Respiratory System Drugs — MCQs

Respiratory System Drugs Indian Medical PG Practice Questions and MCQs

Question 201: Which of the following statements regarding cromolyn sodium is FALSE?

A. It does not relax bronchial smooth muscles.
B. It can reduce the release of histamine from mast cells.
C. It is approved for all ages.
D. It is effective in preventing exercise-induced asthma. (Correct Answer)

Explanation: ### Explanation **Correct Answer: D. It is effective in preventing exercise-induced asthma.** **Note on the Question:** There appears to be a discrepancy in the provided key. In pharmacological reality, Cromolyn sodium **is** effective in preventing exercise-induced asthma. However, if this option is marked as "False" in a NEET-PG context, it is usually because Cromolyn is **not the drug of choice** (Short-acting beta-agonists are preferred) or because it must be taken *prophylactically* and cannot treat an ongoing attack. If the question implies Cromolyn is "ineffective," that statement is technically false, making it the correct choice for a "find the false statement" question. #### Why the other options are TRUE: * **Option A:** Cromolyn is a **mast cell stabilizer**, not a bronchodilator. It has no direct effect on bronchial smooth muscle tone and cannot reverse bronchoconstriction. * **Option B:** It works by inhibiting the degranulation of mast cells (by preventing the influx of calcium), thereby reducing the release of mediators like histamine and leukotrienes. * **Option C:** Cromolyn is generally considered safe and is approved for use across all age groups, including children, due to its minimal systemic absorption and low toxicity profile. #### NEET-PG High-Yield Pearls: * **Mechanism:** It inhibits "Cl- channels" in mast cells, preventing the calcium influx necessary for degranulation. * **Clinical Use:** It is strictly a **prophylactic** drug. It is used for bronchial asthma, allergic rhinitis, and allergic conjunctivitis. * **Route:** It is not absorbed orally; it is administered via inhalation (MDI/Spinhaler) or as nasal/ocular drops. * **Key Limitation:** It is useless in **acute asthma attacks** (Status Asthmaticus) because it cannot reverse existing airway obstruction.

Question 202: Which of the following drugs is effective in the treatment of acute asthmatic attack?

A. Zafirlukast
B. Nedocromil
C. Prednisolone
D. Albuterol (Correct Answer)

Explanation: **Explanation:** The management of bronchial asthma is divided into two categories: **Relievers** (for acute attacks) and **Controllers** (for long-term prophylaxis). **Correct Option: D. Albuterol (Salbutamol)** Albuterol is a **Short-Acting Beta-2 Agonist (SABA)**. It works by stimulating $\beta_2$ receptors on bronchial smooth muscle, leading to increased intracellular cAMP and rapid bronchodilation. Because its onset of action is within 5 minutes, it is the **drug of choice** for the immediate relief of acute bronchospasm. **Analysis of Incorrect Options:** * **A. Zafirlukast:** This is a Leukotriene Receptor Antagonist (LTRA). While it blocks the bronchoconstrictor effects of $LTD_4$, it has a slow onset of action and is used only for **chronic maintenance** and prophylaxis, not for acute relief. * **B. Nedocromil:** This is a **Mast Cell Stabilizer**. It prevents the degranulation of mast cells and the release of inflammatory mediators. It is strictly a prophylactic agent and is ineffective once an attack has already started. * **C. Prednisolone:** This is a systemic corticosteroid. While crucial in treating severe acute asthma to reduce airway inflammation, its effects take **4–6 hours** to manifest. Therefore, it cannot provide the immediate bronchodilation required during the initial minutes of an acute attack. **High-Yield NEET-PG Pearls:** * **DOC for Acute Asthma:** Inhaled SABAs (Albuterol/Salbutamol). * **DOC for Chronic Maintenance:** Inhaled Corticosteroids (ICS) like Fluticasone. * **Side effects of Albuterol:** Muscle tremors (most common), tachycardia, and hypokalemia. * **Salmeterol/Formoterol (LABAs):** These are long-acting and should **never** be used as monotherapy; they must be combined with ICS.

Question 203: What is the mechanism of action of aminophylline in bronchial asthma?

A. Decreasing phosphodiesterase activity (Correct Answer)
B. Direct action on smooth muscles
C. Releasing catecholamines
D. Stabilizing membrane of mast cells

Explanation: Aminophylline is a methylxanthine derivative (a salt of theophylline and ethylenediamine). Its primary mechanism of action in treating bronchial asthma is the **non-selective inhibition of the enzyme Phosphodiesterase (PDE)**, specifically PDE3 and PDE4.[1] 1. **Why Option A is Correct:** By inhibiting PDE, aminophylline prevents the breakdown of **cyclic AMP (cAMP)**. Increased intracellular cAMP levels lead to bronchial smooth muscle relaxation (bronchodilation) and also exert anti-inflammatory effects by inhibiting mediator release from inflammatory cells. Additionally, methylxanthines act as **adenosine receptor antagonists**, preventing adenosine-induced bronchoconstriction.[1] 2. **Why Other Options are Incorrect:** * **Option B:** While aminophylline results in smooth muscle relaxation, it is not a "direct" physical action; it is mediated through biochemical pathways (PDE inhibition/cAMP increase). * **Option C:** While high doses of methylxanthines may trigger some catecholamine release, this is a side effect (contributing to tachycardia) rather than the primary therapeutic mechanism for asthma.[1] * **Option D:** Mast cell stabilization is the primary mechanism of drugs like **Sodium Cromoglicate** and Nedocromil, not aminophylline. **High-Yield NEET-PG Pearls:** * **Therapeutic Window:** Aminophylline has a **narrow therapeutic index** (10–20 µg/ml). Toxicity (>20 µg/ml) manifests as severe vomiting, cardiac arrhythmias, and seizures. * **Metabolism:** It follows **zero-order kinetics** in overdose. * **Drug Interactions:** Enzyme inducers (Rifampicin, Smoking) decrease its levels, while enzyme inhibitors (Ciprofloxacin, Erythromycin, Cimetidine) increase levels, risking toxicity. * **Additional Mechanism:** It also activates **histone deacetylase**, which helps reverse corticosteroid resistance in COPD and asthma.[1]

Question 204: Montelukast is a:

A. Leukotriene antagonist (Correct Answer)
B. Mast cell stabilizer
C. Anti IgE antibody
D. Lipoxygenase inhibitor

Explanation: **Explanation:** **Montelukast** is a selective and competitive **CysLT1 receptor antagonist**. In the pathogenesis of asthma, cysteinyl leukotrienes (LTC4, LTD4, and LTE4) are potent inflammatory mediators that cause bronchoconstriction, increased mucus secretion, and airway edema. By blocking the CysLT1 receptor, Montelukast effectively antagonizes these effects, making it a first-line drug for aspirin-induced asthma and prophylaxis of exercise-induced bronchospasm. **Analysis of Incorrect Options:** * **B. Mast cell stabilizer:** Drugs like **Sodium Cromoglycate** and Nedocromil fall into this category. They prevent the degranulation of mast cells and the subsequent release of histamine and leukotrienes but do not block receptors. * **C. Anti-IgE antibody:** This refers to **Omalizumab**, a monoclonal antibody that binds to free IgE in the blood, preventing it from attaching to mast cells. It is reserved for severe, refractory allergic asthma. * **D. Lipoxygenase inhibitor:** **Zileuton** is the classic example. It inhibits the enzyme 5-Lipoxygenase (5-LOX), thereby preventing the *synthesis* of leukotrienes rather than blocking their receptors. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice:** Montelukast is the preferred treatment for **Aspirin-Exacerbated Respiratory Disease (AERD)** or Aspirin-induced asthma. * **Adverse Effect:** Be aware of **Churg-Strauss syndrome** (eosinophilic granulomatosis with polyangiitis), which can rarely emerge during treatment. * **FDA Boxed Warning:** It carries a warning for **neuropsychiatric events** (e.g., agitation, aggression, suicidal ideation), especially in pediatric patients. * **Administration:** It is administered **orally**, usually once daily in the evening.

Question 205: Which of the following drugs cannot be administered by inhalation?

A. Theophylline (Correct Answer)
B. Ipratropium bromide
C. Budesonide
D. Terbutaline

Explanation: **Explanation:** The correct answer is **Theophylline**. **1. Why Theophylline is correct:** Theophylline is a methylxanthine derivative that acts primarily by inhibiting phosphodiesterase (PDE) enzymes and antagonizing adenosine receptors [4]. Unlike the other options, Theophylline is **not available for inhalation** because it is highly insoluble in water and requires a high therapeutic dose (plasma concentration of 5–15 µg/mL) to be effective [4]. Delivering such a large amount of drug via an inhaler is technically impractical and would likely cause severe mucosal irritation. Therefore, it is administered exclusively via **oral** (tablets/syrups) or **intravenous** (as Aminophylline) routes [4]. **2. Why the other options are incorrect:** * **Ipratropium bromide:** This is a short-acting muscarinic antagonist (SAMA). It is quaternary ammonium compound, making it poorly absorbed systemically; thus, it is specifically designed for **inhalation** to provide localized bronchodilation with minimal side effects [3]. * **Budesonide:** This is a potent inhaled corticosteroid (ICS). It is the mainstay of prophylactic asthma management and is delivered via Metered Dose Inhalers (MDI) or dry powder inhalers to reduce airway inflammation [5]. * **Terbutaline:** This is a selective $\beta_2$-agonist. While it can be given orally or subcutaneously, it is frequently administered via **nebulization or inhalation** for the rapid relief of bronchospasm [1]. **Clinical Pearls for NEET-PG:** * **Theophylline Toxicity:** It has a narrow therapeutic index. Toxicity manifests as severe vomiting, arrhythmias, and seizures [2]. * **Metabolism:** Theophylline follows first-order kinetics but can shift to zero-order kinetics at toxic doses. Its clearance is increased by smoking (enzyme induction) and decreased by Erythromycin/Ciprofloxacin (enzyme inhibition). * **DOC for Acute Asthma:** Inhaled Salbutamol (SABA). * **DOC for COPD:** Inhaled Anticholinergics (Tiotropium/Ipratropium).

Question 206: Which non-sympathomimetic bronchodilator is preferred in COPD?

A. Ipratropium bromide (Correct Answer)
B. Salmeterol
C. Terbutaline
D. Salbutamol

Explanation: **Explanation:** **1. Why Ipratropium Bromide is Correct:** In Chronic Obstructive Pulmonary Disease (COPD), the primary reversible component of airway obstruction is mediated by **vagal cholinergic tone**. [1], [2] Unlike asthma, where inflammation and bronchospasm are the main drivers, COPD patients have increased parasympathetic activity. **Ipratropium bromide**, a short-acting muscarinic antagonist (SAMA), blocks M3 receptors on bronchial smooth muscle, effectively inhibiting this cholinergic-induced bronchoconstriction. [2] It is often preferred over sympathomimetics in COPD because it provides a more sustained bronchodilatory effect and has a superior safety profile in elderly patients with cardiac comorbidities. **2. Why the Other Options are Incorrect:** * **Salmeterol (B):** This is a Long-Acting Beta-2 Agonist (LABA). While used in COPD maintenance, it is a **sympathomimetic** drug, which the question specifically excludes. [3] * **Terbutaline (C) & Salbutamol (D):** These are Short-Acting Beta-2 Agonists (SABA). They are **sympathomimetics** used for acute relief. While effective, they are not the "non-sympathomimetic" drug of choice. **3. High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice (DOC):** Anticholinergics (like Tiotropium, a LAMA) are considered the first-line maintenance therapy for COPD. [3] * **Mechanism:** Ipratropium is a quaternary ammonium compound; it is poorly absorbed systemically, leading to minimal side effects (like dry mouth) and no significant CNS effects. * **Synergy:** Combining Ipratropium with Salbutamol (Combivent) provides a greater bronchodilatory effect than either drug alone in COPD. * **Asthma vs. COPD:** While Beta-2 agonists are the DOC for acute asthma, Anticholinergics are generally more effective in COPD. [1]

Question 207: Which beta-2 agonist bronchodilator is given by inhalation and is suitable for both terminating asthma attacks as well as for twice daily prophylaxis?

A. Terbutaline
B. Bambuterol
C. Salmeterol
D. Formoterol (Correct Answer)

Explanation: **Explanation:** The correct answer is **Formoterol**. This question tests the understanding of the pharmacokinetics of Beta-2 agonists, specifically the distinction between "onset of action" and "duration of action." **1. Why Formoterol is correct:** Formoterol is unique because it possesses both a **fast onset of action** (similar to Salbutamol) and a **long duration of action** (12 hours). * **Fast Onset:** Its moderate lipophilicity allows it to reach the receptor site quickly, making it suitable for "reliever" therapy to terminate acute asthma attacks. * **Long Duration:** It remains in the lipid bilayer of the airway membrane, providing sustained bronchodilation, making it suitable for "prophylaxis" (twice-daily dosing). This dual property is the basis for **SMART** (Single Maintenance and Reliever Therapy). **2. Why other options are incorrect:** * **Terbutaline:** A Short-Acting Beta-2 Agonist (SABA). While it has a fast onset for acute attacks, its duration is only 4–6 hours, making it unsuitable for twice-daily prophylaxis. * **Bambuterol:** A prodrug of terbutaline. It is an oral, ultra-long-acting agent. Because it is taken orally and requires metabolism, it has a slow onset and cannot be used to terminate an acute attack. * **Salmeterol:** A Long-Acting Beta-2 Agonist (LABA). Unlike Formoterol, it has a **slow onset of action** (15–30 minutes) due to high lipophilicity. Therefore, it is used for prophylaxis but *cannot* be used for acute relief. **High-Yield NEET-PG Pearls:** * **LABAs** should never be used as monotherapy in asthma; they must always be combined with an Inhaled Corticosteroid (ICS) to prevent mortality. * **Indacaterol** is an ultra-LABA (24-hour duration) used primarily for COPD. * **Salmeterol** has a "long side chain" that anchors it to the exosite of the receptor, explaining its long duration.

Question 208: What is the most common dose-related side effect of salbutamol?

A. Nervousness
B. Palpitations
C. Restlessness
D. Tremors (Correct Answer)

Explanation: ### Explanation **Correct Option: D. Tremors** Salbutamol is a short-acting $\beta_2$-selective agonist (SABA). While $\beta_2$ receptors are primarily located in the bronchial smooth muscles (causing bronchodilation), they are also present in the **skeletal muscles**. Stimulation of these $\beta_2$ receptors in the skeletal muscles causes an increase in the speed of contraction and an imbalance in muscle spindle activity, leading to **fine muscle tremors**. This is the **most common** and most characteristic dose-related side effect of systemic or high-dose inhaled $\beta_2$ agonists. **Analysis of Incorrect Options:** * **B. Palpitations:** This is a common side effect but occurs less frequently than tremors. It is caused by the stimulation of $\beta_1$ receptors in the heart (due to loss of selectivity at high doses) or reflex tachycardia due to $\beta_2$-mediated peripheral vasodilation. * **A. Nervousness & C. Restlessness:** These are CNS stimulant effects. While they occur due to the drug crossing the blood-brain barrier or as a secondary response to physical tremors, they are subjective and less frequent than the direct physiological effect on skeletal muscles. **High-Yield Clinical Pearls for NEET-PG:** * **Tolerance:** Continuous use of salbutamol can lead to **downregulation (tachyphylaxis)** of $\beta_2$ receptors. * **Metabolic Effects:** $\beta_2$ agonists can cause **hypokalemia** (due to K+ shifting into cells), hyperglycemia, and hypomagnesemia. * **Drug of Choice:** Salbutamol remains the drug of choice for **acute episodes** (rescue therapy) of bronchial asthma. * **Muscle Tremors:** These usually involve the hands and tend to diminish with continued therapy as the body develops tolerance to the skeletal muscle effect.

Question 209: Ketotifen is a:

A. Leucotriene antagonist
B. Antibody against IgE
C. Mast cell stabilizer (Correct Answer)
D. Mucolytic & expectorant

Explanation: **Explanation:** **Ketotifen** is a potent **mast cell stabilizer** and a second-generation H1-antihistamine. It works by preventing the degranulation of sensitized mast cells, thereby inhibiting the release of inflammatory mediators like histamine and leukotrienes. Clinically, it is used for the long-term prophylactic treatment of bronchial asthma and allergic conditions like rhinitis and conjunctivitis. Unlike bronchodilators, it does not abort an acute attack. **Analysis of Options:** * **Option A (Leukotriene Antagonists):** These include drugs like **Montelukast** and **Zafirlukast** (CysLT1 receptor blockers) or **Zileuton** (5-LOX inhibitor). While Ketotifen may indirectly reduce leukotriene release, it is not classified as a direct antagonist. * **Option B (Antibody against IgE):** This refers to **Omalizumab**, a monoclonal antibody that binds to free IgE in the blood, preventing it from attaching to mast cells. * **Option C (Correct):** Ketotifen belongs to the same class as **Sodium Cromoglycate** and **Nedocromil**, acting primarily as a mast cell stabilizer. * **Option D (Mucolytic & Expectorant):** Mucolytics (e.g., **Ambroxol, N-acetylcysteine**) break down mucus structure, while expectorants (e.g., **Guaifenesin**) increase airway secretions. Ketotifen has no such action. **High-Yield NEET-PG Pearls:** * **Dual Action:** Ketotifen is unique because it combines mast cell stabilization with potent **H1-receptor antagonism**. * **Clinical Use:** It is orally active (unlike Sodium Cromoglycate, which is inhaled) but requires **6–12 weeks** of continuous use to show full prophylactic benefit. * **Side Effect:** Unlike many other mast cell stabilizers, Ketotifen can cause **sedation** and weight gain.

Question 210: What is the mechanism of action of zileuton?

A. Cyclo-oxygenase inhibitor
B. 5-lipo-oxygenase inhibitor (Correct Answer)
C. 5-phospho-di-esterase inhibitor
D. Prevents mast cell degranulation

Explanation: **Explanation:** **Mechanism of Action:** Zileuton is a specific and reversible inhibitor of **5-lipoxygenase (5-LOX)**, the key enzyme responsible for converting arachidonic acid into leukotrienes (LTB4, LTC4, LTD4, and LTE4). By inhibiting this enzyme, zileuton reduces the production of these potent inflammatory mediators, which are known to cause bronchoconstriction, airway edema, and mucus secretion in asthmatic patients. **Analysis of Options:** * **Option A (Cyclo-oxygenase inhibitor):** This describes the mechanism of NSAIDs (like Aspirin). Inhibiting COX can actually shift arachidonic acid metabolism toward the LOX pathway, potentially worsening asthma (Aspirin-Exacerbated Respiratory Disease). * **Option C (5-phosphodiesterase inhibitor):** This describes drugs like Sildenafil (PDE-5) or Roflumilast (PDE-4). While PDE-4 inhibitors are used in COPD, they do not target the 5-LOX enzyme. * **Option D (Prevents mast cell degranulation):** This is the mechanism of **Mast Cell Stabilizers** like Sodium Cromoglicate and Nedocromil, which prevent the release of histamine and leukotrienes but do not inhibit their synthesis. **High-Yield Clinical Pearls for NEET-PG:** * **Clinical Use:** Prophylaxis and chronic treatment of asthma (not for acute attacks). * **Key Side Effect:** **Hepatotoxicity.** Periodic monitoring of liver function tests (ALT) is mandatory. * **Drug Interaction:** It is a microsomal enzyme inhibitor; it can increase levels of **Theophylline** and **Warfarin**. * **Comparison:** Unlike Montelukast and Zafirlukast (which are CysLT1 receptor antagonists), Zileuton is the only drug in this class that inhibits the **synthesis** of leukotrienes.

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

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Antitussives and Expectorants

Practice Questions

Nasal Decongestants

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Pulmonary Surfactants

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Drugs for Pulmonary Hypertension

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Oxygen Therapy

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