Give me a proper notes of drugs for respiratory disorder

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💊 Drugs for Respiratory Disorders

Source: Katzung's Basic & Clinical Pharmacology, 16th Ed; Goodman & Gilman's Pharmacological Basis of Therapeutics

1. BETA-2 ADRENOCEPTOR AGONISTS (Bronchodilators)

Mechanism

Stimulate β₂ receptors on airway smooth muscle → activate adenylyl cyclase → ↑ cAMP → activate PKA → phosphorylate myosin light chain kinase → smooth muscle relaxation and bronchodilation.

Classification

A. Short-Acting β₂ Agonists (SABAs)

Drug	Route	Onset	Duration	Notes
Albuterol (Salbutamol)	Inhaler/Nebulizer	15 min	3–4 hrs	Drug of choice in acute asthmatic bronchospasm
Terbutaline	Inhaler/Oral	30 min	4–6 hrs	Also available orally; used in preterm labor
Metaproterenol	Inhaler	15 min	3–4 hrs	Less β₂-selective
Epinephrine	SC/Nebulizer	5 min	60–90 min	Non-selective (α + β); used mainly in anaphylaxis
Isoproterenol	Nebulizer	5 min	60–90 min	β₁ + β₂; largely replaced by β₂-selective agents

Key points:

Inhalation = best route (maximizes local effect, minimizes systemic toxicity)
Aerosol particles 2–5 μm are optimal for bronchial deposition
80–90% of inhaled dose is deposited in oropharynx

Toxicities: Tremor, tachycardia, hypokalemia; overdose → arrhythmias

B. Long-Acting β₂ Agonists (LABAs)

Drug	Duration	Notes
Salmeterol	12 hrs	Slow onset, primarily preventive; potentiates corticosteroid effects
Formoterol	12 hrs	Faster onset than salmeterol; can be used as rescue
Vilanterol	24 hrs	Used in combination inhalers (once daily)

⚠️ Warning: LABAs must not be used as monotherapy in asthma without an inhaled corticosteroid (ICS) — associated with increased asthma-related deaths when used alone.

2. INHALED CORTICOSTEROIDS (ICS)

Mechanism

Bind glucocorticoid receptors → alter gene expression → inhibit synthesis of inflammatory cytokines, chemokines, and adhesion molecules. Reduce airway hyperreactivity; do NOT directly relax smooth muscle.

Drugs

Drug	Potency Notes
Fluticasone propionate	Standard potency; multiple daily dosing
Fluticasone furoate	~2× more potent; once daily dosing
Beclomethasone	First ICS developed (1970s)
Budesonide	Also used in nebulizer form (children)
Ciclesonide	Prodrug activated by bronchial esterases; less oral candidiasis
Mometasone	Once-daily option
Triamcinolone	Less commonly used
Flunisolide	Standard potency

Clinical Use

Mild persistent asthma and above — cornerstone of chronic management
Reduce frequency of exacerbations; improve all indices of asthma control
Adjunct in COPD; intranasal for allergic rhinitis

Local Toxicities

Oropharyngeal candidiasis — treat with topical clotrimazole; use spacer + gargle after use
Dysphonia/Hoarseness — direct effect on vocal cords
Ciclesonide has lower incidence of both

Systemic Toxicities (with prolonged/high-dose use)

Osteoporosis, cataracts
In children: mild growth retardation (~1 cm/year, first year only)

3. SYSTEMIC CORTICOSTEROIDS

Drug	Route	Dose	Notes
Prednisone	Oral	30–60 mg/day	Severe exacerbations; taper over 5–10 days
Methylprednisolone	IV	0.5–1 mg/kg q6–12h	Acute severe asthma/status asthmaticus

Reserved for: severe exacerbations, patients unresponsive to bronchodilators, or COPD exacerbations. Long-term toxicities: Cushing's syndrome, diabetes, immunosuppression, adrenal suppression, osteoporosis.

4. ANTIMUSCARINIC (ANTICHOLINERGIC) AGENTS

Mechanism

Block M₃ muscarinic receptors on airway smooth muscle and submucosal glands → reduce bronchoconstriction and mucus secretion.

Classification

Short-Acting Muscarinic Antagonists (SAMAs)

Drug	Duration	Use
Ipratropium bromide	4–6 hrs	Acute COPD exacerbations; adjunct in severe acute asthma

Long-Acting Muscarinic Antagonists (LAMAs)

Drug	Duration	Use
Tiotropium bromide	24 hrs	First-line maintenance in COPD; add-on in uncontrolled asthma
Aclidinium	12 hrs	COPD maintenance
Glycopyrronium	24 hrs	COPD maintenance
Umeclidinium	24 hrs	COPD (often in combination inhalers)

Key Points

Preferred over β₂ agonists in COPD (cholinergic tone dominates)
Used in combination (LABA + LAMA) for moderate-severe COPD
Adverse effects: dry mouth, constipation, urinary retention, tachycardia, blurred vision (minimal with inhaled route — quaternary ammonium, poorly absorbed)

5. METHYLXANTHINES

Drugs

Theophylline (oral/IV)
Aminophylline (IV form — theophylline + ethylenediamine)

Mechanism

Inhibit phosphodiesterase → ↑ cAMP → bronchodilation
Adenosine receptor antagonism
Stimulate respiratory muscles (diaphragm)
Anti-inflammatory effects at low doses

Pharmacokinetics

Narrow therapeutic index: 10–20 mcg/mL (therapeutic range)
Metabolized by CYP1A2 — significant drug interactions
Half-life prolonged by: liver disease, heart failure, ciprofloxacin, erythromycin
Half-life shortened by: smoking, phenytoin, rifampin

Toxicity (dose-related)

Level (mcg/mL)	Toxicity
15–20	Nausea, vomiting, insomnia
20–40	Tachycardia, arrhythmias, headache
> 40	Seizures, severe arrhythmias (life-threatening)

Clinical Use

Third-line bronchodilator in asthma and COPD (largely replaced by inhaled agents)
Still used in resource-limited settings and COPD with respiratory muscle fatigue

6. LEUKOTRIENE PATHWAY INHIBITORS

Classification

A. 5-Lipoxygenase (5-LOX) Inhibitor

Drug	Mechanism	Use
Zileuton	Inhibits 5-LOX → ↓ leukotriene synthesis (LTB₄, LTC₄, LTD₄, LTE₄)	Mild-moderate asthma; aspirin-exacerbated asthma

B. Leukotriene Receptor Antagonists (LTRAs)

Drug	Mechanism	Notes
Montelukast	Blocks CysLT₁ receptors	Oral, once daily; children ≥1 yr; also allergic rhinitis
Zafirlukast	Blocks CysLT₁ receptors	Inhibits CYP2C9; drug interactions
Pranlukast	Blocks CysLT₁ receptors	Less commonly used

Clinical Use

Mild persistent asthma (alternative to ICS)
Aspirin-sensitive asthma (first-line)
Allergic rhinitis (montelukast)
Exercise-induced bronchospasm
Less effective than ICS but well-tolerated (oral agents)

⚠️ Montelukast black box warning (2020): Risk of serious neuropsychiatric events (suicidal ideation, behavioral changes) — reserve for patients intolerant of ICS/LABA.

7. MAST CELL STABILIZERS

Drug	Mechanism	Use
Cromolyn sodium	Stabilizes mast cell membranes, blocks chloride channels → prevents degranulation	Prophylaxis only (NOT acute); exercise-induced asthma; allergic rhinitis (intranasal)
Nedocromil (discontinued in many countries)	Similar to cromolyn	Mild-moderate asthma prophylaxis

Key point: Cromolyn is NOT absorbed systemically → minimal toxicity (cough from inhalation). Has NO role in acute bronchospasm.

8. BIOLOGICS / MONOCLONAL ANTIBODIES

Anti-IgE

Drug	Target	Use
Omalizumab	Anti-IgE (binds free IgE, prevents binding to mast cells)	Moderate-severe allergic asthma uncontrolled on ICS; chronic urticaria

Anti-IL-5 / Anti-Eosinophil

Drug	Target	Notes
Mepolizumab	Anti-IL-5	SC injection; severe eosinophilic asthma; eosinophilic COPD
Reslizumab	Anti-IL-5	IV infusion
Benralizumab	Anti-IL-5Rα (receptor)	SC; faster eosinophil depletion

Anti-IL-4/IL-13

Drug	Target	Notes
Dupilumab	Blocks IL-4Rα (shared receptor for IL-4 and IL-13)	Severe type 2 asthma; also atopic dermatitis, CRS with nasal polyps

Anti-TSLP

Drug	Target	Notes
Tezepelumab	Anti-TSLP (thymic stromal lymphopoietin)	Broadest biologic — effective regardless of eosinophil count

Key Points

All biologics are SC or IV injections, given every 2–8 weeks
Reserved for Step 5–6 severe uncontrolled asthma
Select based on biomarker profile (IgE, blood eosinophils, FeNO)

9. PHOSPHODIESTERASE-4 (PDE-4) INHIBITORS

Drug	Use	Notes
Roflumilast (oral)	Severe COPD with chronic bronchitis and frequent exacerbations	Anti-inflammatory; reduces exacerbation frequency; does NOT cause bronchodilation directly

Adverse effects: Nausea, diarrhea, weight loss, neuropsychiatric effects (depression, insomnia)

10. ANTITUSSIVES (Cough Suppressants)

Drug	Mechanism	Notes
Codeine	Opioid μ-receptor agonist; suppresses cough center in medulla	Standard; potential for dependence
Dextromethorphan	NMDA antagonist; non-opioid cough suppressant	OTC; no analgesic effect; can cause serotonin syndrome with MAOIs
Benzonatate	Inhibits stretch receptors in lung parenchyma	Non-opioid; oral capsules; do NOT chew (anesthesia of oropharynx)

11. EXPECTORANTS & MUCOLYTICS

Drug	Class	Mechanism	Use
Guaifenesin	Expectorant	↑ secretion volume → ↓ viscosity; stimulates mucociliary clearance	Productive cough in URTI; bronchitis
Acetylcysteine (NAC)	Mucolytic	Breaks disulfide bonds in mucus glycoproteins → ↓ viscosity	Cystic fibrosis; COPD with thick secretions; also used in paracetamol overdose
Ambroxol	Mucolytic/Secretolytic	↑ Surfactant production; stimulates mucus secretion	Chronic bronchitis, COPD
Bromhexine	Mucolytic	Depolymerizes mucopolysaccharides; prodrug of ambroxol	Bronchitis, COPD
Dornase alfa	Mucolytic	Recombinant DNase; cleaves extracellular DNA in mucus	Cystic fibrosis specifically

12. ANTIHISTAMINES (H₁ Blockers) — Respiratory Use

1st Generation (Sedating)

Drug	Notes
Diphenhydramine	Sedating; drying effect; urticaria, anaphylaxis
Chlorpheniramine	Allergic rhinitis; less sedating than diphenhydramine
Promethazine	Antiemetic + antihistamine; significant anticholinergic effects

2nd Generation (Non-Sedating)

Drug	Notes
Cetirizine	Allergic rhinitis, urticaria; minimal sedation
Loratadine	Non-sedating; no CYP interaction
Fexofenadine	Least CNS penetration; safest in pilots/drivers
Desloratadine	Active metabolite of loratadine

Key: Antihistamines are useful for allergic rhinitis and urticaria but have minimal role in asthma (no effect on bronchoconstriction).

13. DRUGS FOR PULMONARY HYPERTENSION

Class	Drug	Mechanism
PDE-5 inhibitors	Sildenafil, Tadalafil	↑ cGMP → vasodilation
Endothelin receptor antagonists	Bosentan, Ambrisentan, Macitentan	Block ET-1 vasoconstriction
Prostacyclin analogs	Epoprostenol, Iloprost, Treprostinil	Vasodilation + inhibit platelet aggregation
Guanylate cyclase stimulator	Riociguat	↑ cGMP independently and in synergy with NO

14. DRUGS FOR CYSTIC FIBROSIS (CFTR Modulators)

Drug	Mechanism	Mutation Target
Ivacaftor	CFTR potentiator (opens abnormal channel)	G551D and other gating mutations
Lumacaftor	CFTR corrector (helps protein folding)	F508del (homozygous)
Tezacaftor	CFTR corrector	F508del
Elexacaftor/Tezacaftor/Ivacaftor (Trikafta)	Triple combination	F508del (≥1 copy) — most patients

QUICK SUMMARY TABLE — Drug Selection by Condition

Condition	First-Line	Add-On
Acute asthma	SABA (albuterol)	Systemic steroids, ipratropium
Mild persistent asthma	Low-dose ICS	LTRA
Moderate persistent	ICS + LABA	Tiotropium, biologic
Severe uncontrolled	ICS + LABA + LAMA	Biologic (dupilumab, omalizumab, etc.)
COPD stable	LAMA or LABA	Combine LAMA+LABA; add ICS if eosinophilic
COPD exacerbation	SABA + SAMA	Systemic steroids ± antibiotics
Allergic rhinitis	Intranasal corticosteroid	2nd-gen antihistamine
Aspirin-sensitive asthma	Montelukast / Zileuton	ICS
Cystic fibrosis	CFTR modulator (Trikafta)	DNase alfa, NAC

Sources: Katzung's Basic & Clinical Pharmacology, 16th Ed (McGraw-Hill) | Goodman & Gilman's Pharmacological Basis of TherapeuticsThese notes cover 14 drug categories for respiratory disorders, compiled from Katzung's Basic & Clinical Pharmacology (16th Ed) and Goodman & Gilman's. Here's a quick overview of what's included:

β₂ Agonists — SABAs (albuterol, terbutaline) and LABAs (salmeterol, formoterol, vilanterol) with mechanisms, routes, toxicities
Inhaled Corticosteroids — All agents (fluticasone, budesonide, ciclesonide, etc.), local vs systemic toxicities, clinical use
Systemic Corticosteroids — Prednisone and methylprednisolone doses for acute severe asthma
Antimuscarinics — SAMAs (ipratropium) and LAMAs (tiotropium, umeclidinium, aclidinium, glycopyrronium); key role in COPD
Methylxanthines — Theophylline/aminophylline with narrow therapeutic index and drug interactions
Leukotriene Inhibitors — Zileuton (5-LOX inhibitor) and LTRAs (montelukast, zafirlukast) including black box warning
Mast Cell Stabilizers — Cromolyn (prophylaxis only, not for acute)
Biologics — Omalizumab, mepolizumab, dupilumab, tezepelumab and selection by biomarker
PDE-4 Inhibitors — Roflumilast for severe COPD
Antitussives — Codeine, dextromethorphan, benzonatate
Mucolytics/Expectorants — Acetylcysteine, guaifenesin, ambroxol, dornase alfa
Antihistamines — 1st vs 2nd generation, role in allergic rhinitis
Pulmonary Hypertension drugs — Sildenafil, bosentan, epoprostenol, riociguat
CFTR Modulators — Trikafta (elexacaftor/tezacaftor/ivacaftor) for cystic fibrosis

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