Respiratory System Drugs — MCQs

Respiratory System Drugs Indian Medical PG Practice Questions and MCQs

Question 61: Which of the following drugs can be given inhalationally for the diagnosis of bronchial hyperactivity in patients who do not have clinically apparent asthma?

A. Methacholine (Correct Answer)
B. Bethanechol
C. Pilocarpine
D. All of the above

Explanation: **Explanation:** The correct answer is **Methacholine**. This drug is used in the **Methacholine Challenge Test (Bronchial Provocation Test)** to diagnose bronchial hyperreactivity in patients with atypical symptoms (like chronic cough) who have normal baseline spirometry. **1. Why Methacholine is correct:** Methacholine is a synthetic choline ester and a non-selective **muscarinic receptor agonist**. When inhaled, it acts directly on the M3 receptors in the bronchial smooth muscle, causing bronchoconstriction. In patients with asthma, the airways are hypersensitive; they will experience a significant drop in lung function (FEV1) at much lower doses of methacholine compared to healthy individuals. It is preferred because it has a longer duration of action than acetylcholine but is still rapidly degraded by acetylcholinesterase, making the test controlled and reversible. **2. Why other options are incorrect:** * **Bethanechol:** This is a quaternary ammonium compound with strong muscarinic activity but is primarily **selective for the GI tract and urinary bladder**. It is used for post-operative urinary retention and has negligible effects on the respiratory system. * **Pilocarpine:** This is a natural alkaloid used primarily in ophthalmology (for glaucoma) and to treat xerostomia (dry mouth). It is not used for bronchial provocation due to its systemic side effect profile and lack of standardized dosing for inhalation. **High-Yield Clinical Pearls for NEET-PG:** * **Diagnostic Criteria:** A positive test is defined as a **20% or greater decrease in FEV1** (PC20) following the inhalation of methacholine. * **Contraindications:** The test should not be performed in patients with severe airflow obstruction (baseline FEV1 <60%), recent myocardial infarction, or uncontrolled hypertension. * **Antidote:** If severe bronchospasm occurs during the test, a **short-acting beta-2 agonist (SABA)** like Salbutamol is administered immediately to reverse the effects.

Question 62: Iloprost in Pulmonary Arterial Hypertension is administered by which route?

A. Intravenous
B. Intramuscular
C. Oral
D. Inhalation (Correct Answer)

Explanation: **Explanation:** **Iloprost** is a synthetic analog of **Prostacyclin (PGI2)**. In the management of Pulmonary Arterial Hypertension (PAH), it acts as a potent pulmonary vasodilator and inhibitor of platelet aggregation. **Why Inhalation is the Correct Route:** The preferred route for Iloprost in PAH is **inhalation** via a nebulizer. This targeted delivery allows the drug to reach the pulmonary vasculature directly, causing localized vasodilation. This "selective" pulmonary effect minimizes systemic side effects (like systemic hypotension) and improves ventilation-perfusion (V/Q) matching by vasodilating only the well-ventilated areas of the lung. **Analysis of Incorrect Options:** * **Intravenous (A):** While other prostacyclins like **Epoprostenol** are primarily given via continuous IV infusion, Iloprost is specifically designed for inhalation to reduce the risks associated with permanent indwelling catheters (e.g., sepsis, thrombosis). * **Intramuscular (B):** This route is not used for prostacyclins due to unpredictable absorption and the risk of local pain/tissue irritation. * **Oral (C):** While an oral formulation of Iloprost exists in some countries, it is not the standard or most effective route for PAH compared to inhalation. **Selexipag** and **Beraprost** are the more common oral prostacyclin-pathway agents. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism:** Increases cAMP in vascular smooth muscle cells leading to vasodilation. * **Half-life:** Iloprost has a very short half-life (approx. 20–30 mins), requiring frequent dosing (6–9 inhalations per day). * **Side Effects:** Common side effects include cough, flushing, headache, and jaw pain. * **Drug of Choice:** For PAH, **Bosentan** (Endothelin antagonist) or **Sildenafil** (PDE-5 inhibitor) are often first-line, while prostacyclins are added in advanced stages (WHO Class III/IV).

Question 63: Which of the following conditions is treated with Ipratropium bromide?

A. Renal colic
B. Organophosphorus poisoning
C. Bronchial asthma (Correct Answer)
D. Miosis

Explanation: **Ipratropium bromide** is a quaternary ammonium compound that acts as a **short-acting muscarinic antagonist (SAMA)** [1]. It works by competitively blocking M3 receptors on the bronchial smooth muscles, leading to bronchodilation and a reduction in mucus secretion [1].**Why Option C is correct:**In **Bronchial Asthma** and COPD, parasympathetic (vagal) activity causes bronchoconstriction. Ipratropium inhibits this vagal tone [1, 2]. It is particularly useful in acute asthma exacerbations (combined with Salbutamol) and in patients who cannot tolerate Beta-2 agonists [1, 2]. Because it is a quaternary amine, it is poorly absorbed into the systemic circulation when inhaled, ensuring localized action in the lungs with minimal systemic side effects [1].**Why other options are incorrect:** * **A. Renal colic:** This is typically treated with antispasmodics (like Hyoscine or Dicyclomine) and NSAIDs. Ipratropium lacks the systemic distribution required to affect ureteral smooth muscle.* **B. Organophosphorus (OP) poisoning:** The drug of choice is **Atropine** (a tertiary amine) because it can cross the blood-brain barrier to antagonize central cholinergic effects. Ipratropium does not cross the BBB.* **D. Miosis:** Miosis (pupillary constriction) is treated with mydriatics like Atropine or Phenylephrine. Ipratropium is administered via inhalation and does not reach the eye unless accidentally sprayed directly into it.**High-Yield Clinical Pearls for NEET-PG:** * **Tiotropium** is a **LAMA** (Long-acting muscarinic antagonist) with a once-daily dosing schedule, preferred for maintenance therapy in COPD.* Ipratropium is the **drug of choice for bronchospasm induced by Beta-blockers**.* Unlike Atropine, Ipratropium **does not significantly impair mucociliary clearance**, making it safer for respiratory conditions.

Question 64: Ipratropium bromide, used in bronchial asthma, is classified as which of the following?

A. Sympathomimetics
B. Methylxanthines
C. Anticholinergics (Correct Answer)
D. Mast cell stabilizers

Explanation: **Explanation:** **Ipratropium bromide** is a quaternary ammonium derivative of atropine. It acts as a **competitive antagonist at muscarinic receptors (M3)** located on bronchial smooth muscle. By blocking the action of acetylcholine released from parasympathetic nerve endings, it inhibits bronchoconstriction and reduces mucus secretion, leading to bronchodilation. **Analysis of Options:** * **A. Sympathomimetics:** These drugs (e.g., Salbutamol, Formoterol) stimulate $\beta_2$-adrenergic receptors to increase cAMP, causing bronchodilation. Ipratropium does not act on adrenergic receptors. * **B. Methylxanthines:** This class (e.g., Theophylline) works by inhibiting phosphodiesterase (PDE) enzymes and antagonizing adenosine receptors. * **D. Mast cell stabilizers:** Drugs like Sodium Cromoglycate prevent the degranulation of mast cells and the release of inflammatory mediators; they do not have direct bronchodilatory properties. **NEET-PG High-Yield Pearls:** 1. **Drug of Choice:** Ipratropium/Tiotropium are the **drugs of choice for COPD**. In bronchial asthma, they are typically used as add-on therapy to $\beta_2$-agonists (SABA). 2. **Pharmacokinetics:** Being a quaternary ammonium compound, Ipratropium is highly polar. It is poorly absorbed into the systemic circulation when inhaled, resulting in **minimal systemic side effects** (like tachycardia or urinary retention). 3. **Tiotropium vs. Ipratropium:** Tiotropium is long-acting (LAMA) due to slow dissociation from M3 receptors, allowing for once-daily dosing, whereas Ipratropium is short-acting (SAMA). 4. **Clinical Advantage:** Unlike atropine, Ipratropium does not significantly impair mucociliary clearance.

Question 65: What is the indication for Reslizumab?

A. Ulcerative colitis
B. Multiple sclerosis
C. Bronchial asthma (Correct Answer)
D. Alzheimer's disease

Explanation: **Explanation:** **Reslizumab** is a humanized monoclonal antibody that targets **Interleukin-5 (IL-5)**. IL-5 is the major cytokine responsible for the growth, differentiation, recruitment, and activation of eosinophils. By binding to IL-5, Reslizumab prevents it from binding to its receptor on the surface of eosinophils, thereby reducing eosinophilic inflammation in the airways. **1. Why Bronchial Asthma is Correct:** Reslizumab is specifically indicated as an add-on maintenance treatment for patients with **severe eosinophilic asthma** (aged 18 years and older) whose symptoms are not adequately controlled with standard therapies like high-dose inhaled corticosteroids. **2. Why the other options are incorrect:** * **Ulcerative Colitis:** This condition is typically managed with anti-TNF agents (Infliximab), anti-integrins (Vedolizumab), or IL-12/23 inhibitors (Ustekinumab), not IL-5 inhibitors. * **Multiple Sclerosis:** Treatment involves disease-modifying therapies like Interferon-beta, Glatiramer acetate, or monoclonal antibodies like Natalizumab (anti-VLA4) and Ocrelizumab (anti-CD20). * **Alzheimer’s Disease:** Management focuses on cholinesterase inhibitors (Donepezil) and NMDA antagonists (Memantine). Newer monoclonal antibodies like Aducanumab target amyloid-beta plaques. **High-Yield Clinical Pearls for NEET-PG:** * **IL-5 Inhibitors:** Remember the trio—**Reslizumab, Mepolizumab** (both target IL-5 ligand), and **Benralizumab** (targets 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 biological for asthma that targets **IgE** rather than IL-5.

Question 66: Which of the following is a long-acting M3 antagonist used for bronchial asthma?

A. Ipratropium
B. Glycopyrolate
C. Cromoglycate
D. Tiotropium (Correct Answer)

Explanation: **Explanation** **Tiotropium** is the correct answer because it is a **Long-Acting Muscarinic Antagonist (LAMA)**. It works by blocking M3 receptors on bronchial smooth muscle, leading to bronchodilation. Its clinical superiority lies in its kinetic selectivity: it dissociates very slowly from M3 and M1 receptors but rapidly from M2 receptors (which are pre-junctional autoreceptors that inhibit acetylcholine release). This results in a prolonged duration of action (over 24 hours), allowing for once-daily dosing via inhalation. **Analysis of Incorrect Options:** * **A. Ipratropium:** This is a **Short-Acting Muscarinic Antagonist (SAMA)**. It has a rapid onset but a short duration of action (4–6 hours), requiring frequent dosing. It is primarily used for acute relief or in COPD exacerbations. * **B. Glycopyrrolate:** While it is an anticholinergic, it is traditionally used as a pre-anesthetic medication to reduce secretions or to reverse neuromuscular blockade. Though newer inhaled formulations exist for COPD, Tiotropium remains the classic prototype for long-acting asthma/COPD management in exams. * **C. Cromoglycate:** This is a **Mast Cell Stabilizer**, not an anticholinergic. It prevents the release of inflammatory mediators but does not cause direct bronchodilation. **High-Yield Pearls for NEET-PG:** * **Drug of Choice:** LAMAs like Tiotropium are the drugs of choice for **COPD** maintenance. * **Side Effects:** The most common side effect of inhaled anticholinergics is **dry mouth** (xerostomia). * **Safety:** Unlike beta-2 agonists, anticholinergics do not cause skeletal muscle tremors or cardiac arrhythmias, making them safer in elderly patients with comorbidities. * **Mnemonic:** Remember **"Tio"** (Tiotropium) stays **"Longer"** than **"Ipra"** (Ipratropium).

Question 67: Which statement is not true regarding beclomethasone?

A. Indicated for chronic use
B. An inhalational corticosteroid
C. Effective in acute asthma (Correct Answer)
D. Predisposes to fungal infections

Explanation: **Explanation:** Beclomethasone dipropionate is a potent **Inhaled Corticosteroid (ICS)** used as a first-line "controller" medication in the long-term management of bronchial asthma [4]. **Why Option C is the correct answer (False statement):** Corticosteroids, including beclomethasone, do not possess direct bronchodilatory properties [1], [2]. Their mechanism involves the modulation of gene expression (genomic effect) to reduce airway inflammation [2], which takes **hours to days** to manifest clinically [1]. Therefore, they are **ineffective in acute asthma attacks** (status asthmaticus), where rapid-acting bronchodilators like Salbutamol (SABA) are required [3]. **Analysis of other options:** * **Option A (True):** It is indicated for chronic use to reduce airway hyperreactivity and prevent exacerbations [1], [4]. * **Option B (True):** Beclomethasone is a classic example of an inhalational corticosteroid, designed to deliver high local concentrations to the lungs with minimal systemic absorption. * **Option D (True):** Local deposition of the drug in the oropharynx can suppress local immunity, predisposing patients to **Oropharyngeal Candidiasis** (Oral thrush) and hoarseness of voice (dysphonia). **High-Yield NEET-PG Pearls:** * **Prevention of Side Effects:** Patients should be advised to **rinse their mouth with water** and spit after each use to prevent fungal infections. * **Prodrug Status:** Beclomethasone dipropionate is a **prodrug** converted by esterases in the lungs to the active metabolite, beclomethasone-17-monopropionate. * **Ciclesonide:** Another ICS prodrug, often preferred because it is activated specifically by bronchial esterases, further reducing the risk of oral thrush.

Question 68: Which of the following inhaled gases is used to decrease pulmonary artery pressure in adults and infants?

A. Nitrous oxide
B. Nitrogen dioxide
C. Nitric oxide (Correct Answer)
D. Nitrogen

Explanation: ### Explanation **Correct Answer: C. Nitric Oxide (NO)** **Mechanism of Action:** Inhaled Nitric Oxide (iNO) is a potent, selective **pulmonary vasodilator**. When inhaled, it diffuses across the alveolar-capillary membrane into the vascular smooth muscle cells. It activates the enzyme **guanylyl cyclase**, increasing levels of cyclic guanosine monophosphate (**cGMP**). This leads to dephosphorylation of myosin light chains, causing smooth muscle relaxation and a rapid decrease in pulmonary artery pressure (PAP). **Why it is selective:** NO is rapidly inactivated by binding to hemoglobin (forming methemoglobin) once it enters the systemic circulation. Therefore, it causes vasodilation *only* in the lungs without causing systemic hypotension, making it the gold standard for treating **Persistent Pulmonary Hypertension of the Newborn (PPHN)** and acute pulmonary hypertension in adults (e.g., post-cardiac surgery). --- ### Why the other options are incorrect: * **A. Nitrous oxide (N₂O):** Known as "laughing gas," this is an inhalational anesthetic. It does not lower pulmonary pressure; in fact, it may mildly *increase* pulmonary vascular resistance. * **B. Nitrogen dioxide (NO₂):** This is a toxic gas and a common air pollutant. It causes significant airway inflammation and pulmonary edema rather than vasodilation. * **D. Nitrogen (N₂):** An inert gas that makes up 78% of the atmosphere. It has no specific pharmacological effect on vascular tone. --- ### NEET-PG High-Yield Pearls: * **Clinical Use:** Used in PPHN to improve oxygenation and reduce the need for ECMO (Extracorporeal Membrane Oxygenation). * **Diagnostic Use:** Used in the cardiac catheterization lab for **Vasoreactivity Testing** to identify patients with Primary Pulmonary Hypertension who might respond to Calcium Channel Blockers (CCBs). * **Toxicity Watch:** Monitor for **Methemoglobinemia** and rebound pulmonary hypertension upon abrupt withdrawal. * **Alternative:** Inhaled **Prostacyclin (Epoprostenol)** can also be used for similar indications.

Question 69: Inhibition of 5-lipoxygenase is useful in which of the following conditions?

A. Cardiac failure
B. Bronchial asthma (Correct Answer)
C. Hepatic failure
D. Arthritis

Explanation: **Explanation:** The correct answer is **Bronchial asthma**. **Mechanism of Action:** The enzyme **5-lipoxygenase (5-LOX)** is responsible for the conversion of arachidonic acid into **leukotrienes** (LTC4, LTD4, and LTE4). These cysteinyl leukotrienes are potent bronchoconstrictors, increase vascular permeability (causing mucosal edema), and promote mucus secretion. By inhibiting 5-LOX, the drug **Zileuton** prevents the synthesis of these mediators, thereby reducing airway inflammation and bronchospasm in patients with asthma. **Analysis of Incorrect Options:** * **Cardiac failure:** Treatment focuses on reducing preload/afterload (ACE inhibitors, diuretics) and improving contractility. 5-LOX inhibitors have no established role in managing heart failure. * **Hepatic failure:** Management involves treating the underlying cause and complications (e.g., lactulose for encephalopathy). Zileuton is actually contraindicated in active liver disease due to potential hepatotoxicity. * **Arthritis:** While inflammation is a key component, the primary mediators in arthritis are prostaglandins (inhibited by COX-2 inhibitors) and TNF-alpha. 5-LOX inhibitors are not standard therapy for arthritis. **High-Yield Clinical Pearls for NEET-PG:** * **Zileuton** is the specific 5-LOX inhibitor to remember. * **Montelukast and Zafirlukast** are different; they are **Leukotriene Receptor Antagonists (LTRAs)** that block the CysLT1 receptor. * **Aspirin-Exacerbated Respiratory Disease (AERD):** Aspirin shunts arachidonic acid toward the LOX pathway, increasing leukotrienes. LTRAs and 5-LOX inhibitors are particularly effective in this condition. * **Side Effect:** Monitor Liver Function Tests (LFTs) when prescribing Zileuton.

Question 70: Which drugs increase the serum level of theophylline?

A. Ciprofloxacin
B. Cimetidine
C. Allopurinol
D. All of the above (Correct Answer)

Explanation: **Explanation:** Theophylline is a methylxanthine bronchodilator with a **narrow therapeutic index** (10–20 µg/ml). It is primarily metabolized in the liver by the **Cytochrome P450 (CYP1A2 and CYP3A4)** enzyme system. Any drug that inhibits these enzymes will decrease the clearance of theophylline, leading to increased serum levels and potential toxicity (seizures, arrhythmias). * **Ciprofloxacin:** A fluoroquinolone that is a potent inhibitor of CYP1A2. It significantly reduces theophylline clearance, often requiring a dose reduction of 30-50%. * **Cimetidine:** An H2-receptor blocker known as a "pan-enzyme inhibitor." It inhibits multiple CYP isoforms, including those responsible for theophylline metabolism. * **Allopurinol:** Used in gout management, high doses of allopurinol can inhibit the hepatic metabolism of theophylline, leading to elevated plasma concentrations. **Why "All of the above" is correct:** All three drugs act as **enzyme inhibitors**. Since they block the metabolic pathway of theophylline, the drug accumulates in the blood, increasing the risk of toxicity. **High-Yield Clinical Pearls for NEET-PG:** * **Enzyme Inducers (Decrease Theophylline levels):** Phenytoin, Rifampicin, Phenobarbitone, and **Smoking** (induces CYP1A2). * **Enzyme Inhibitors (Increase Theophylline levels):** Erythromycin (Macrolides), Ketoconazole, Ciprofloxacin, Cimetidine, and Oral Contraceptive Pills. * **Toxicity Sign:** The earliest signs of toxicity are usually GI upset (nausea/vomiting), but the most serious are **cardiac arrhythmias** and **intractable seizures**.

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

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Drugs for Pulmonary Hypertension

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Oxygen Therapy

Practice Questions

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