Respiratory System Drugs — MCQs

Respiratory System Drugs Indian Medical PG Practice Questions and MCQs

Question 181: Which of the following drugs is NOT used in the management of acute asthma?

A. Salbutamol
B. Ipratropium
C. Montelukast (Correct Answer)
D. Hydrocortisone

Explanation: ### Explanation The management of **acute asthma exacerbations** requires drugs with a rapid onset of action to reverse bronchoconstriction and reduce airway inflammation immediately. **Why Montelukast is the correct answer:** Montelukast is a **Leukotriene Receptor Antagonist (LTRA)**. While it is highly effective for the **prophylaxis** and chronic management of asthma (especially aspirin-induced and exercise-induced asthma), it has a **slow onset of action** (taking hours to days for full effect). Therefore, it has no role in the emergency management of an acute attack where immediate bronchodilation is required. **Analysis of incorrect options:** * **Salbutamol (SABA):** The drug of choice for acute asthma. It acts on $\beta_2$ receptors to cause rapid bronchodilation within 5–15 minutes. * **Ipratropium (SAMA):** An anticholinergic that blocks M3 receptors. It is used as an add-on to Salbutamol in acute severe asthma (synergistic effect) to further reduce airflow obstruction. * **Hydrocortisone:** A systemic corticosteroid used in acute severe asthma to reduce airway inflammation and prevent late-phase responses. While it takes 4–6 hours to act, it is a standard component of acute management protocols. **High-Yield NEET-PG Pearls:** 1. **Drug of Choice (DOC) for Acute Asthma:** Inhaled Salbutamol (SABA). 2. **DOC for Chronic Maintenance:** Inhaled Corticosteroids (e.g., Fluticasone, Budesonide). 3. **DOC for Aspirin-Induced Asthma:** Montelukast/Zafirlukast. 4. **Zileuton:** A 5-Lipoxygenase inhibitor (different mechanism than Montelukast) also used for prophylaxis. 5. **Magnesium Sulfate:** Used intravenously in life-threatening asthma non-responsive to initial therapy.

Question 182: Omalizumab is a monoclonal antibody used for the treatment of:

A. Digitalis toxicity
B. Bronchial asthma (Correct Answer)
C. Rheumatoid arthritis
D. Breast carcinoma

Explanation: **Explanation:** **Omalizumab** is a recombinant DNA-derived humanized monoclonal antibody specifically designed for the management of moderate-to-severe persistent **Bronchial Asthma** [1]. **Why Bronchial Asthma is Correct:** The underlying mechanism involves Omalizumab binding specifically to the **Fc region of free circulating IgE** (Immunoglobulin E) [1]. By doing so, it prevents IgE from binding to its high-affinity receptors (FcεRI) on the surface of mast cells and basophils [2]. This prevents the degranulation of these cells and the subsequent release of inflammatory mediators (like histamine and leukotrienes) that trigger an asthma attack [2]. It is particularly indicated for patients with allergic asthma who are inadequately controlled with inhaled corticosteroids [1]. **Why Other Options are Incorrect:** * **Digitalis Toxicity:** This is treated with **Digoxin Immune Fab (Digibind)**, which are fragments of antibodies that bind to and neutralize digoxin. * **Rheumatoid Arthritis:** Common monoclonal antibodies used here include **Infliximab, Adalimumab** (anti-TNFα), or **Rituximab** (anti-CD20). * **Breast Carcinoma:** The classic monoclonal antibody used is **Trastuzumab (Herceptin)**, which targets the HER2/neu receptor. **High-Yield Clinical Pearls for NEET-PG:** * **Route of Administration:** It is administered **subcutaneously** every 2–4 weeks. * **Black Box Warning:** It carries a risk of **anaphylaxis**, so patients must be monitored after injection. * **Target:** It only binds to *free* IgE; it does not bind to IgE already bound to mast cells, thus it does not trigger anaphylaxis itself. * **Other Indications:** It is also FDA-approved for **Chronic Spontaneous Urticaria (CSU)** and nasal polyps [1].

Question 183: Beta-agonists in asthma act by which of the following mechanisms, except?

A. Cause bronchodilatation
B. Abort an acute attack
C. Decrease inflammation (Correct Answer)
D. All of the above

Explanation: ### Explanation **Mechanism of Action:** Beta-2 ($\beta_2$) agonists (like Salbutamol and Salmeterol) act by stimulating $\beta_2$ receptors on bronchial smooth muscle. This activates the enzyme **adenylyl cyclase**, increasing intracellular **cAMP** levels. Elevated cAMP leads to the activation of Protein Kinase A, which causes smooth muscle relaxation and potent **bronchodilatation**. **Why "Decrease inflammation" is the correct answer:** While $\beta_2$ agonists are excellent bronchodilators, they have **no significant anti-inflammatory effect**. They do not inhibit the late-phase inflammatory response or reduce airway hyper-responsiveness over time. In asthma management, inflammation is primarily addressed by **Corticosteroids**, not $\beta_2$ agonists. **Analysis of Incorrect Options:** * **Option A (Cause bronchodilatation):** This is the primary physiological effect of $\beta_2$ agonists. They are the most potent bronchodilators available. * **Option B (Abort an acute attack):** Short-Acting Beta-Agonists (SABAs) like Salbutamol have a rapid onset of action (2–5 minutes), making them the "rescue" drugs of choice to abort acute bronchospasm. * **Option D (All of the above):** Incorrect, as the drugs lack anti-inflammatory properties. **NEET-PG High-Yield Pearls:** * **Drug of Choice (DOC):** SABAs are the DOC for acute asthma attacks and exercise-induced bronchospasm. * **Side Effects:** Muscle tremors (most common, due to $\beta_2$ stimulation in skeletal muscles), tachycardia (due to $\beta_1$ cross-reactivity), and **hypokalemia** (due to K+ shifting into cells). * **Tolerance:** Prolonged use can lead to "tachyphylaxis" due to the down-regulation of $\beta_2$ receptors. * **LABAs:** Salmeterol and Formoterol are Long-Acting Beta-Agonists used for maintenance, never as monotherapy (always combined with inhaled steroids).

Question 184: Montelukast is:

A. Selective antagonist of the leukotriene receptor (Correct Answer)
B. Lipooxygenase inhibitor
C. H1 antagonist
D. H3 antagonist

Explanation: **Explanation:** **Montelukast** is a potent and selective **CysLT1 receptor antagonist**. It works by blocking the action of cysteinyl leukotrienes (LTC4, LTD4, and LTE4) at their primary receptor site. These leukotrienes are powerful inflammatory mediators released from mast cells and eosinophils that cause bronchoconstriction, increased mucus secretion, and mucosal edema. By antagonizing these receptors, Montelukast effectively prevents airway narrowing and inflammation. **Analysis of Options:** * **Option A (Correct):** Montelukast (and Zafirlukast) specifically targets the CysLT1 receptor, making it a selective leukotriene receptor antagonist (LTRA). * **Option B:** **Zileuton** is the drug that acts as a 5-Lipoxygenase (5-LOX) inhibitor, preventing the synthesis of leukotrienes from arachidonic acid. * **Option C:** H1 antagonists are antihistamines (e.g., Cetirizine, Loratadine) used primarily for allergic rhinitis and urticaria, not as mainstay therapy for asthma. * **Option D:** H3 antagonists (e.g., Pitolisant) are involved in neurotransmitter regulation and are used in conditions like narcolepsy. **High-Yield Clinical Pearls for NEET-PG:** * **Indications:** Prophylaxis of bronchial asthma, exercise-induced bronchospasm, and aspirin-induced asthma (where leukotriene production is shunted/increased). * **Administration:** It is administered **orally**, usually once daily in the evening. * **Adverse Effects:** Generally well-tolerated, but watch for **Churg-Strauss syndrome** (eosinophilic granulomatosis with polyangiitis) and neuropsychiatric side effects (mood changes, suicidal ideation—FDA Boxed Warning). * **Comparison:** Unlike Zafirlukast, Montelukast does not significantly inhibit CYP2C9 or CYP3A4 enzymes, leading to fewer drug interactions.

Question 185: What is the mechanism of action of Montelukast?

A. Inhibition of leukotriene production (Correct Answer)
B. Inhibits alpha receptors
C. Beta receptor agonist
D. Phosphodiesterase inhibition

Explanation: **Explanation:** **Mechanism of Action:** Montelukast is a **Leukotriene Receptor Antagonist (LTRA)**. Specifically, it works by competitively and selectively inhibiting the **CysLT1 receptor**. By blocking this receptor, it prevents the actions of cysteinyl leukotrienes (LTC4, LTD4, and LTE4), which are potent inflammatory mediators. This leads to a reduction in bronchoconstriction, airway edema, and mucus secretion, making it effective in the management of bronchial asthma. **Analysis of Options:** * **Option A (Correct):** By blocking the receptor, Montelukast effectively inhibits the physiological effects of leukotriene production in the airways. (Note: While Zileuton inhibits the *synthesis* via 5-LOX, LTRAs like Montelukast are clinically categorized under the umbrella of leukotriene modifiers/inhibitors). * **Option B:** Alpha-receptor inhibitors (e.g., Prazosin) are used for hypertension or BPH, not for asthma. * **Option C:** Beta-2 agonists (e.g., Salbutamol, Salmeterol) act by stimulating receptors to increase cAMP, causing direct bronchodilation. * **Option D:** Phosphodiesterase (PDE) inhibition is the mechanism for **Theophylline** (non-selective) or **Roflumilast** (PDE-4 selective). **High-Yield Clinical Pearls for NEET-PG:** 1. **Churg-Strauss Syndrome:** A rare but high-yield association; patients switching from oral steroids to Montelukast may unmask this systemic vasculitis. 2. **Aspirin-Induced Asthma:** LTRAs are the **drugs of choice** for Aspirin-Exacerbated Respiratory Disease (AERD). 3. **Exercise-Induced Bronchospasm:** Montelukast is effective for prophylaxis in these patients. 4. **Neuropsychiatric Side Effects:** The FDA has issued a boxed warning for Montelukast regarding serious mental health side effects (e.g., agitation, aggression, suicidal ideation).

Question 186: A 55-year-old female who is taking propranolol for the management of a cardiovascular disease experiences an acute asthmatic attack. Which of the following drugs would be most appropriate to manage this asthmatic attack?

A. Cromolyn sodium
B. Salbutamol
C. Beclomethasone
D. Ipratropium bromide (Correct Answer)

Explanation: **Explanation:** The core clinical challenge in this scenario is **Beta-blocker induced bronchospasm**. Propranolol is a non-selective beta-blocker that inhibits $\beta_2$ receptors in the bronchial smooth muscle, leading to bronchoconstriction. **1. Why Ipratropium Bromide is the correct answer:** In patients taking beta-blockers, $\beta_2$ agonists (like Salbutamol) are often ineffective because the receptors are competitively occupied/blocked by the drug. Therefore, the preferred alternative for acute relief is an **Anticholinergic (Muscarinic antagonist)** like **Ipratropium bromide**. It works by blocking M3 receptors, inhibiting the parasympathetic-mediated bronchoconstriction, which remains an open pathway for bronchodilation despite beta-blockade. **2. Why other options are incorrect:** * **Salbutamol:** As a $\beta_2$ agonist, its action is directly antagonized by Propranolol. It will fail to provide rapid relief in this specific patient. * **Cromolyn sodium:** This is a mast cell stabilizer used for **prophylaxis** (prevention) of asthma. It has no role in managing an acute attack as it does not cause bronchodilation. * **Beclomethasone:** This is an inhaled corticosteroid used for **long-term control** of airway inflammation. It has a slow onset of action and is not used for acute "rescue" therapy. **Clinical Pearls for NEET-PG:** * **Drug of Choice (DOC):** For acute asthma in patients on beta-blockers, the DOC is **Ipratropium bromide**. * **Mechanism:** Ipratropium is a quaternary ammonium compound; it is poorly absorbed systemically, leading to fewer side effects (like tachycardia) compared to atropine. * **Contraindication:** Non-selective beta-blockers (Propranolol, Nadolol, Timolol) are strictly contraindicated in asthmatics. If a beta-blocker is mandatory, cardioselective agents (e.g., Metoprolol, Atenolol) are preferred, though still used with caution.

Question 187: Reslizumab is used in which of the following conditions?

A. Psoriasis
B. RSV infection
C. Asthma (Correct Answer)
D. Crohn's disease

Explanation: **Explanation:** **Reslizumab** is a humanized monoclonal antibody specifically designed to target and neutralize **Interleukin-5 (IL-5)**. IL-5 is the primary cytokine responsible for the growth, differentiation, recruitment, and activation of eosinophils. By binding to IL-5, Reslizumab prevents it from interacting with its receptor on the eosinophil surface, thereby reducing blood and tissue eosinophilia. It is FDA-approved as an add-on maintenance treatment for patients with **severe eosinophilic asthma** who are not adequately controlled on standard therapies. **Analysis of Options:** * **Option A (Psoriasis):** Psoriasis is typically treated with biologics targeting TNF-α (Infliximab), IL-17 (Secukinumab), or IL-23 (Ustekinumab). * **Option B (RSV infection):** The monoclonal antibody used for the prevention of Respiratory Syncytial Virus (RSV) in high-risk infants is **Palivizumab** (targets the RSV F protein). * **Option D (Crohn’s disease):** Management involves biologics targeting TNF-α (Adalimumab) or integrins (Vedolizumab). **High-Yield Clinical Pearls for NEET-PG:** * **Anti-IL-5 Agents:** Remember the trio—**Reslizumab, Mepolizumab** (both target IL-5 ligand), and **Benralizumab** (targets the IL-5 receptor alpha). * **Route of Administration:** Unlike Mepolizumab (subcutaneous), Reslizumab is administered via **intravenous (IV) infusion**. * **Black Box Warning:** Reslizumab carries a risk of **anaphylaxis**; patients must be monitored closely during and after infusion. * **Omalizumab:** Another high-yield asthma biologic that targets **IgE** (used in allergic asthma).

Question 188: Which of the following antitussives is present in opium but has no analgesic or addicting properties?

A. Codeine
B. Pholcodeine
C. Noscapine (Correct Answer)
D. Ethylmorphine

Explanation: **Explanation:** **Noscapine** is a benzylisoquinoline alkaloid naturally found in **opium**. Unlike morphine or codeine, it does not act on opioid receptors ($\mu$, $\delta$, or $\kappa$). Consequently, it is completely devoid of analgesic, euphoric, or addicting properties. It acts as a potent antitussive by suppressing the cough reflex through non-opioid mechanisms. It is particularly useful in spasmodic cough, though it may occasionally release histamine, causing bronchoconstriction in asthmatics. **Analysis of Incorrect Options:** * **Codeine (Methylmorphine):** This is the "gold standard" antitussive. While it is an opium alkaloid, it acts on $\mu$-opioid receptors, leading to side effects like constipation, respiratory depression, and a potential for addiction/abuse. * **Pholcodeine:** A semi-synthetic derivative of morphine. While it has negligible analgesic properties and is less addicting than codeine, it is **not** naturally present in opium; it is synthesized. * **Ethylmorphine:** Similar to codeine, it is a semi-synthetic opioid with significant sedative and potential addictive properties. **High-Yield NEET-PG Pearls:** * **Noscapine** is also known as "Narcotine," but this is a misnomer as it lacks narcotic effects. * **Dextromethorphan** is another common non-analgesic antitussive, but it is a synthetic derivative, not an opium alkaloid. * **Benzonatate** is a peripherally acting antitussive that works by anesthetizing stretch receptors in the lungs. * **Contraindication:** Avoid Noscapine and other cough suppressants in productive coughs, as they can lead to sputum retention and secondary infections.

Question 189: Which of the following drugs is a second-generation antihistamine?

A. Promethazine
B. Loratadine (Correct Answer)
C. Diphenhydramine
D. Doxylamine

Explanation: ### Explanation **Correct Option: B. Loratadine** **Underlying Medical Concept:** Antihistamines (H1-receptor antagonists) are classified into two generations based on their ability to cross the blood-brain barrier (BBB) and their selectivity for H1 receptors. **Loratadine** is a **second-generation antihistamine**. These drugs are highly selective for peripheral H1 receptors and have poor CNS penetration due to their low lipid solubility and high affinity for P-glycoprotein efflux pumps. Consequently, they are "non-sedating" and lack significant anticholinergic side effects. **Analysis of Incorrect Options:** * **A. Promethazine:** A first-generation antihistamine known for its strong sedative and antiemetic properties. It is frequently used for motion sickness but carries a risk of respiratory depression. * **C. Diphenhydramine:** A classic first-generation antihistamine. It is highly lipid-soluble, crosses the BBB easily, and causes significant sedation and anticholinergic effects (dry mouth, urinary retention). * **D. Doxylamine:** A first-generation antihistamine often used as an over-the-counter sleep aid or in combination with Pyridoxine for morning sickness in pregnancy. **High-Yield Clinical Pearls for NEET-PG:** * **Active Metabolites:** Loratadine is a prodrug; its active metabolite is **Desloratadine**. Similarly, Terfenadine’s active metabolite is **Fexofenadine**. * **Safety Profile:** Second-generation drugs are preferred for pilots, drivers, and students because they do not impair psychomotor performance. * **Cardiac Warning:** Astemizole and Terfenadine (older 2nd gen) were withdrawn due to the risk of **QT interval prolongation** and *Torsades de Pointes* when co-administered with CYP3A4 inhibitors (e.g., Ketoconazole, Erythromycin). Fexofenadine and Loratadine do not carry this risk. * **Third Generation:** Some texts refer to active isomers or metabolites like Levocetirizine and Fexofenadine as "third-generation" due to even higher potency and fewer side effects.

Question 190: Pulmonary fibrosis occurs most commonly due to which of the following drugs?

A. Clindamycin
B. Amiodarone (Correct Answer)
C. Nikkomycin
D. Kanamycin

Explanation: **Explanation:** **Amiodarone** is a Class III antiarrhythmic drug known for its high iodine content and long half-life. **Pulmonary toxicity** is its most serious adverse effect, occurring in approximately 5–10% of patients. The underlying mechanism involves both direct cellular toxicity and an indirect inflammatory response (phospholipidosis), where lipids accumulate within alveolar macrophages. This leads to chronic interstitial inflammation and, ultimately, **irreversible pulmonary fibrosis**. Risk factors include a cumulative dose, older age, and pre-existing lung disease. **Analysis of Incorrect Options:** * **Clindamycin (A):** A lincosamide antibiotic primarily associated with gastrointestinal side effects, most notably *Clostridioides difficile*-associated pseudomembranous colitis. * **Nikkomycin (C):** An experimental antifungal agent that inhibits chitin synthesis; it is not associated with pulmonary fibrosis. * **Kanamycin (D):** An aminoglycoside antibiotic. Its primary toxicities are ototoxicity (vestibulocochlear nerve damage) and nephrotoxicity, not pulmonary fibrosis. **High-Yield Clinical Pearls for NEET-PG:** * **Other drugs causing Pulmonary Fibrosis:** Remember the mnemonic **"B-B-M-A-T"**: **B**leomycin (most common chemotherapy cause), **B**usulfan, **M**ethotrexate, **A**miodarone, and **T**oxic Nitrofurantoin. * **Monitoring:** Patients on chronic Amiodarone therapy require baseline and periodic **Chest X-rays** and **Pulmonary Function Tests (PFTs)**. * **Amiodarone Side Effects:** Think of "6 Ps": **P**ulmonary fibrosis, **P**rolonged QT, **P**hotodermatitis (Blue-gray skin), **P**eripheral neuropathy, **P**hotophobia (corneal microdeposits), and **P**erturbed thyroid (Hypo/Hyperthyroidism).

Practice by Chapter

Bronchodilators

Practice Questions

Corticosteroids in Respiratory Disorders

Practice Questions

Anti-inflammatory Respiratory Agents

Practice Questions

Mast Cell Stabilizers

Practice Questions

Leukotriene Modifiers

Practice Questions

Antitussives and Expectorants

Practice Questions

Nasal Decongestants

Practice Questions

Pulmonary Surfactants

Practice Questions

Drugs for Pulmonary Hypertension

Practice Questions

Oxygen Therapy

Practice Questions

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