PPI + Amoxicillin + Clarithromycin for 14 days ✔️
Contraindications: Hypersensitivity
Drug Interactions:
- Reduce absorption of ketoconazole, itraconazole, atazanavir (pH-dependent)
- Omeprazole/Esomeprazole: Inhibit CYP2C19 → reduce clopidogrel activation (increased bleeding risk)
Adverse Effects (short-term):
- Headache, nausea, diarrhea, constipation, abdominal pain
Adverse Effects (long-term use):
- Hypomagnesemia (serious — monitor Mg2+)
- Vitamin B12 deficiency (reduced acid → impaired B12 absorption)
- C. difficile infection (↑ risk with reduced gastric acidity)
- Osteoporosis / fractures (reduced calcium absorption)
- Increased risk of community-acquired pneumonia
🔑 CLASS D: Mucosal Protective Agents
Sucralfate
| Feature | Detail |
|---|---|
| Composition | Aluminum salt of sulfated sucrose |
| Mechanism | In acidic pH, forms viscous gel that coats ulcer base → physical barrier; also stimulates prostaglandin synthesis |
| Dose | 1 g QID (30 minutes before meals + at bedtime) |
| Route | Oral |
| Important | Does NOT neutralize acid; works best at low pH (give before food, not with antacids) |
Drug Interactions: Reduces absorption of fluoroquinolones, phenytoin, digoxin (give 2 hours apart)
Adverse Effects: Constipation (aluminum content), dry mouth
Misoprostol (Prostaglandin E1 analog)
| Feature | Detail |
|---|---|
| Mechanism | Stimulates mucus & bicarbonate secretion + enhances mucosal blood flow + inhibits acid secretion |
| Dose | 200 mcg QID with food |
| Indication | Prevention of NSAID-induced ulcers |
Contraindication: PREGNANCY — causes uterine contractions → abortion
Adverse Effects: Diarrhea, cramping (most common), nausea
Bismuth Subsalicylate (Pepto-Bismol)
- Antimicrobial against H. pylori
- Protective coating on mucosa
- Used in H. pylori quadruple therapy
- Adverse Effect: Black stools/tongue (harmless), tinnitus with excess
👩⚕️ Nurse's Responsibilities for Antacids & Anti-Ulcer Drugs
- Timing matters:
- Antacids: 1–2 hours after meals and at bedtime
- Sucralfate: 30 minutes before meals on empty stomach
- PPIs: 30–60 minutes before morning meal (taken on empty stomach for best activation)
- Drug interactions — space antacids and other oral drugs by at least 2 hours
- Avoid NSAIDs, alcohol, smoking, spicy food — aggravate ulcers
- H. pylori triple therapy — stress importance of completing full 14-day course (compliance critical)
- Monitor for signs of GI bleeding — black/tarry stools (melena), hematemesis
- Long-term PPI patients — monitor Mg2+, B12, bone density
- Misoprostol — ensure female patients are NOT pregnant; counsel about contraception
- Cimetidine — monitor drug levels of co-prescribed medications (warfarin, phenytoin)
- Patient education — eat small, frequent meals; avoid caffeine, alcohol, smoking
5️⃣ ANTI-DIARRHEALS
Definition
Drugs used to reduce frequency/liquidity of stools or treat the underlying cause of diarrhea.
Classification
| Class | Examples |
|---|---|
| Opioid analogs (motility reducers) | Loperamide, Diphenoxylate + Atropine |
| Adsorbents | Kaolin + Pectin, Activated charcoal |
| Anticholinergics | Dicyclomine (hyoscine butylbromide) |
| Antibiotics | Furazolidone, Metronidazole, Ciprofloxacin |
| Bismuth compounds | Bismuth subsalicylate |
| ORS (Oral Rehydration Salts) | WHO-ORS, Pedialyte |
🔑 Loperamide (Imodium)
| Feature | Detail |
|---|---|
| Class | Opioid receptor agonist (μ-opioid) |
| Mechanism | Acts on opioid receptors in gut → reduces peristalsis + increases anal sphincter tone + reduces fluid secretion; does NOT cross BBB (no CNS effects) |
| Dose | 4 mg initially, then 2 mg after each loose stool; max 16 mg/day |
| Route | Oral |
Indications: Acute non-specific diarrhea, traveler's diarrhea, chronic diarrhea (IBD)
Contraindications: Dysentery (bloody diarrhea with fever), infants < 2 years, pseudomembranous colitis
Adverse Effects: Constipation, abdominal bloating, dry mouth
🔑 Diphenoxylate + Atropine (Lomotil)
| Feature | Detail |
|---|---|
| Mechanism | Opioid analog (reduces gut motility) + atropine (anticholinergic; added in sub-therapeutic dose to discourage abuse) |
| Dose | 5 mg QID |
| Route | Oral |
Adverse Effects: Sedation, dry mouth, urinary retention, blurred vision
Contraindications: Glaucoma, children < 2 years, obstructive jaundice
🔑 Dicyclomine (Dicycloverine) — Antispasmodic
| Feature | Detail |
|---|---|
| Class | Anticholinergic / Antimuscarinic |
| Mechanism | Blocks M3 muscarinic receptors in gut smooth muscle → reduces spasm and hypermotility |
| Dose | 10–20 mg TID/QID (oral); 20 mg IM |
| Route | Oral, IM |
| Indications | Irritable Bowel Syndrome (IBS), intestinal colic, diarrhea with spasm |
Contraindications: Myasthenia gravis, glaucoma, pyloric stenosis, urinary retention, infants < 6 months
Drug Interactions: Additive anticholinergic effects with antihistamines, TCAs, antipsychotics
Adverse Effects:
- Dry mouth, blurred vision, urinary retention
- Constipation, tachycardia, dizziness
- Elderly: Confusion, memory impairment
🔑 Furazolidone (Antibiotic Antidiarrheal)
| Feature | Detail |
|---|---|
| Class | Nitrofuran antibiotic |
| Mechanism | Inhibits bacterial enzymes (interferes with bacterial DNA) → bactericidal against enteric pathogens |
| Dose | 100 mg QID for 5–7 days |
| Route | Oral |
| Spectrum | Active against Salmonella, Shigella, Vibrio cholerae, Giardia, E. coli (enterotoxigenic) |
Indications: Bacterial diarrhea, traveler's diarrhea, Giardiasis, cholera
Contraindications: Infants < 1 month, MAO inhibitor use, G6PD deficiency
Drug Interactions:
- MAO inhibitor activity — avoid sympathomimetics (hypertensive crisis), alcohol (Antabuse-like reaction), tyramine-rich foods
- Enhances effect of oral hypoglycemics
Adverse Effects:
- Nausea, vomiting, headache
- Hemolytic anemia in G6PD deficiency
- Disulfiram-like reaction with alcohol
- Dark urine (brown-yellow coloration — harmless)
🔑 Kaolin + Pectin (Adsorbent Antidiarrheal)
| Feature | Detail |
|---|---|
| Mechanism | Kaolin (clay): adsorbs toxins, bacteria, water in gut; Pectin: coats intestinal mucosa protectively |
| Dose | 30–120 mL after each loose stool |
| Route | Oral |
Note: Adsorbs other drugs → take other medications 3–4 hours before or after kaolin-pectin
6️⃣ FLUID AND ELECTROLYTE THERAPY
Why It's Critical in Diarrhea
Diarrhea causes loss of water, Na+, K+, Cl⁻, HCO3⁻ → dehydration + metabolic acidosis
🔑 WHO Oral Rehydration Salts (ORS)
Composition of WHO-ORS per liter:
| Component | Amount |
|---|---|
| Sodium chloride (NaCl) | 2.6 g |
| Sodium citrate | 2.9 g |
| Potassium chloride (KCl) | 1.5 g |
| Glucose (anhydrous) | 13.5 g |
| Water | 1 liter |
Na+ = 75 mEq/L, K+ = 20 mEq/L, Glucose = 75 mmol/L
Mechanism: Glucose-coupled Na+ co-transport (SGLT1) is preserved in secretory diarrhea → absorption of Na+ drives water absorption (glucose-sodium cotransport)
Indications: Mild-to-moderate dehydration from diarrhea (cholera, acute gastroenteritis)
🔑 IV Fluids (for Severe Dehydration)
| Fluid | Use |
|---|---|
| Ringer's Lactate | Preferred in cholera, diarrhea (replaces electrolytes close to physiological) |
| Normal Saline (0.9% NaCl) | Dehydration without significant electrolyte loss |
| Dextrose-saline | Mild dehydration, maintenance |
Rule of thumb:
- Mild dehydration (< 5%): ORS only
- Moderate (5–10%): ORS + monitor
- Severe (> 10%): IV fluids immediately
WHO Dehydration Assessment (EXAM IMPORTANT!)
| Sign | Mild | Moderate | Severe |
|---|---|---|---|
| Thirst | Slight | Moderate | Very thirsty |
| Skin turgor | Normal | Reduced | Very reduced |
| Eyes | Normal | Sunken | Very sunken |
| Fontanelle (infant) | Normal | Depressed | Very depressed |
| Pulse | Normal | Weak & fast | Very weak/absent |
| BP | Normal | Low | Very low/shock |
| Urine | Normal | Reduced | None |
👩⚕️ Nurse's Responsibilities for Anti-Diarrheals & Fluid Therapy
- Assess dehydration status — check skin turgor, mucous membranes, urine output, vital signs
- Calculate fluid deficit and replace appropriately (ORS for mild-moderate, IV for severe)
- ORS preparation — teach caregivers correct preparation (1 sachet in exactly 1 liter boiled cooled water; do NOT add sugar or extra water)
- Furazolidone — warn about alcohol avoidance, MAO-like interactions; check for G6PD deficiency
- Dicyclomine — monitor for urinary retention especially in elderly men (BPH)
- Loperamide — DO NOT give if patient has bloody diarrhea/fever (may be invasive infection — antimotility drugs dangerous)
- Monitor I&O chart (input-output), daily weight, electrolytes
- IV access — maintain patent IV line in severe dehydration; use large-bore cannula
- Dietary advice — BRAT diet (Banana, Rice, Apple sauce, Toast); avoid dairy, spicy food during acute illness
- Hygiene education — handwashing, safe water, food safety (prevent reinfection)
- Pediatric caution — Diphenoxylate/Lomotil dangerous in children < 2; loperamide cautious in < 2 years
- Document — stool frequency, consistency, blood/mucus, urine output
📊 QUICK REVISION TABLE — All GI Drugs
| Drug | Class | Key Mechanism | Key Side Effect | Nurse Alert |
|---|---|---|---|---|
| Ipecac | Emetic | Irritates stomach + CTZ | Cardiotoxicity (emetine) | Don't give if unconscious/corrosive ingested |
| Ondansetron | Antiemetic (5-HT3) | Blocks serotonin receptors | QT prolongation | Give 30 min before chemo |
| Metoclopramide | Antiemetic (D2 blocker) | Blocks dopamine in CTZ + prokinetic | EPS, tardive dyskinesia | Monitor for involuntary movements |
| Promethazine | Antiemetic (H1 blocker) | Vestibular H1 blockade | Sedation | Fall precautions |
| Scopolamine | Antiemetic (Anticholinergic) | M2 blockade in vestibular | Dry mouth, blurred vision | Apply patch 4 hrs before travel |
| Bisacodyl | Laxative (stimulant) | Stimulates myenteric plexus | Cramps | Don't crush enteric-coated tabs |
| Lactulose | Laxative (osmotic) | Osmotic + acidifies colon | Flatulence | Used in hepatic encephalopathy |
| Liquid paraffin | Laxative (lubricant) | Coats stool | Fat-soluble vitamin deficiency | Avoid in elderly (aspiration risk) |
| Antacids (Al/Mg) | Antacid | Neutralizes HCl | Al → constipation; Mg → diarrhea | Space 2 hrs from other drugs |
| Omeprazole | PPI | Inhibits H+/K+-ATPase | Hypomagnesemia, B12 deficiency | Give 30–60 min before meals |
| Ranitidine | H2 blocker | Blocks H2 receptors | Fewer SE than cimetidine | Withdrawn due to NDMA |
| Cimetidine | H2 blocker | Blocks H2 receptors | CYP450 inhibition, gynecomastia | Monitor warfarin/phenytoin levels |
| Sucralfate | Mucosal protectant | Gel barrier on ulcer | Constipation | Give 30 min BEFORE food, on empty stomach |
| Misoprostol | Prostaglandin analog | Mucus + bicarb secretion | Diarrhea | CONTRAINDICATED in pregnancy! |
| Loperamide | Anti-diarrheal (opioid) | Reduces gut motility, no CNS effect | Constipation | Don't give in bloody/febrile diarrhea |
| Dicyclomine | Antispasmodic | M3 blockade → reduces spasm | Dry mouth, urinary retention | Caution in BPH, glaucoma |
| Furazolidone | Antibiotic | Inhibits bacterial enzymes | Hemolytic anemia (G6PD), disulfiram reaction | Avoid alcohol, check G6PD |
| ORS | Fluid/electrolyte | Glucose-Na cotransport | Hypernatremia (if overdone) | Exact 1L water per sachet |
🎯 HIGH-YIELD EXAM POINTS
- PPIs > H2 blockers > Antacids in acid suppression potency
- Omeprazole + Clopidogrel = dangerous interaction (reduces anti-platelet effect)
- Misoprostol is ABORTIFACIENT — never in pregnancy
- Cimetidine = most drug interactions among H2 blockers (CYP450 inhibitor)
- Sucralfate needs acidic environment — give on empty stomach, NOT with antacids
- Loperamide = no CNS effects (doesn't cross BBB) — safe, OTC anti-diarrheal
- Furazolidone has MAO inhibitor-like activity — avoid alcohol and tyramine foods
- Dicyclomine = anticholinergic — AVOID in glaucoma, BPH, myasthenia gravis
- Lactulose in hepatic encephalopathy — reduces ammonia absorption
- H. pylori triple therapy = PPI + Amoxicillin + Clarithromycin × 14 days
- Bulk laxatives (Psyllium) — MUST take with adequate water or may obstruct
- Liquid paraffin — risk of lipid pneumonia in elderly/bedridden → avoid
Sources: Katzung's Basic and Clinical Pharmacology, 16th Edition — Chapter 62: Drugs Used in the Treatment of Gastrointestinal Diseases
Kal ka paper ke liye ye sab zaroor yaad karo:
- Nurse's responsibilities har class ke saath (examiner specifically ask karta hai)
- Contraindications — especially misoprostol in pregnancy, laxatives in obstruction
- Drug interactions — cimetidine (CYP450), antacids (spacing rule), furazolidone (alcohol)
- Mechanism ek line mein — EMQs aur MCQs mein direct aata hai
- ORS composition — practical nursing mein critical hai
Best of luck kal ke paper mein! 🍀
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