Respiratory System Drugs — MCQs

Respiratory System Drugs Indian Medical PG Practice Questions and MCQs

Question 191: Which of the following anti-asthma drugs is not indicated for oral administration in pregnancy?

A. Salbutamol
B. Prednisolone
C. Theophylline
D. Ipratropium bromide (Correct Answer)

Explanation: ### Explanation The management of asthma in pregnancy focuses on maintaining maternal oxygenation to ensure fetal well-being. The correct answer is **Ipratropium bromide** because it is **not available as an oral formulation**. **1. Why Ipratropium Bromide is the Correct Answer:** Ipratropium bromide is a quaternary ammonium anticholinergic agent. Due to its highly polar nature, it is poorly absorbed from the gastrointestinal tract and does not cross the blood-brain barrier effectively. Consequently, it is administered exclusively via **inhalation** (MDI or nebulization) for local action in the airways. While it is considered safe in pregnancy (Category B), it cannot be "indicated for oral administration" because the dosage form does not exist. **2. Analysis of Incorrect Options:** * **Salbutamol (Option A):** A Short-Acting Beta-2 Agonist (SABA). While inhalation is preferred for quick relief, oral tablets and syrups are available and used in specific clinical scenarios, though less common in modern asthma guidelines. * **Prednisolone (Option B):** A systemic corticosteroid. It is the preferred **oral** steroid for managing acute asthma exacerbations in pregnancy. It is metabolized by placental 11β-HSD2, minimizing fetal exposure. * **Theophylline (Option C):** A methylxanthine available in **oral** sustained-release formulations. Although its use has declined due to a narrow therapeutic index, it remains an option for add-on therapy in pregnant patients. **3. NEET-PG High-Yield Pearls:** * **Drug of Choice (DOC):** Inhaled **Albuterol (Salbutamol)** is the DOC for quick relief in pregnancy. * **Preferred ICS:** **Budesonide** is the most extensively studied and preferred Inhaled Corticosteroid (ICS) for maintenance therapy in pregnancy. * **Safety Rule:** It is safer for a pregnant woman to be treated with asthma medications than to have poorly controlled asthma, which risks fetal hypoxia. * **Leukotriene Antagonists:** Montelukast and Zafirlukast are considered safe for patients who were well-controlled on them prior to pregnancy.

Question 192: A child on $\beta_2$ agonists for treatment of bronchial asthma may exhibit all of the following features EXCEPT:

A. Tremors
B. Hypoglycemia (Correct Answer)
C. Hypokalemia
D. Bronchodilation

Explanation: $\beta_2$ agonists (e.g., Salbutamol, Terbutaline) act by stimulating $\beta_2$ receptors, which are primarily coupled to the $G_s$ protein-adenylyl cyclase pathway. **Explanation of the Correct Answer:** **B. Hypoglycemia:** This is the correct answer because $\beta_2$ agonists actually cause **Hyperglycemia**, not hypoglycemia. Stimulation of $\beta_2$ receptors in the liver and skeletal muscles promotes **glycogenolysis** (breakdown of glycogen to glucose) and **gluconeogenesis**. Additionally, they can stimulate glucagon release, further raising blood glucose levels. **Explanation of Incorrect Options:** * **A. Tremors:** This is the most common side effect. It occurs due to direct stimulation of $\beta_2$ receptors in the **skeletal muscles** (specifically the muscle spindles), leading to rhythmic contractions. * **C. Hypokalemia:** $\beta_2$ stimulation activates the **Na⁺/K⁺-ATPase pump**, causing an inward shift of potassium from the extracellular fluid into the cells (primarily skeletal muscle). This is why salbutamol nebulization is used as an emergency treatment for hyperkalemia. * **D. Bronchodilation:** This is the primary therapeutic effect. Stimulation of $\beta_2$ receptors on bronchial smooth muscle increases intracellular cAMP, leading to muscle relaxation. **NEET-PG High-Yield Pearls:** * **Muscle Tremors** are the dose-limiting side effect of oral $\beta_2$ agonists. * **Tachycardia** can occur via two mechanisms: direct stimulation of cardiac $\beta_2$ receptors and reflex tachycardia due to peripheral vasodilation ($\beta_2$ effect on blood vessels). * **Tolerance (Tachyphylaxis):** Prolonged use leads to down-regulation (internalization) of $\beta_2$ receptors. * **Drug of choice** for acute asthma exacerbations: Inhaled short-acting $\beta_2$ agonists (SABA).

Question 193: A highway truck driver presents with profuse rhinorrhea and sneezing. Which of the following drugs would you prescribe?

A. Pheniramine
B. Promethazine
C. Dimenhydrinate
D. Cetirizine (Correct Answer)

Explanation: The core clinical consideration in this question is the patient’s occupation: a **highway truck driver**. This requires a medication that treats allergic rhinitis without causing sedation or psychomotor impairment, which could lead to road accidents. **1. Why Cetirizine is correct:** Cetirizine is a **Second-Generation Antihistamine (SGA)**. Unlike first-generation drugs, SGAs have poor lipid solubility and high affinity for P-glycoprotein efflux pumps, preventing them from crossing the blood-brain barrier (BBB) in significant amounts. Consequently, they are "non-sedating" and do not interfere with tasks requiring high alertness, making them the drug of choice for drivers, pilots, and heavy machinery operators [1, 2]. **2. Why the other options are incorrect:** * **Pheniramine, Promethazine, and Dimenhydrinate** are all **First-Generation Antihistamines**. These drugs are highly lipophilic and readily cross the BBB, causing significant sedation, drowsiness, and impaired concentration [1, 2]. * **Promethazine** is particularly potent and is often used for its sedative and anti-emetic properties [1, 2]. * **Dimenhydrinate** is primarily used for motion sickness and is highly sedating [2]. * Prescribing any of these to a truck driver would be a safety hazard [1, 2]. **3. NEET-PG High-Yield Pearls:** * **Second-Generation Antihistamines:** Include Cetirizine, Loratadine, Fexofenadine, and Desloratadine. * **Fexofenadine** is considered the least sedating (truly non-sedating) among the SGAs because it does not cross the BBB at all. * **Azelastine** is a topical (nasal spray) SGA often used for rapid relief of allergic rhinitis. * **Side Effects:** First-generation drugs also cause **anti-cholinergic side effects** (dry mouth, blurred vision, urinary retention), which are largely absent in second-generation drugs.

Question 194: Which of the following is a long-acting beta-2 agonist?

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

Explanation: **Explanation:** The correct answer is **Salmeterol**. Beta-2 agonists are categorized based on their duration of action into Short-Acting Beta-Agonists (SABA) and Long-Acting Beta-Agonists (LABA). **1. Why Salmeterol is correct:** Salmeterol is a **Long-Acting Beta-2 Agonist (LABA)**. It possesses a long, lipophilic side chain that anchors the molecule into the cell membrane near the beta-2 receptor, allowing it to repeatedly engage the receptor site. This results in a prolonged duration of action (approximately **12 hours**). Because of its slow onset of action, it is used for maintenance therapy and prophylaxis of asthma and COPD, but never for acute relief. **2. Why the other options are incorrect:** * **Salbutamol (Albuterol):** This is a prototype **Short-Acting Beta-Agonist (SABA)**. It has a rapid onset (5–15 mins) and short duration (4–6 hours), making it the drug of choice for acute bronchospasm (rescue inhaler). * **Terbutaline:** Another SABA similar to Salbutamol. It is often used in emergency settings and can also be administered subcutaneously or used as a tocolytic to delay preterm labor. * **Levalbuterol:** This is the pure R-enantiomer of albuterol. It is also a SABA, marketed with the claim of having fewer side effects (like tachycardia) than racemic albuterol. **NEET-PG High-Yield Pearls:** * **Ultra-LABAs:** Indacaterol, Vilanterol, and Olodaterol have a 24-hour duration and are used once daily (primarily for COPD). * **Black Box Warning:** LABAs should **never** be used as monotherapy in asthma; they must always be combined with an Inhaled Corticosteroid (ICS) to prevent the risk of asthma-related death. * **Formoterol:** A unique LABA that has a **fast onset** of action, allowing it to be used for both maintenance and reliever therapy (SMART therapy).

Question 195: Which of the following antihistamines should be avoided in a truck driver with rhinitis?

A. Diphenhydramine (Correct Answer)
B. Astemizole
C. Desloratadine
D. Fexofenadine

Explanation: **Explanation:** The core concept tested here is the distinction between **First-generation** and **Second-generation** antihistamines (H1 blockers) regarding their ability to cross the blood-brain barrier (BBB). **Why Diphenhydramine is the Correct Answer:** Diphenhydramine is a **First-generation antihistamine**. These drugs are highly lipophilic and readily cross the BBB. Once in the CNS, they block H1 receptors involved in maintaining wakefulness, leading to significant **sedation**, psychomotor impairment, and decreased alertness. For a truck driver, this poses a severe safety risk (comparable to driving under the influence of alcohol). Therefore, it must be avoided. **Why the Other Options are Incorrect:** * **Fexofenadine & Desloratadine:** These are **Second-generation antihistamines**. They are more polar, have low lipid solubility, and are substrates for the P-glycoprotein efflux pump, meaning they do not cross the BBB in significant amounts. They are considered "non-sedating" and are the drugs of choice for individuals in safety-sensitive occupations. * **Astemizole:** This is also a second-generation antihistamine (though largely withdrawn globally due to cardiotoxicity/QT prolongation). Like others in its class, it does not cause significant sedation. **NEET-PG High-Yield Pearls:** * **Least Sedating:** Fexofenadine is often cited as the least sedating antihistamine because it has virtually zero CNS penetration even at high doses. * **First-generation side effects:** Aside from sedation, they cause significant **anticholinergic effects** (dry mouth, blurred vision, urinary retention). * **Metabolism:** Desloratadine is the active metabolite of Loratadine; Fexofenadine is the active metabolite of Terfenadine. * **Clinical Note:** Always advise patients that "non-sedating" antihistamines are preferred for pilots, drivers, and students.

Question 196: Which of the following drugs does NOT cause pulmonary eosinophilia?

A. Nitrofurantoin
B. Penicillin (Correct Answer)
C. Methotrexate
D. Amiodarone

Explanation: **Explanation:** Pulmonary eosinophilia (also known as Drug-Induced Eosinophilic Pneumonia) is characterized by the infiltration of eosinophils into the lung parenchyma, often presenting with cough, fever, and dyspnea. **Why Penicillin is the correct answer:** While Penicillin is notorious for causing **Type I Hypersensitivity (Anaphylaxis)** and **Type II Hypersensitivity (Hemolytic Anemia)**, it is not a classic or common cause of pulmonary eosinophilia. In the context of NEET-PG, drugs like Nitrofurantoin and Methotrexate are the "textbook" examples of drug-induced lung eosinophilia, whereas Penicillin's respiratory manifestations are usually limited to acute bronchospasm during anaphylaxis. **Analysis of Incorrect Options:** * **Nitrofurantoin:** This is the **most common** cause of drug-induced pulmonary eosinophilia. It can cause both acute (hypersensitivity) and chronic (fibrotic) pulmonary reactions. * **Methotrexate:** Known to cause "Methotrexate Lung," which often presents as a hypersensitivity pneumonitis with associated peripheral and tissue eosinophilia. * **Amiodarone:** While primarily known for causing chronic pulmonary fibrosis due to phospholipidosis, it can also present with an acute eosinophilic pneumonia pattern in some patients. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic for Pulmonary Eosinophilia (M-A-N-S):** **M**ethotrexate, **A**miodarone, **N**itrofurantoin, **S**ulfonamides. * **Löffler’s Syndrome:** Often used to describe transient pulmonary infiltrates with blood eosinophilia, commonly caused by parasites (*Ascaris*) or drugs. * **Diagnosis:** Characterized by >25% eosinophils on Bronchoalveolar Lavage (BAL). * **Other notable drugs:** Sulfonamides, Phenytoin, and NSAIDs (especially Naproxen).

Question 197: Which of the following is a second-generation antihistamine?

A. Fexofenadine (Correct Answer)
B. Dimenhydrinate
C. Promethazine
D. Pheneramine

Explanation: **Explanation:** The correct answer is **Fexofenadine**. Antihistamines (H1-receptor antagonists) are classified into two generations based on their ability to cross the blood-brain barrier (BBB) and their sedative potential. **1. Why Fexofenadine is correct:** Fexofenadine is a **second-generation antihistamine**. These drugs are highly polar, have low lipid solubility, and are substrates for the P-glycoprotein efflux pump. Consequently, they do not cross the BBB significantly, resulting in minimal sedation and no anticholinergic side effects. Fexofenadine is actually the active metabolite of Terfenadine and is considered "non-sedating" even at higher doses. **2. Why the other options are incorrect:** * **Dimenhydrinate, Promethazine, and Pheniramine** are all **first-generation antihistamines**. * These drugs are highly lipid-soluble and readily cross the BBB, leading to significant sedation and psychomotor impairment. * They also possess significant **anticholinergic (atropine-like)** properties, which can cause dry mouth, blurred vision, and urinary retention. **High-Yield Clinical Pearls for NEET-PG:** * **Cardiotoxicity:** Terfenadine and Astemizole (2nd gen) were withdrawn because they block delayed rectifier K+ channels, leading to **QT prolongation and Torsades de Pointes**, especially when co-administered with CYP3A4 inhibitors (e.g., Ketoconazole, Erythromycin). **Fexofenadine is safe** and does not cause this. * **Active Metabolites:** Cetirizine is the metabolite of Hydroxyzine; Loratadine is metabolized to Desloratadine. * **Specific Uses:** Promethazine is used for motion sickness and as a pre-anesthetic sedative; Dimenhydrinate is primarily used for vertigo and motion sickness.

Question 198: Which is the commonly used route of administration for Omalizumab in asthma?

A. Subcutaneous (Correct Answer)
B. Inhalational
C. Intradermal
D. Intramuscular

Explanation: **Explanation:** **Omalizumab** is a recombinant DNA-derived humanized monoclonal antibody used in the management of moderate-to-severe persistent allergic asthma. **1. Why Subcutaneous (Option A) is correct:** Omalizumab works by binding specifically to free **IgE** in the plasma, preventing it from binding to the high-affinity IgE receptors (FcεRI) on mast cells and basophils. Due to its proteinaceous nature (monoclonal antibody) and large molecular weight, it cannot be administered orally as it would be degraded by gastric enzymes. It is administered via the **subcutaneous (SC)** route, typically every 2 to 4 weeks, depending on the patient's body weight and serum IgE levels. **2. Why other options are incorrect:** * **Inhalational (Option B):** While most asthma drugs (like Salbutamol or Budesonide) are inhaled for local action, Omalizumab must reach the systemic circulation to neutralize circulating IgE. * **Intradermal (Option C):** This route is used for sensitivity testing (e.g., Mantoux test) but is not suitable for the volume or absorption kinetics required for monoclonal antibodies. * **Intramuscular (Option D):** SC is the preferred parenteral route for Omalizumab to ensure consistent, slow absorption and reduced injection site discomfort compared to IM. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism:** Anti-IgE antibody; it reduces the "early phase" and "late phase" of the allergic response. * **Indication:** Step 5 of GINA guidelines for patients with high IgE levels not controlled by high-dose ICS + LABA. * **Black Box Warning:** Risk of **Anaphylaxis** (though rare, it can occur even after the first dose; patients must be monitored post-injection). * **Other Monoclonal Antibodies in Asthma:** Mepolizumab, Reslizumab, and Benralizumab (all target **IL-5** pathways for eosinophilic asthma).

Question 199: Salbutamol is preferred over adrenaline in an asthmatic patient due to which of the following properties?

A. Beta-1 selectivity
B. Beta-2 selectivity (Correct Answer)
C. Alpha-1 selectivity
D. None of the above

Explanation: **Explanation:** The primary goal in treating bronchial asthma is to achieve bronchodilation while minimizing systemic side effects, particularly cardiovascular stimulation. **1. Why Beta-2 Selectivity is Correct:** Salbutamol is a **selective Beta-2 adrenergic agonist**. Beta-2 receptors are primarily located in the bronchial smooth muscle; their activation leads to increased cAMP, resulting in potent bronchodilation [1]. Unlike Adrenaline, which is a non-selective agonist (acting on $\alpha_1, \alpha_2, \beta_1,$ and $\beta_2$), Salbutamol specifically targets the lungs [2]. This selectivity ensures effective relief of bronchospasm with significantly less cardiac stimulation [1]. **2. Analysis of Incorrect Options:** * **Option A (Beta-1 selectivity):** $\beta_1$ receptors are predominantly found in the heart. Stimulation causes tachycardia and increased myocardial oxygen demand. Drugs like Dobutamine are $\beta_1$ selective; they have no role in bronchodilation. * **Option C (Alpha-1 selectivity):** $\alpha_1$ receptors cause vasoconstriction. While this helps reduce mucosal edema (useful in croup or anaphylaxis), it does not cause bronchodilation. Adrenaline’s $\alpha_1$ action is actually why it is the drug of choice for anaphylaxis, but not for routine asthma [2]. **3. NEET-PG High-Yield Pearls:** * **Drug of Choice:** Salbutamol (SABA) is the drug of choice for **acute asthma attacks** (rescue inhalation) [1]. * **Adrenaline’s Role:** It remains the drug of choice for **Anaphylactic Shock** (given IM 1:1000) because it addresses bronchospasm ($\beta_2$), hypotension ($\alpha_1$), and edema [2]. * **Side Effects of Salbutamol:** Even with $\beta_2$ selectivity, high doses can cause **muscle tremors** (most common), tachycardia (due to $\beta_2$ in the heart and reflex action), and **hypokalemia** [3].

Question 200: Which of the following does not have a role in the acute management of asthma?

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

Explanation: The acute management of asthma focuses on rapid reversal of bronchoconstriction and reduction of airway inflammation. **Why Cromolyn Sodium is the correct answer:** Cromolyn sodium is a **Mast Cell Stabilizer**. It works by preventing the degranulation of mast cells and the subsequent release of inflammatory mediators (like histamine and leukotrienes). However, it has **no direct bronchodilatory action** and cannot reverse existing bronchospasm [3]. Therefore, it is used strictly for **prophylaxis** (preventing exercise-induced or allergen-induced asthma) and has no role in treating an acute attack. **Analysis of Incorrect Options:** * **Salbutamol:** A Short-Acting Beta-2 Agonist (SABA). It is the **drug of choice** for acute asthma due to its rapid onset of action in causing smooth muscle relaxation (bronchodilation) [2]. * **Ipratropium:** An Anticholinergic (SAMA). It blocks M3 receptors, reducing vagal tone and mucus secretion. It is used as an adjunct to SABAs in acute severe asthma (Status Asthmaticus). * **Steroids:** While they have a slow onset (4–6 hours), systemic steroids (e.g., Hydrocortisone or Prednisolone) are vital in acute management to reduce airway edema and prevent late-phase inflammatory responses [1]. **High-Yield NEET-PG Pearls:** * **Cromolyn Sodium:** Not absorbed orally (given via inhalation); main side effect is throat irritation/cough [3]. * **Drug of Choice for Acute Asthma:** Inhaled Salbutamol [2]. * **Drug of Choice for Chronic/Maintenance Asthma:** Inhaled Corticosteroids (ICS) like Fluticasone. * **Magnesium Sulfate:** Used intravenously in life-threatening asthma non-responsive to initial therapy.

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

Want unlimited practice?

Get full access to all questions, explanations, and performance tracking.

Start For Free