STEPTRACKERPHARMACOLOGY + PULMONOLOGY | RESPIRATORY | HIGH-YIELD REVIEW

Asthma, COPD & Allergy Drugs

Airway drugs either relax smooth muscle (bronchodilators) or calm the inflammation that drives it (controllers); antihistamines and decongestants cover the upper airway.

FOCUS ON
β2 agonists: SABA (albuterol) rescue; LABA (salmeterol, formoterol) maintenance — never as monotherapy in asthma; tremor, tachycardia, ↓ K⁺. Inhaled corticosteroids (fluticasone, budesonide): mainstay controller in asthma; thrush, dysphonia; ICS-formoterol for both control and relief. Antimuscarinics: ipratropium (SAMA), tiotropium (LAMA — first-line COPD maintenance). Leukotriene modifiers: montelukast (CysLT1; aspirin-exacerbated, exercise asthma; neuropsychiatric effects), zafirlukast, zileuton (5-lipoxygenase; hepatotoxic). Methylxanthines: theophylline (PDE inhibitor, adenosine antagonist; narrow index, seizures, arrhythmias; CYP1A2). Roflumilast: PDE4 (severe COPD). Biologics: omalizumab (anti-IgE), mepolizumab/reslizumab (anti-IL-5), benralizumab (IL-5R), dupilumab (IL-4Rα), tezepelumab (TSLP). Cromolyn: mast-cell stabilizer. Antihistamines: 1st gen (diphenhydramine — sedating, anticholinergic); 2nd gen (loratadine, cetirizine, fexofenadine). Pulmonary fibrosis: pirfenidone, nintedanib. Cough: dextromethorphan, codeine, benzonatate.
DRUG
MECHANISM
USE
ADVERSE · NOTES
Albuterol · levalbuterol
Short-acting β2 agonist → ↑ cAMP → bronchodilation
Acute relief, exercise pretreatment, hyperkalemia
Tremor, tachycardia, ↓ K⁺; overuse = poor control
Salmeterol · formoterol
Long-acting β2 agonists
Asthma (always with ICS), COPD
Asthma deaths with LABA alone
Fluticasone · budesonide · beclomethasone
Inhaled glucocorticoids → ↓ airway inflammation
Persistent asthma (first-line controller), COPD with exacerbations/eosinophilia
Oral candidiasis, hoarseness, pneumonia (COPD), growth slowing in children
Ipratropium · tiotropium · umeclidinium
Muscarinic (M3) antagonists → ↓ bronchoconstriction, secretions
COPD (LAMA first-line), severe asthma add-on
Dry mouth, urinary retention, glaucoma
Montelukast · zafirlukast
CysLT1 receptor antagonists
Aspirin-exacerbated asthma, exercise-induced, allergic rhinitis
Neuropsychiatric events (boxed), Churg-Strauss unmasking
Zileuton
5-Lipoxygenase inhibitor → ↓ LTB4 and cysteinyl leukotrienes
Asthma (rare)
Hepatotoxicity — check LFTs
Theophylline
PDE inhibition (↑ cAMP), adenosine receptor block
Refractory asthma/COPD
Narrow index: nausea, seizures, arrhythmias; ↑ by ciprofloxacin, cimetidine; ↓ by smoking
Roflumilast
PDE4 inhibitor (anti-inflammatory)
Severe COPD with chronic bronchitis
Weight loss, diarrhea, depression
Omalizumab
Anti-IgE (free IgE) antibody
Severe allergic asthma, chronic urticaria
Anaphylaxis
Mepolizumab · benralizumab · dupilumab · tezepelumab
Anti-IL-5 · anti-IL-5R · anti-IL-4Rα · anti-TSLP
Severe eosinophilic or type 2 asthma; dupilumab atopic dermatitis
Injection reactions; dupilumab conjunctivitis
Cromolyn
Stabilizes mast cells
Prophylaxis of allergic asthma, mastocytosis
Very safe; no acute effect
1st- vs 2nd-generation H1 blockers
Diphenhydramine, hydroxyzine, chlorpheniramine vs loratadine, cetirizine, fexofenadine
Allergy, urticaria, sleep (1st), motion sickness (1st)
1st gen: sedation, anticholinergic, delirium in elderly
Pirfenidone · nintedanib
Antifibrotic (TGF-β ↓) · tyrosine kinase inhibitor
Idiopathic pulmonary fibrosis
Photosensitivity · diarrhea, hepatotoxicity
Guaifenesin · dextromethorphan · benzonatate
Expectorant · NMDA antagonist/σ agonist cough suppressant · local anesthetic
Cough
Dextromethorphan + MAOI/SSRI → serotonin syndrome

Mechanism — two routes to bronchodilation

β2 agonist → Gs → ↑ cAMP
→
Smooth muscle relaxes
Block M3 (Gq) on airway muscle
→
Less vagal bronchoconstriction

Theophylline and roflumilast keep cAMP high by blocking its breakdown (PDE).

Asthma vs COPD first steps

STEP
ASTHMA
COPD
Mild
As-needed ICS-formoterol
SABA / SAMA
Maintenance
ICS ± LABA
LAMA ± LABA
Severe
Add LAMA, biologic
Add ICS (eos), roflumilast, azithro

How it's tested

COMMON CONFUSIONMontelukast blocks the leukotriene receptor; zileuton blocks leukotriene synthesis — only zileuton is hepatotoxic.
THE TRAPTheophylline toxicity appears when a smoker quits or starts ciprofloxacin/erythromycin (less CYP1A2 metabolism) → seizures, arrhythmias.
YOUR APPROACHAsthma: anti-inflammatory controller first (ICS). COPD: long-acting bronchodilators first. Then add by phenotype.

If you see… think…

White oral plaques on an inhaler → inhaled corticosteroid candidiasis
Asthma drug with liver toxicity → zileuton
Nasal polyps + asthma after NSAIDs, preferred add-on → montelukast
Seizures in a COPD patient after ciprofloxacin → theophylline toxicity
Anti-IgE antibody → omalizumab
Eosinophilic asthma biologic → mepolizumab, benralizumab
First-line COPD maintenance → LAMA (tiotropium)
Asthma deaths with monotherapy → LABA alone
Antihistamine causing urinary retention in elderly → diphenhydramine
IPF antifibrotic causing photosensitivity → pirfenidone