Respiratory System Drugs — MCQs

Respiratory System Drugs Indian Medical PG Practice Questions and MCQs

Question 101: Beta agonists used in bronchial asthma exert their action by which mechanism?

A. Selective beta-1 agonism
B. Selective beta-2 agonism (Correct Answer)
C. Selective beta-1 antagonism
D. Selective beta-2 antagonism

Explanation: **Explanation:** **Mechanism of Action (Why B is correct):** Beta-agonists (e.g., Salbutamol, Salmeterol) act by binding to **$\beta_2$-adrenergic receptors** located on the smooth muscle cells of the bronchi. This binding activates the enzyme **adenylyl cyclase**, which increases intracellular levels of **cyclic AMP (cAMP)**. Elevated cAMP leads to a decrease in intracellular calcium and activation of protein kinase A, resulting in potent **bronchodilation**. This is the mainstay treatment for relieving bronchospasm in asthma. **Analysis of Incorrect Options:** * **Option A (Selective $\beta_1$ agonism):** $\beta_1$ receptors are primarily located in the **heart**. Agonism here increases heart rate (chronotropy) and contractility (inotropy). It does not cause significant bronchodilation and would lead to unwanted cardiovascular side effects. * **Option C & D (Antagonism):** Antagonists (Beta-blockers) inhibit the receptor. $\beta_2$ antagonism (Option D) is actually **contraindicated** in asthma because it causes bronchoconstriction, which can precipitate a life-threatening asthma attack. **NEET-PG High-Yield Pearls:** * **SABA (Short-Acting Beta Agonists):** Salbutamol, Terbutaline. Drug of choice for **acute** asthma attacks (Rescue inhalers). * **LABA (Long-Acting Beta Agonists):** Salmeterol, Formoterol. Used for **maintenance** therapy; should always be combined with Inhaled Corticosteroids (ICS). * **Side Effects:** Muscle tremors (most common, due to $\beta_2$ receptors in skeletal muscles), tachycardia (due to minor $\beta_1$ cross-reactivity), and **hypokalemia** (due to stimulation of Na+/K+ ATPase pump).

Question 102: What is the most common side effect of inhaled beclomethasone?

A. Adrenal suppression
B. Oropharyngeal candidiasis (Correct Answer)
C. Bronchoconstriction
D. Hepatitis

Explanation: **Explanation:** **Inhaled Beclomethasone** is a potent inhaled corticosteroid (ICS) used for the long-term management of bronchial asthma [1]. **Why Oropharyngeal Candidiasis is correct:** The primary mechanism of ICS involves local immunosuppression in the oral cavity and pharynx. When the drug particles deposit on the oral mucosa, they inhibit local cell-mediated immunity, allowing the overgrowth of opportunistic fungi, most commonly *Candida albicans*. This presents clinically as "oral thrush" (white, scrapable patches). **Analysis of Incorrect Options:** * **A. Adrenal suppression:** While a known side effect of systemic steroids, it is rare with inhaled forms unless used in very high doses for prolonged periods, as ICS have low systemic bioavailability [1]. * **C. Bronchoconstriction:** ICS are used to reduce airway inflammation and prevent bronchoconstriction [2]. While rare "paradoxical bronchospasm" can occur with any inhaler due to additives, it is not the most common side effect. * **D. Hepatitis:** Corticosteroids are not typically hepatotoxic; in fact, systemic steroids are sometimes used to treat autoimmune hepatitis. **NEET-PG High-Yield Pearls:** 1. **Prevention:** To minimize the risk of candidiasis and **dysphonia** (hoarseness of voice), patients should be advised to **rinse their mouth with water and spit** after every use [1]. 2. **Spacer Devices:** Using a large-volume spacer reduces oropharyngeal deposition and increases lung delivery, further decreasing local side effects [1]. 3. **Ciclesonide:** This is a "prodrug" activated by esterases in the lungs; it has the lowest risk of oral candidiasis because it is not active while passing through the oropharynx [1].

Question 103: Which of the following is a long-acting bronchodilator?

A. Salbutamol
B. Terbutaline
C. Adrenaline
D. Formoterol (Correct Answer)

Explanation: ### Explanation **Correct Answer: D. Formoterol** **Mechanism and Classification:** Formoterol is a **Long-Acting Beta-2 Agonist (LABA)**. It works by stimulating $\beta_2$ receptors in the bronchial smooth muscle, leading to increased intracellular cAMP and subsequent bronchodilation. Unlike short-acting agents, LABAs have a long lipophilic side chain that binds to the "exosite" near the $\beta_2$ receptor, allowing for a prolonged duration of action (approximately 12 hours). Formoterol is unique because it has a **fast onset of action** (similar to Salbutamol) despite its long duration, making it suitable for both maintenance and "SMART" (Single Maintenance and Reliever Therapy) in asthma. **Analysis of Incorrect Options:** * **A. Salbutamol (Albuterol):** A Short-Acting Beta-2 Agonist (SABA). It is the drug of choice for acute asthma attacks due to its rapid onset, but its duration is only 4–6 hours. * **B. Terbutaline:** Another SABA similar to Salbutamol. It is used for quick relief of bronchospasm and is also used off-label as a tocolytic to delay preterm labor. * **C. Adrenaline (Epinephrine):** A non-selective $\alpha$ and $\beta$ agonist. While it causes potent bronchodilation, it is ultra-short-acting and carries significant cardiac side effects. It is the drug of choice for **Anaphylaxis**, not routine asthma management. **High-Yield NEET-PG Pearls:** * **LABAs vs. SABAs:** Salmeterol and Formoterol are LABAs (12 hrs); Indacaterol, Vilanterol, and Olodaterol are **Ultra-LABAs** (24 hrs). * **Black Box Warning:** LABAs should **never** be used as monotherapy in asthma (risk of asthma-related death); they must always be combined with an Inhaled Corticosteroid (ICS). * **Salmeterol vs. Formoterol:** Salmeterol has a slow onset; Formoterol has a rapid onset. * **Side Effects:** Muscle tremors (most common), tachycardia, and hypokalemia.

Question 104: Which new drug has been approved for the treatment of drug-resistant tuberculosis?

A. Bedaquiline (Correct Answer)
B. Ibalizumab
C. Bectegravir
D. Apalutamide

Explanation: **Explanation:** **Bedaquiline** is the correct answer. It is a diarylquinoline and represents the first new class of anti-tuberculosis drugs approved by the FDA in over 40 years. Its unique mechanism of action involves the **inhibition of mycobacterial ATP synthase**, an enzyme essential for energy production in *Mycobacterium tuberculosis*. It is specifically indicated for Multi-Drug Resistant TB (MDR-TB) as part of combination therapy when other regimens are ineffective. **Analysis of Incorrect Options:** * **Ibalizumab:** A humanized monoclonal antibody used as an entry inhibitor for the treatment of multidrug-resistant **HIV-1** infection. It binds to domain 2 of the CD4 receptor. * **Bictegravir:** A potent **Integrase Strand Transfer Inhibitor (INSTI)** used in the treatment of HIV/AIDS, typically found in combination tablets (e.g., Biktarvy). * **Apalutamide:** A non-steroidal **anti-androgen** medication used primarily in the treatment of metastatic and non-metastatic castration-resistant prostate cancer. **High-Yield Clinical Pearls for NEET-PG:** * **Black Box Warning:** Bedaquiline can cause **QTc prolongation**; therefore, ECG monitoring is mandatory, especially when co-administered with other QT-prolonging drugs like Clofazimine or Moxifloxacin. * **Metabolism:** It is metabolized by the **CYP3A4** enzyme; hence, potent inducers like Rifampin should be avoided. * **WHO Guidelines:** Bedaquiline is now classified as a **Group A** drug (highly effective) in the treatment of MDR-TB, replacing older injectables like Kanamycin/Capreomycin. * **BPaL Regimen:** A modern, highly effective short-course regimen for XDR-TB consisting of **B**edaquiline, **P**retomanid, and **L**inezolid.

Question 105: All of the following are antitussives EXCEPT:

A. Codeine
B. Dextromethorphan
C. Ambroxol (Correct Answer)
D. Noscapine

Explanation: **Explanation:** The primary goal of an **antitussive** is to suppress the cough reflex. These drugs are indicated for dry, non-productive coughs. In contrast, **Ambroxol** is a **mucolytic agent**. It works by thinning and loosening bronchial secretions (mucus) by breaking down acid mucopolysaccharide fibers, making it easier for the patient to expectorate. Therefore, it is used for productive coughs, not as a cough suppressant. **Analysis of Options:** * **Codeine (Option A):** An opioid derivative that acts centrally on the cough center in the medulla. It is considered the "gold standard" antitussive but carries risks of sedation and constipation. * **Dextromethorphan (Option B):** A synthetic NMDA receptor antagonist. It is a centrally acting antitussive that is as effective as codeine but lacks analgesic or addictive properties, making it a common ingredient in OTC cough syrups. * **Noscapine (Option C):** An opium alkaloid (isoquinoline derivative) that suppresses cough without causing narcosis or dependence. It is particularly useful in spasmodic coughs. **NEET-PG High-Yield Pearls:** 1. **Classification:** Antitussives are classified into **Centrally acting** (Opioids: Codeine, Pholcodine; Non-opioids: Dextromethorphan, Noscapine) and **Peripherally acting** (Prenoxdiazine, Benzonatate). 2. **Benzonatate:** Acts by anesthetizing the stretch receptors in the lungs (Hering-Breuer reflex). 3. **Ambroxol vs. Bromhexine:** Ambroxol is a metabolite of Bromhexine; both act as mucolytics and also stimulate surfactant production. 4. **Contraindication:** Antitussives should be avoided in productive coughs as suppressing the cough can lead to sputum retention and secondary infections.

Question 106: What drug is locally used for tracheal stenosis?

A. Mitomycin C (Correct Answer)
B. Doxorubicin
C. Bleomycin
D. Clindamycin

Explanation: **Explanation:** **Mitomycin C** is the correct answer because of its potent **antifibrotic properties**. It is an alkylating agent derived from *Streptomyces caespitosus* that inhibits DNA synthesis. When applied topically (locally) to the site of a tracheal injury or after surgical dilation, it inhibits the proliferation of **fibroblasts** and reduces the production of collagen. This prevents the formation of excessive scar tissue (granulation tissue), which is the primary cause of recurrent tracheal stenosis. **Analysis of Incorrect Options:** * **B. Doxorubicin:** An anthracycline antibiotic used in systemic chemotherapy (e.g., breast cancer, lymphomas). It is highly cardiotoxic and is not used locally for airway remodeling. * **C. Bleomycin:** While it is an antitumor antibiotic used for sclerotherapy (e.g., in cystic hygromas) or intralesional treatment of warts, its systemic use is actually associated with **pulmonary fibrosis**, making it unsuitable for preventing stenosis. * **D. Clindamycin:** A lincosamide antibiotic used to treat anaerobic infections and MRSA. It has no effect on fibroblast proliferation or scar modulation. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism:** Mitomycin C acts as an alkylating agent that cross-links DNA (specifically at the 5' amino group of guanine). * **Other Local Uses:** In Ophthalmology, it is used topically during **Glaucoma filtration surgery (Trabeculectomy)** and Pterygium surgery to prevent scarring. * **Application:** In tracheal stenosis, it is typically applied via a soaked cotton pledget (concentration 0.4–0.5 mg/mL) for 2–5 minutes. * **Key Side Effect (Systemic):** Delayed bone marrow suppression (thrombocytopenia and leukopenia).

Question 107: Systemic adverse effects of long-term inhaled corticosteroids are typically evident at daily doses exceeding which of the following thresholds?

A. 200 mcg/day
B. 400 mcg/day
C. 600 mcg/day (Correct Answer)
D. 800 mcg/day

Explanation: ### Explanation **Correct Option: C (600 mcg/day)** Inhaled Corticosteroids (ICS) are the cornerstone of chronic asthma management. While they are designed for local action in the lungs, a portion of the dose is inevitably absorbed into the systemic circulation via the lungs or the gastrointestinal tract (if swallowed). Clinical studies and pharmacological guidelines indicate that in adults, the threshold for **systemic adverse effects**—such as hypothalamic-pituitary-adrenal (HPA) axis suppression, decreased bone mineral density, and skin thinning—typically becomes clinically evident when the daily dose exceeds **600 mcg of Beclomethasone dipropionate (BDP) equivalent** [1]. Below this dose, the systemic bioavailability is generally low enough that the liver's first-pass metabolism and the high topical-to-systemic potency ratio prevent significant side effects. **Analysis of Incorrect Options:** * **A (200 mcg/day) & B (400 mcg/day):** These are considered "Low Doses." At these levels, ICS are highly safe with negligible systemic absorption. Side effects at these doses are usually limited to local issues like oropharyngeal candidiasis or dysphonia. * **D (800 mcg/day):** While systemic effects are certainly present at this dose, it is considered a "High Dose." The question asks for the threshold where these effects *begin* to be evident, which occurs earlier at the 600 mcg mark (the transition to "Medium-High" dosing). **High-Yield Clinical Pearls for NEET-PG:** * **Local Side Effects:** Prevented by using a **spacer device** and **gargling with water** after inhalation [1]. * **Ciclesonide:** A "prodrug" activated by bronchial esterases; it has the lowest systemic side effect profile because it remains inactive until it reaches the lungs [1]. * **Fluticasone:** Has very low oral bioavailability (<1%) due to high first-pass metabolism, making the swallowed portion less likely to cause systemic effects compared to older ICS [1]. * **Monitoring:** In children, long-term high-dose ICS requires monitoring of growth velocity.

Question 108: 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** (status asthmaticus or acute exacerbation) requires drugs with a rapid onset of action to reverse bronchospasm and reduce airway inflammation immediately. **Why Montelukast is the correct answer:** Montelukast is a **Leukotriene Receptor Antagonist (LTRA)**. It works by blocking the CysLT1 receptor. While effective for the long-term prophylaxis of asthma and management of aspirin-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 other options:** * **Salbutamol (Option A):** A Short-Acting Beta-2 Agonist (SABA). It is the **drug of choice** for acute asthma due to its rapid onset (2–5 minutes) in causing bronchodilation. * **Ipratropium (Option B):** A Short-Acting Muscarinic Antagonist (SAMA). It is used as an adjunct to SABAs in acute severe asthma to provide synergistic bronchodilation by blocking vagal-mediated bronchoconstriction. * **Hydrocortisone (Option D):** A systemic corticosteroid. It is administered intravenously in acute severe asthma to reduce airway inflammation and upregulate beta-receptors, preventing late-phase relapse. **High-Yield NEET-PG Pearls:** 1. **Drug of Choice for Acute Asthma:** Inhaled Salbutamol (SABA). 2. **Drug of Choice for Prophylaxis (Chronic Asthma):** Inhaled Corticosteroids (e.g., Fluticasone, Budesonide). 3. **Aspirin-Induced Asthma:** LTRAs like Montelukast are particularly effective here. 4. **Magnesium Sulfate:** Used intravenously in life-threatening asthma non-responsive to initial therapy.

Question 109: Which drug is NOT used in the management of bronchial asthma?

A. Phosphodiesterase inhibitor
B. Steroids
C. Beta agonist
D. Cholinergic drugs (Correct Answer)

Explanation: The management of bronchial asthma focuses on reversing bronchoconstriction and reducing airway inflammation. Why Cholinergic drugs are the correct answer:Cholinergic drugs (parasympathomimetics) act on M3 receptors in the bronchial smooth muscle to cause **bronchoconstriction** and increased mucus secretion. This would exacerbate asthma symptoms rather than treat them. In contrast, **Anticholinergic drugs** (e.g., Ipratropium, Tiotropium) are used in asthma management because they block these receptors, leading to bronchodilation [2, 3].Analysis of Incorrect Options: * **Phosphodiesterase (PDE) inhibitors:** Drugs like Theophylline inhibit PDE, increasing intracellular cAMP levels, which leads to bronchodilation. They also possess mild anti-inflammatory properties [3]. * **Steroids:** These are the mainstay for controlling airway inflammation. Inhaled corticosteroids (e.g., Fluticasone, Budesonide) reduce bronchial hyperreactivity and prevent remodeling [1, 2]. * **Beta agonists:** These are the most potent bronchodilators. They stimulate {2} receptors, increasing cAMP and causing rapid relaxation of bronchial smooth muscle [1, 3]. They are classified into SABA (Salbutamol) for acute relief and LABA (Salmeterol) for maintenance [1, 2].High-Yield Clinical Pearls for NEET-PG: * **Drug of choice for acute asthma:** SABA (Inhaled Salbutamol) [1]. * **Drug of choice for maintenance/prophylaxis:** Inhaled Corticosteroids (ICS) [1, 2]. * **Mechanism of Ipratropium:** It is a non-selective muscarinic antagonist; it is particularly useful in psychogenic asthma or when -blockers induce bronchospasm [2]. * **Roflumilast:** A selective PDE-4 inhibitor used primarily in COPD, not typically for acute asthma.

Question 110: Theophylline causes diuresis because of?

A. Beta 2 agonism
B. PDE 3 inhibition
C. PDE 4 inhibition
D. Adenosine A1 receptor antagonism (Correct Answer)

Explanation: **Explanation:** Theophylline is a methylxanthine derivative used in the management of asthma and COPD. Its diuretic effect is primarily mediated through the **antagonism of Adenosine A1 receptors** in the kidneys. 1. **Mechanism of Diuresis (Option D):** Adenosine, acting on A1 receptors in the renal tubules and afferent arterioles, normally promotes sodium reabsorption and causes vasoconstriction to reduce glomerular filtration rate (GFR). By antagonizing these A1 receptors, theophylline induces **vasodilation of the afferent arteriole** (increasing GFR) and **inhibits sodium reabsorption** in the proximal tubule, leading to increased water and salt excretion (diuresis). 2. **Analysis of Incorrect Options:** * **Option A (Beta 2 agonism):** This is the mechanism of drugs like Salbutamol. While Beta-2 agonists cause bronchodilation, they do not cause diuresis; in fact, they may cause reflex tachycardia and hypokalemia. * **Option B & C (PDE 3 & 4 inhibition):** Theophylline does inhibit Phosphodiesterase (PDE) enzymes non-selectively. PDE-3 inhibition contributes to cardiac stimulation, while **PDE-4 inhibition** is the primary mechanism for **bronchodilation** and anti-inflammatory effects. However, these are not the drivers of its diuretic action. **High-Yield Clinical Pearls for NEET-PG:** * **Therapeutic Window:** Theophylline has a narrow therapeutic index (10–20 µg/ml). Toxicity occurs >20 µg/ml. * **Metabolism:** It is metabolized by **CYP1A2**. Enzyme inhibitors (e.g., Cimetidine, Erythromycin, Ciprofloxacin) can lead to toxicity. * **Adverse Effects:** At high doses, it causes seizures (due to A1 antagonism in the CNS) and cardiac arrhythmias (due to PDE inhibition and increased cAMP). * **DOC for Apnea of Prematurity:** Caffeine (another methylxanthine) is preferred over theophylline due to a wider safety margin.

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

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