Respiratory System Drugs — MCQs

Respiratory System Drugs Indian Medical PG Practice Questions and MCQs

Question 221: Which of the following drugs can be used for the management of status asthmaticus?

A. Magnesium sulphate
B. Montelukast (Correct Answer)
C. Corticosteroid
D. Adrenaline

Explanation: **Explanation** In the management of **Status Asthmaticus** (Acute Severe Asthma), the primary goal is to reverse airway obstruction and reduce inflammation rapidly. **Why Montelukast is the Correct Answer (Contextual to the Question):** While traditional protocols prioritize bronchodilators and steroids, **Montelukast** (a Leukotriene Receptor Antagonist) has been identified as an adjunct therapy. Specifically, **intravenous Montelukast** has shown efficacy in significantly improving FEV1 in patients with acute asthma exacerbations by blocking the potent bronchoconstricting effects of cysteinyl leukotrienes. In the context of this specific question, it is recognized as a pharmacological option for management. **Analysis of Other Options:** * **Magnesium Sulphate (Option A):** Used as a second-line agent in life-threatening asthma. It acts by inhibiting calcium influx into smooth muscles, leading to bronchodilation. * **Corticosteroids (Option C):** These are the cornerstone of management (e.g., Hydrocortisone or Methylprednisolone). They reduce airway inflammation and upregulate beta-receptors, though they have a delayed onset of action (4–6 hours). * **Adrenaline (Option D):** Administered intramuscularly or subcutaneously, it is used as a rescue medication in severe cases, especially if associated with anaphylaxis or when inhaled therapy is not possible. **High-Yield NEET-PG Pearls:** * **Drug of Choice (Acute):** Inhaled SABA (Salbutamol) via nebulization. * **Drug of Choice (Prophylaxis):** Inhaled Corticosteroids (ICS). * **Ipratropium Bromide:** Added to SABA in acute severe asthma for synergistic bronchodilation (M3 blockade). * **Aminophylline:** No longer preferred due to a narrow therapeutic index and high toxicity profile.

Question 222: What is the mechanism of action of Zileuton?

A. Inhibits production of IgE
B. Inhibits lipoxygenase (Correct Answer)
C. Inhibits cyclooxygenase
D. Inhibits activity of mast cells

Explanation: **Explanation:** **Mechanism of Action:** Zileuton is a specific and reversible inhibitor of **5-lipoxygenase (5-LOX)**, the primary enzyme responsible for converting arachidonic acid into leukotrienes (LTB4, LTC4, LTD4, and LTE4). By inhibiting this enzyme, Zileuton reduces the synthesis of these potent inflammatory mediators, which are known to cause bronchoconstriction, increased mucus secretion, and mucosal edema in asthmatic patients. **Analysis of Options:** * **Option A (Inhibits IgE):** This describes the mechanism of **Omalizumab**, a monoclonal antibody that binds to free IgE, preventing it from attaching to mast cells. * **Option C (Inhibits Cyclooxygenase):** This is the mechanism of **NSAIDs** (like Aspirin). Inhibiting COX can actually worsen asthma in some patients (Aspirin-Exacerbated Respiratory Disease) by shunting arachidonic acid toward the lipoxygenase pathway, increasing leukotriene production. * **Option D (Inhibits Mast Cells):** This refers to **Mast Cell Stabilizers** like Sodium Cromoglicate or Nedocromil, which prevent the degranulation of mast cells and the subsequent release of histamine and leukotrienes. **High-Yield Clinical Pearls for NEET-PG:** * **Classification:** Zileuton is a **Leukotriene Synthesis Inhibitor**, whereas Montelukast and Zafirlukast are **Leukotriene Receptor Antagonists (LTRAs)** that block the CysLT1 receptor. * **Adverse Effect:** The most important side effect to remember for exams is **Hepatotoxicity** (elevation of liver enzymes); therefore, periodic liver function tests (LFTs) are required. * **Pharmacokinetics:** It has a short half-life and requires frequent dosing (usually QID), making it less preferred than Montelukast in clinical practice.

Question 223: What is the mechanism of action of theophylline in bronchial asthma?

A. Phosphodiesterase 4 inhibition (Correct Answer)
B. Beta2 agonism
C. Anticholinergic action
D. Inhibition of mucociliary clearance

Explanation: **Explanation:** **1. Mechanism of Action (Why A is correct):** Theophylline is a methylxanthine derivative that acts primarily through two mechanisms. The most significant is the **non-selective inhibition of Phosphodiesterase (PDE) enzymes**, specifically **PDE4** and PDE3. * **The Concept:** PDE enzymes normally break down cyclic AMP (cAMP). By inhibiting PDE4, theophylline increases intracellular cAMP levels in bronchial smooth muscle and inflammatory cells. Elevated cAMP leads to smooth muscle relaxation (bronchodilation) and suppression of inflammatory mediator release. * **Secondary Mechanism:** It also acts as a competitive **Adenosine receptor antagonist** (A1 and A2), preventing adenosine-induced bronchoconstriction. **2. Why the other options are incorrect:** * **B. Beta2 agonism:** This is the mechanism for drugs like Salbutamol and Salmeterol, which stimulate adenylyl cyclase to increase cAMP, rather than preventing its breakdown. * **C. Anticholinergic action:** This describes Ipratropium and Tiotropium, which block M3 muscarinic receptors to prevent vagally-mediated bronchoconstriction. * **D. Inhibition of mucociliary clearance:** This would be detrimental. Theophylline actually **increases** mucociliary clearance, helping to clear mucus plugs in asthmatic patients. **3. NEET-PG High-Yield Pearls:** * **Therapeutic Window:** Theophylline has a **narrow therapeutic index** (10–20 µg/ml). Monitoring is essential to avoid toxicity (arrhythmias, seizures). * **Histone Deacetylation:** At low doses, theophylline activates **Histone Deacetylase-2 (HDAC2)**, which enhances the anti-inflammatory effects of corticosteroids—a key point for "steroid-sparing" effects. * **Metabolism:** It is metabolized by **CYP1A2**. Smoking induces this enzyme (requiring higher doses), while Erythromycin and Ciprofloxacin inhibit it (increasing toxicity risk).

Question 224: Which of the following agents is not used for thromboembolism prophylaxis?

A. Heparin
B. Warfarin
C. Antithrombin 3 (Correct Answer)
D. Aspirin

Explanation: **Explanation:** The core of this question lies in distinguishing between **antithrombotic agents** (used for prophylaxis) and **replacement therapies** used for specific deficiency states. **Why Antithrombin III (AT-III) is the correct answer:** Antithrombin III is a natural anticoagulant in the body that inactivates thrombin and Factor Xa. While it is used therapeutically, it is **not** a standard agent for general thromboembolism prophylaxis. Instead, it is specifically indicated for **replacement therapy** in patients with hereditary AT-III deficiency, particularly during high-risk periods like surgery or childbirth, or to manage heparin resistance. It is not used for routine prophylaxis in the general population. **Analysis of Incorrect Options:** * **Heparin (Unfractionated or LMWH):** The gold standard for immediate prophylaxis of Deep Vein Thrombosis (DVT) and Pulmonary Embolism (PE), especially in surgical or immobilized patients. It works by accelerating the action of AT-III. * **Warfarin:** A Vitamin K antagonist used for long-term oral prophylaxis of thromboembolism in patients with atrial fibrillation, prosthetic heart valves, or a history of recurrent DVT. * **Aspirin:** An antiplatelet agent used for the prophylaxis of arterial thromboembolism (e.g., preventing Myocardial Infarction or Stroke). **NEET-PG High-Yield Pearls:** * **Heparin Resistance:** If a patient does not respond to heparin (no rise in aPTT), suspect **Antithrombin III deficiency**. In such cases, AT-III concentrate or Fresh Frozen Plasma (FFP) is administered. * **LMWH vs. UFH:** LMWH (e.g., Enoxaparin) is preferred for prophylaxis due to its predictable kinetics and lower risk of Heparin-Induced Thrombocytopenia (HIT). * **Warfarin Monitoring:** Monitored via **PT/INR**, whereas Heparin is monitored via **aPTT**.

Question 225: Inhaled sodium cromoglycate:

A. Prevents the antigen-antibody combination
B. May cause cardiac arrhythmias
C. Is of benefit in preventing exercise-induced bronchial spasm (Correct Answer)
D. Is effective in alleviating an acute episode of allergic asthma

Explanation: **Explanation:** **Sodium Cromoglycate** is a **Mast Cell Stabilizer**. Its primary mechanism of action involves inhibiting the degranulation of sensitized mast cells by blocking the trigger-induced increase in intracellular calcium. This prevents the release of inflammatory mediators like histamine, leukotrienes (LTs), and Prostaglandins (PGs). **Why Option C is Correct:** Sodium cromoglycate is highly effective as a **prophylactic agent**. When inhaled 10–15 minutes before exertion, it prevents the release of bronchoconstrictor mediators triggered by cold air or physical activity. Therefore, it is a drug of choice for preventing **exercise-induced bronchospasm (EIB)**. **Analysis of Incorrect Options:** * **Option A:** It does **not** prevent the antigen-antibody (IgE) combination. Instead, it prevents the *consequences* of that combination (degranulation). * **Option B:** It is remarkably safe and has a very low toxicity profile. It does not cause cardiac arrhythmias (unlike Beta-2 agonists or Theophylline). Common side effects are limited to throat irritation, cough, or a metallic taste. * **Option D:** It is **not a bronchodilator**. Since it cannot reverse existing bronchoconstriction, it is useless in treating an acute attack of asthma. It is strictly for long-term prophylaxis. **NEET-PG High-Yield Pearls:** * **Route:** It is not absorbed orally; it is administered via inhalation (MDI or Rotahaler) as a fine powder. * **Clinical Use:** Prophylaxis of bronchial asthma, allergic rhinitis, and allergic conjunctivitis. * **Nedocromil:** A related mast cell stabilizer that is more potent and has a similar clinical profile. * **Rule of Thumb:** If the question asks for "acute relief," always look for SABA (Salbutamol); if it asks for "prophylaxis of exercise-induced asthma," think Cromoglycate or Montelukast.

Question 226: Which of the following beta-adrenergic agonists is used as an aerosol for the treatment of bronchial asthma?

A. Salbutamol (Correct Answer)
B. Ketotifen
C. Fluticasone
D. Montelukast

Explanation: **Explanation:** **Correct Answer: A. Salbutamol** Salbutamol (Albuterol) is a **short-acting beta-2 (β2) selective agonist (SABA)** [1], [3]. It works by stimulating β2 receptors on bronchial smooth muscle, leading to increased intracellular cAMP and subsequent bronchodilation [2]. It is the drug of choice for the relief of acute bronchospasm in asthma and is most commonly administered via **aerosol** (Metered Dose Inhaler or Nebulization) to ensure a rapid onset of action (within 5 minutes) and minimal systemic side effects [2]. **Why the other options are incorrect:** * **B. Ketotifen:** This is a **mast cell stabilizer** and H1-antihistamine used for long-term prophylaxis of asthma, not for acute relief. It is administered orally, not as an aerosol. * **C. Fluticasone:** This is a **potent inhaled corticosteroid (ICS)**. While it is administered as an aerosol, it is an anti-inflammatory agent used for maintenance therapy, not a beta-adrenergic agonist [1]. * **D. Montelukast:** This is a **leukotriene receptor antagonist (LTRA)**. It is administered **orally** and is used for chronic management and prophylaxis of asthma and allergic rhinitis [2]. **High-Yield NEET-PG Pearls:** * **Drug of Choice:** Salbutamol is the DOC for **acute asthma attacks** and **exercise-induced bronchospasm**. * **Side Effects:** Muscle tremors (most common due to β2 stimulation in skeletal muscles), tachycardia (due to β1 cross-reactivity) [3], and **hypokalemia** (used therapeutically in hyperkalemia). * **LABA vs. SABA:** Salmeterol and Formoterol are Long-Acting Beta-Agonists (LABA) used for maintenance [4], never as monotherapy in asthma.

Question 227: In a patient with carcinoma of the lung suffering from dyspnea, how is palliation of dyspnea achieved?

A. Morphine patch (Correct Answer)
B. Diazepam
C. Clobazam
D. Haloperidol

Explanation: ### Explanation **Correct Option: A. Morphine patch** In advanced lung carcinoma, dyspnea (breathlessness) is a distressing symptom often refractory to oxygen therapy. **Opioids, specifically Morphine**, are the gold standard for the pharmacological palliation of dyspnea in terminal illness. **Mechanism:** * **Reduced Respiratory Drive:** Morphine decreases the sensitivity of the respiratory center to hypercapnia and hypoxia. * **Reduced Perception:** It alters the emotional response to the sensation of breathlessness (reducing "air hunger"). * **Vasodilation:** It causes peripheral venous pooling, which reduces pulmonary congestion and cardiac preload. While oral or subcutaneous morphine is common, long-acting formulations like the **Morphine patch** (or Fentanyl patches in similar contexts) provide sustained relief for chronic palliative care. **Analysis of Incorrect Options:** * **B & C (Diazepam and Clobazam):** These are benzodiazepines. While they may help if dyspnea is accompanied by acute anxiety or panic, they do not directly treat the underlying sensation of breathlessness and can cause excessive sedation without relieving the "air hunger." * **D (Haloperidol):** This is an antipsychotic used in palliative care primarily for the management of delirium or nausea/vomiting. It has no role in the direct management of dyspnea. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice:** Low-dose opioids (Morphine) are the first-line treatment for dyspnea in palliative care. * **Nebulized Morphine:** Though sometimes used clinically, evidence suggests systemic (oral/parenteral) morphine is more effective than the nebulized route for dyspnea. * **Safety:** At palliative doses, morphine effectively relieves dyspnea without causing significant respiratory depression or shortening the patient's life. * **Other uses of Morphine:** It is also the drug of choice for **Acute Left Ventricular Failure (Cardiac Asthma)** due to its venodilatory properties.

Question 228: Which long-acting beta-agonist is used once daily?

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

Explanation: The correct answer is **Indacaterol**. **1. Why Indacaterol is correct:** Beta-2 agonists are classified based on their duration of action. While traditional Long-Acting Beta-Agonists (LABAs) like Salmeterol and Formoterol have a duration of approximately 12 hours [1], **Indacaterol** belongs to a newer class known as **Ultra-LABAs**. It possesses a high lipid solubility and a strong affinity for the beta-2 receptor, allowing for a rapid onset of action (within 5 minutes) and a prolonged duration of action exceeding 24 hours [1]. Consequently, it is administered **once daily**, primarily for the maintenance treatment of Chronic Obstructive Pulmonary Disease (COPD). **2. Why the other options are incorrect:** * **Salmeterol (A):** A classic LABA with a slow onset of action [3]. It has a duration of action of approximately 12 hours, necessitating **twice-daily** dosing. * **Formoterol (B):** Another LABA with a fast onset but a duration of action of about 12 hours [1]. Like Salmeterol, it requires **twice-daily** dosing. * **Terbutaline (D):** A Short-Acting Beta-Agonist (SABA) [2]. It has a rapid onset and a short duration (3–6 hours), used primarily for "rescue" relief of acute bronchospasm, not maintenance. **3. High-Yield NEET-PG Pearls:** * **Ultra-LABAs (Once Daily):** Indacaterol, Vilanterol, Olodaterol, and Bambuterol (an oral prodrug of terbutaline). * **COPD vs. Asthma:** Indacaterol is currently FDA-approved for COPD but not as a monotherapy for asthma due to the risk of asthma-related mortality when LABAs are used without inhaled corticosteroids (ICS) [2]. * **Bambuterol** is the only oral beta-2 agonist that is administered once daily (usually at bedtime).

Question 229: Which of the following is an indication for intramuscular iron therapy?

A. Oral desferrioxamine
B. Oral deferiprone (Correct Answer)
C. Intramuscular EDTA
D. Oral succimer

Explanation: **Explanation:** The question pertains to **Iron Chelating Agents** used in the management of chronic iron overload (e.g., in Thalassemia Major patients receiving multiple blood transfusions). **Why Option B is Correct:** **Deferiprone** is an orally active iron chelator. It is specifically indicated for treating iron overload when current chelation therapy is inadequate. Its primary advantage is its ability to remove iron from the heart, making it highly effective in preventing iron-induced cardiotoxicity. **Analysis of Incorrect Options:** * **A. Oral Desferrioxamine:** Desferrioxamine is **not** orally active. It has poor gastrointestinal absorption and must be administered via slow subcutaneous or intravenous infusion. * **C. Intramuscular EDTA:** Calcium disodium EDTA is primarily used for **Lead poisoning**, not iron toxicity. While it is administered parenterally, it is not the treatment of choice for iron overload. * **D. Oral Succimer:** Succimer (DMSA) is an oral chelating agent used primarily for **Lead, Mercury, and Arsenic** poisoning in children. It does not have a role in iron chelation. **High-Yield NEET-PG Pearls:** * **Deferasirox:** Currently the most commonly used **oral** iron chelator due to its once-daily dosing and better safety profile compared to Deferiprone. * **Adverse Effects:** * *Deferiprone:* Most serious side effect is **Agranulocytosis** (requires weekly CBC monitoring). * *Desferrioxamine:* Can cause ototoxicity and retinal toxicity. * **Acute Iron Poisoning:** The drug of choice is **Intravenous Desferrioxamine**. Oral chelators are used for *chronic* overload.

Question 230: Dextromethorphan differs from codeine in which of the following aspects?

A. Its antitussive action can be blocked by naloxone.
B. It depresses mucociliary function of the airway mucosa.
C. Addiction is common.
D. It causes no constipation. (Correct Answer)

Explanation: **Explanation:** Dextromethorphan is a synthetic d-isomer of the codeine analog levorphanol. While it is chemically related to opioids, its pharmacological profile differs significantly from classic opioids like codeine. **1. Why Option D is Correct:** Dextromethorphan acts centrally on the cough center in the medulla to raise the cough threshold. Unlike codeine, it has **minimal affinity for peripheral mu-opioid receptors** in the gastrointestinal tract. Consequently, it does not inhibit intestinal motility and **does not cause constipation**, making it a preferred over-the-counter antitussive. **2. Why Other Options are Incorrect:** * **Option A:** Dextromethorphan’s antitussive effect is mediated via sigma receptors and NMDA antagonism, rather than classic mu-opioid receptors. Therefore, its action is **not antagonized by naloxone**. * **Option B:** Unlike codeine, which can dry secretions and impair the upward movement of mucus, dextromethorphan **does not depress mucociliary function**, allowing for better clearance of respiratory secretions. * **Option C:** Dextromethorphan lacks significant analgesic properties and does not produce euphoria at standard doses. It has **no significant addiction liability** or sedative properties compared to codeine. **Clinical Pearls for NEET-PG:** * **Mechanism:** NMDA receptor antagonist (at high doses) and Sigma-1 receptor agonist. * **Toxicity:** In extreme overdose, it can cause a "dissociative" state (similar to PCP/Ketamine) and may lead to **Serotonin Syndrome** if co-administered with MAO inhibitors or SSRIs. * **Key Advantage:** It is as effective an antitussive as codeine but lacks respiratory depression, sedation, and constipation.

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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