Pharmacology of drugs acting on the respiratory system covers mechanisms, pharmacokinetics, therapeutic uses and adverse effects of bronchodilators, anti‑inflammatory agents, mucolytics and antitussives. This concise, exam-focused guide helps B. Pharm students understand beta‑2 agonists, anticholinergics, methylxanthines, inhaled corticosteroids, leukotriene modifiers, cromones and newer agents like PDE4 inhibitors. Emphasis is on receptor targets, onset/duration, routes (inhalation, oral, IV), major drug interactions (CYP-mediated), and monitoring for toxicity. Clinical implications for asthma, COPD, cough and allergic rhinitis are integrated with key drug profiles and side effects to build solid applied knowledge. Study these concepts to excel in therapeutics and examinations. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. Which receptor subtype mediates bronchodilation when activated by beta-2 agonists?
- Beta-1 adrenergic receptor
- Beta-2 adrenergic receptor
- Alpha-1 adrenergic receptor
- M3 muscarinic receptor
Correct Answer: Beta-2 adrenergic receptor
Q2. Which drug is a short-acting beta-2 agonist commonly used for acute asthma relief?
- Salmeterol
- Formoterol
- Salbutamol (albuterol)
- Tiotropium
Correct Answer: Salbutamol (albuterol)
Q3. Tiotropium produces bronchodilation primarily by blocking which receptor?
- M2 muscarinic receptor
- M3 muscarinic receptor
- B2 adrenergic receptor
- H1 histamine receptor
Correct Answer: M3 muscarinic receptor
Q4. Theophylline exerts bronchodilator effects mainly by which mechanism?
- Inhibition of phosphodiesterase leading to increased cAMP
- Direct stimulation of alpha receptors
- Blocking leukotriene receptors
- Inhibition of histamine H1 receptors
Correct Answer: Inhibition of phosphodiesterase leading to increased cAMP
Q5. Which enzyme primarily metabolizes theophylline and is inducible by smoking?
- CYP3A4
- CYP2D6
- CYP1A2
- CYP2C9
Correct Answer: CYP1A2
Q6. Montelukast treats asthma by antagonizing which receptor?
- H1 histamine receptor
- CysLT1 leukotriene receptor
- Beta-2 adrenergic receptor
- 5-HT3 receptor
Correct Answer: CysLT1 leukotriene receptor
Q7. Zileuton improves asthma by inhibiting which step in leukotriene synthesis?
- COX-1 enzyme
- 5-lipoxygenase (5-LOX)
- LTC4 synthase
- Phospholipase A2
Correct Answer: 5-lipoxygenase (5-LOX)
Q8. Which inhaled corticosteroid adverse effect is most commonly local to the oropharynx?
- Adrenal suppression
- Oral candidiasis (thrush)
- Osteoporosis
- Hyperglycemia
Correct Answer: Oral candidiasis (thrush)
Q9. Long-acting beta-2 agonists (LABAs) should not be used as monotherapy in asthma because:
- They have very short duration of action
- They increase risk of asthma-related deaths if used without inhaled corticosteroids
- They cause severe bronchoconstriction acutely
- They block leukotriene receptors
Correct Answer: They increase risk of asthma-related deaths if used without inhaled corticosteroids
Q10. Roflumilast, used in COPD, acts by inhibiting which target?
- Phosphodiesterase-4 (PDE4)
- Beta-2 receptor
- 5-lipoxygenase
- Histone deacetylase
Correct Answer: Phosphodiesterase-4 (PDE4)
Q11. Cromolyn sodium prevents bronchoconstriction primarily by:
- Stimulating beta-2 receptors
- Inhibiting mast cell degranulation
- Blocking muscarinic receptors
- Inhibiting leukotriene synthesis
Correct Answer: Inhibiting mast cell degranulation
Q12. Which antitussive acts as a central NMDA receptor antagonist and sigma-1 agonist, commonly used as a cough suppressant?
- Codeine
- Dextromethorphan
- Guaifenesin
- Acetylcysteine
Correct Answer: Dextromethorphan
Q13. Acetylcysteine helps in respiratory disease mainly by:
- Stimulating cough reflex
- Breaking disulfide bonds in mucus to reduce viscosity
- Blocking histamine release
- Inhibiting phosphodiesterase
Correct Answer: Breaking disulfide bonds in mucus to reduce viscosity
Q14. Which oral antihistamine is least sedating due to minimal blood–brain barrier penetration?
- Diphenhydramine
- Chlorpheniramine
- Loratadine
- Promethazine
Correct Answer: Loratadine
Q15. A major toxicity of high theophylline concentrations includes:
- Hypoglycemia and bradycardia
- Seizures and cardiac arrhythmias
- Renal failure
- Severe sedation only
Correct Answer: Seizures and cardiac arrhythmias
Q16. Which antibiotic interaction can increase theophylline levels and risk toxicity?
- Rifampicin
- Carbamazepine
- Ciprofloxacin
- Phenytoin
Correct Answer: Ciprofloxacin
Q17. Which agent is a muscarinic antagonist used for COPD with a prolonged duration due to slow dissociation from M3 receptors?
- Ipratropium bromide
- Tiotropium bromide
- Oxitropium
- Atropine sulfate
Correct Answer: Tiotropium bromide
Q18. Which drug class reduces airway inflammation by inhibiting multiple inflammatory genes via glucocorticoid receptor–mediated effects?
- Leukotriene receptor antagonists
- Inhaled corticosteroids
- Methylxanthines
- Beta-2 agonists
Correct Answer: Inhaled corticosteroids
Q19. A patient on montelukast reports mood changes; this adverse effect is best described as:
- Hepatotoxicity
- Neuropsychiatric events
- Renal impairment
- QT prolongation
Correct Answer: Neuropsychiatric events
Q20. Guaifenesin is classified pharmacologically as a:
- Mucolytic that cleaves disulfide bonds
- Expectorant that increases respiratory tract secretions
- Central antitussive
- Beta-2 agonist
Correct Answer: Expectorant that increases respiratory tract secretions
Q21. Which inhaled drug has a rapid onset suitable for exercise-induced bronchospasm prophylaxis?
- Salmeterol (slow onset)
- Formoterol (fast onset LABA)
- Beclomethasone
- Montelukast (oral, not rapid inhaled)
Correct Answer: Formoterol (fast onset LABA)
Q22. Which drug is an opioid that suppresses cough via mu-opioid receptors and can cause respiratory depression?
- Dextromethorphan
- Codeine
- Benzonatate
- Acetylcysteine
Correct Answer: Codeine
Q23. Inhaled corticosteroids at high systemic exposure may cause all except:
- Adrenal suppression
- Osteoporosis
- Hyperglycemia
- Immediate bronchospasm due to histamine release
Correct Answer: Immediate bronchospasm due to histamine release
Q24. Which drug class is contraindicated or used cautiously in patients with glaucoma because of anticholinergic effects?
- Beta-2 agonists
- Antimuscarinic bronchodilators
- Inhaled corticosteroids
- Leukotriene antagonists
Correct Answer: Antimuscarinic bronchodilators
Q25. A patient on SSRIs develops agitation after starting dextromethorphan; this interaction is due to risk of:
- Serotonin syndrome
- Hemolytic anemia
- QT prolongation only
- ACE inhibitor cough
Correct Answer: Serotonin syndrome
Q26. Which agent reduces mucus viscosity by providing free thiol groups and serves also as an antidote for acetaminophen overdose?
- Guaifenesin
- N-acetylcysteine (NAC)
- Ambroxol
- Dornase alfa
Correct Answer: N-acetylcysteine (NAC)
Q27. In acute severe asthma, intravenous magnesium sulfate helps by:
- Acting as a bronchodilator through smooth muscle relaxation
- Directly inhibiting leukotriene synthesis
- Blocking beta receptors
- Stimulating cortisol release
Correct Answer: Acting as a bronchodilator through smooth muscle relaxation
Q28. Which of the following best describes budesonide when used for asthma?
- Short-acting bronchodilator
- Inhaled corticosteroid with high topical potency and low systemic bioavailability
- Oral leukotriene antagonist
- PDE4 inhibitor for acute bronchospasm
Correct Answer: Inhaled corticosteroid with high topical potency and low systemic bioavailability
Q29. Which class of drugs can precipitate bronchospasm in aspirin-exacerbated respiratory disease (AERD)?
- Beta-2 agonists
- NSAIDs that inhibit COX-1
- Anticholinergics
- Inhaled corticosteroids
Correct Answer: NSAIDs that inhibit COX-1
Q30. A clinician wants to minimize systemic corticosteroid effects while treating chronic asthma; which strategy is most appropriate?
- Use high-dose oral prednisone daily
- Prefer inhaled corticosteroids with spacer and mouth rinse
- Replace steroids with high-dose theophylline
- Use oral leukotriene inhibitors in all severe cases instead of steroids
Correct Answer: Prefer inhaled corticosteroids with spacer and mouth rinse
I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.
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