Respiratory System Drugs — MCQs

A 28-year-old female with a known history of asthma, currently prescribed inhalational salbutamol, budesonide, and salmeterol, presents with dyspnea. Her peak expiratory flow (PEF) shows mild improvement. Zafirlukast has been added to her treatment regimen. What is the mechanism of action of zafirlukast?

Q90Medium

Which of the following H1 blockers has high anticholinergic activity?

Respiratory System Drugs Indian Medical PG Practice Questions and MCQs

Question 81: Omalizumab is:

A. Interleukin 2 receptor blocker
B. Anti IgE antibody (Correct Answer)
C. Anti IgM antibody
D. Leukotriene receptor blocker

Explanation: **Explanation:** **Omalizumab** is a recombinant DNA-derived humanized monoclonal antibody specifically designed for the management of severe allergic asthma. **1. Why Option B is Correct:** Omalizumab acts as an **Anti-IgE antibody**. It selectively binds to the Fc region of free circulating **IgE** molecules. This binding prevents IgE from attaching to the high-affinity receptors (FcεRI) on the surface of mast cells and basophils. By limiting the degree of IgE receptor binding, it prevents the subsequent degranulation of these cells and the release of inflammatory mediators (like histamine and leukotrienes) upon allergen exposure. **2. Why Incorrect Options are Wrong:** * **Option A (IL-2 Receptor Blocker):** Drugs like **Basiliximab** and Daclizumab are IL-2 receptor blockers, primarily used as immunosuppressants in organ transplantation. * **Option C (Anti-IgM Antibody):** There is no major clinical drug in respiratory pharmacology that acts as an anti-IgM antibody. * **Option D (Leukotriene Receptor Blocker):** This describes **Montelukast** and Zafirlukast, which block the CysLT1 receptor to prevent bronchoconstriction. **3. High-Yield Clinical Pearls for NEET-PG:** * **Indication:** Used in patients (age >6 years) with moderate-to-severe persistent **allergic asthma** who are inadequately controlled with inhaled corticosteroids. * **Route:** Administered **subcutaneously** every 2–4 weeks. * **Key Benefit:** It significantly reduces the frequency of asthma exacerbations and the requirement for oral corticosteroids. * **Side Effect:** The most serious (though rare) side effect is **anaphylaxis**; patients should be monitored after injection. * **Related Drugs:** Do not confuse with **Mepolizumab/Reslizumab** (Anti-IL-5) or **Dupilumab** (Anti-IL-4/IL-13), which are also used in severe eosinophilic asthma.

Question 82: A machinery worker in a factory presents with profuse rhinorrhea and sneezing. Which of the following is the most appropriate medication for symptomatic relief?

A. Diphenhydramine
B. Cetirizine (Correct Answer)
C. Promethazine
D. Hydroxyzine

Explanation: **Explanation:** The patient is presenting with symptoms of allergic rhinitis (rhinorrhea and sneezing). The key clinical consideration in this question is the patient’s occupation: a **machinery worker**. **Why Cetirizine is correct:** Cetirizine is a **second-generation H1 antihistamine**. Unlike first-generation agents, second-generation antihistamines are highly selective for peripheral H1 receptors and have poor lipid solubility, meaning they do not cross the blood-brain barrier significantly. Consequently, they are **non-sedating** and do not impair psychomotor performance. For a machinery worker, avoiding sedation is critical to prevent workplace accidents. **Why the other options are incorrect:** * **Diphenhydramine, Promethazine, and Hydroxyzine** are all **first-generation H1 antihistamines**. These drugs are highly lipophilic and readily cross the blood-brain barrier. They cause significant sedation, drowsiness, and impairment of cognitive/motor functions. * **Promethazine** is particularly known for its strong sedative and anti-emetic properties. * **Hydroxyzine** is often used for its anxiolytic and antipruritic effects but is highly sedating. **High-Yield NEET-PG Pearls:** * **Second-generation antihistamines:** Cetirizine, Loratadine, Fexofenadine, Desloratadine, and Azelastine. * **Fexofenadine** is considered the least sedating of all antihistamines (the "purest" non-sedating agent). * **Cetirizine** is a metabolite of Hydroxyzine; while generally non-sedating, it may cause mild drowsiness in a small percentage of patients compared to Fexofenadine. * **Contraindication:** First-generation antihistamines should be avoided in pilots, drivers, and machinery operators.

Question 83: Which of the following is a lipoxygenase inhibitor?

A. Montelukast
B. Thromboxanes
C. Zileuton (Correct Answer)
D. Sodium cromoglycate

Explanation: **Explanation:** The correct answer is **Zileuton**. This question tests your knowledge of the leukotriene pathway in the management of bronchial asthma. **1. Why Zileuton is correct:** Leukotrienes are potent bronchoconstrictors derived from arachidonic acid via the **5-Lipoxygenase (5-LOX)** enzyme pathway. **Zileuton** is a specific inhibitor of the 5-LOX enzyme. By blocking this enzyme, it prevents the synthesis of all leukotrienes (LTB4, LTC4, LTD4, and LTE4), thereby reducing airway inflammation and bronchospasm. **2. Why other options are incorrect:** * **Montelukast:** This is a **Leukotriene Receptor Antagonist (LTRA)**. It does not inhibit the enzyme; instead, it selectively blocks the **CysLT1 receptor**, preventing the action of cysteinyl leukotrienes (LTC4, LTD4, LTE4). * **Thromboxanes:** These are eicosanoids produced via the **Cyclooxygenase (COX)** pathway, not the lipoxygenase pathway. They primarily mediate platelet aggregation and vasoconstriction. * **Sodium cromoglycate:** This is a **Mast Cell Stabilizer**. It works by preventing the degranulation of mast cells and the subsequent release of inflammatory mediators like histamine; it has no direct effect on the lipoxygenase enzyme. **Clinical Pearls for NEET-PG:** * **Hepatotoxicity:** Zileuton is known to cause a rise in liver enzymes; therefore, periodic **Liver Function Tests (LFTs)** are mandatory. * **Aspirin-Exacerbated Respiratory Disease (AERD):** Leukotriene modifiers (both Zileuton and Montelukast) are particularly effective in patients with the "Samter’s Triad" (Asthma, Aspirin sensitivity, and Nasal polyps). * **Churg-Strauss Syndrome:** Be aware of the rare association between LTRA (Montelukast/Zafirlukast) use and the development of this systemic vasculitis.

Question 84: What is the advantage of salmeterol over salbutamol?

A. Shorter duration of action
B. More potency
C. Longer duration of action (Correct Answer)
D. Lesser cardiac effects

Explanation: **Explanation:** The primary pharmacological difference between Salmeterol and Salbutamol lies in their **pharmacokinetics**, specifically their duration of action. **1. Why "Longer duration of action" 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 $\beta_2$-adrenoceptor. This allows the active head of the drug to repeatedly engage with the receptor site, resulting in a prolonged bronchodilatory effect lasting **12 hours or more**. In contrast, Salbutamol is a **Short-Acting Beta-2 Agonist (SABA)** with a duration of only 4–6 hours. **2. Why other options are incorrect:** * **Shorter duration of action:** This describes Salbutamol (SABA), which is used for "rescue" relief of acute symptoms. * **More potency:** While their binding affinities differ, "potency" is not the clinically defining advantage. The therapeutic choice is based on the *timing* of the effect. * **Lesser cardiac effects:** Both drugs are $\beta_2$-selective but can cause tachycardia and tremors at high doses due to some $\beta_1$ cross-reactivity or reflex mechanisms. Salmeterol does not inherently possess a significantly safer cardiac profile than Salbutamol. **Clinical Pearls for NEET-PG:** * **Onset of Action:** Salbutamol acts within 5 minutes (ideal for acute attacks). Salmeterol has a **slow onset** (15–20 mins) and should **never** be used for acute relief. * **Black Box Warning:** LABAs (Salmeterol/Formoterol) should generally not be used as monotherapy in asthma; they must be combined with an **Inhaled Corticosteroid (ICS)** to reduce the risk of asthma-related mortality. * **Formoterol Exception:** Unlike Salmeterol, Formoterol is a LABA that has a **fast onset** of action.

Question 85: What is the drug of choice for the treatment of acute asthmatic attacks?

A. Leukotriene antagonists
B. Lipoxygenase inhibitors
C. Beta 2 agonists (Correct Answer)
D. Anticholinergics

Explanation: **Explanation:**Why Beta-2 Agonists are the Correct Choice:Short-acting Beta-2 Agonists (SABA), such as **Salbutamol (Albuterol)** and Terbutaline, are the drugs of choice for acute asthmatic attacks [1, 3]. Their mechanism involves stimulating $\beta_2$ receptors on bronchial smooth muscle, leading to increased intracellular cAMP. This results in rapid and potent **bronchodilation**, providing immediate relief from symptoms like wheezing and dyspnea [2]. Because they have a rapid onset of action (within 5 minutes), they are termed "rescue medications."Analysis of Incorrect Options:* **Leukotriene Antagonists (e.g., Montelukast):** These are used for **prophylaxis** and chronic management of asthma, especially aspirin-induced or exercise-induced asthma. They are not effective in acute attacks because they do not provide immediate bronchodilation.* **Lipoxygenase Inhibitors (e.g., Zileuton):** Similar to leukotriene antagonists, these are controller medications used for long-term maintenance, not for emergency relief.* **Anticholinergics (e.g., Ipratropium bromide):** While they cause bronchodilation by blocking M3 receptors, they are slower-acting and less potent than $\beta_2$ agonists. They are typically used as **add-on therapy** in acute severe asthma or as the drug of choice in COPD.High-Yield Clinical Pearls for NEET-PG:* **Route of Choice:** Inhalation is preferred over oral/parenteral routes for acute attacks to ensure rapid action and minimal systemic side effects (like tremors and tachycardia).* **Drug of Choice for Exercise-Induced Asthma:** SABA (taken 15 minutes before exercise).* **Status Asthmaticus:** If SABA fails, the next steps include systemic corticosteroids and nebulized Ipratropium.* **Side Effects:** Muscle tremors (most common), palpitations, and hypokalemia (due to shift of $K^+$ into cells).

Question 86: What is the most unpleasant side effect of salbutamol?

A. Tremors (Correct Answer)
B. Hypertension
C. Rhinorrhoea
D. Headache

Explanation: Salbutamol is a Short-Acting Beta-2 Agonist (SABA) primarily used as a bronchodilator in asthma and COPD. **Why Tremors are the correct answer:** The most common and characteristic side effect of Salbutamol is **skeletal muscle tremors**, specifically involving the hands. This occurs due to the direct stimulation of **Beta-2 receptors located on the voluntary skeletal muscles**. This stimulation causes an increase in the speed of muscle contraction and a decrease in the refractory period, leading to fine tremors. While not life-threatening, patients find this side effect highly "unpleasant" and distressing, often affecting their manual dexterity. **Analysis of Incorrect Options:** * **B. Hypertension:** Salbutamol primarily acts on Beta-2 receptors (vasodilation), which typically causes a slight decrease or no change in blood pressure. While high doses can cause reflex tachycardia via Beta-1 stimulation, hypertension is not a standard side effect [1, 2]. * **C. Rhinorrhoea:** This is not associated with Beta-agonists. In fact, alpha-agonists are used to treat rhinorrhoea (nasal congestion). * **D. Headache:** While headaches can occur due to vasodilation, they are less frequent and less characteristic than tremors. **NEET-PG High-Yield Pearls:** 1. **Tolerance:** Continuous use of Salbutamol leads to **downregulation (tachyphylaxis)** of Beta-2 receptors. 2. **Metabolic Effect:** Salbutamol can cause **hypokalemia** (by driving potassium into cells), which is why it is used therapeutically in hyperkalemia. 3. **Drug of Choice:** Salbutamol remains the drug of choice for **acute episodes** (rescue inhaler) of bronchospasm. 4. **Tachycardia:** Occurs due to both direct Beta-1 stimulation (at high doses) and reflex action due to Beta-2 mediated peripheral vasodilation [1, 2].

Question 87: What are the complications of inhalational steroid use?

A. Cushing's syndrome
B. Oral candidiasis (Correct Answer)
C. Decreased ACTH
D. Systemic complications

Explanation: **Explanation:** Inhalational corticosteroids (ICS), such as Budesonide and Fluticasone, are the mainstay for long-term management of bronchial asthma. The primary advantage of the inhalational route is that it delivers the drug directly to the target site (airway), minimizing systemic absorption and associated side effects. **Why Oral Candidiasis is the Correct Answer:** When using a Metered-Dose Inhaler (MDI), a significant portion of the drug (approx. 80-90%) deposits in the oropharynx. Steroids cause local immunosuppression in the oral mucosa, which facilitates the overgrowth of opportunistic fungi, most commonly *Candida albicans*. This results in **Oral Candidiasis (Thrush)**. Another common local side effect is **Dysphonia** (hoarseness of voice) due to myopathy of the laryngeal muscles. **Analysis of Incorrect Options:** * **A & C (Cushing’s Syndrome & Decreased ACTH):** These are features of systemic corticosteroid toxicity. While high doses of potent ICS can theoretically cause some adrenal suppression, they rarely cause full-blown Cushingoid features or significant ACTH suppression at standard therapeutic doses. * **D (Systemic Complications):** The inhalational route is specifically designed to avoid systemic complications like osteoporosis, hyperglycemia, and growth retardation, which are common with oral or parenteral steroids. **High-Yield Clinical Pearls for NEET-PG:** * **Prevention:** Patients should be advised to **rinse their mouth with water and spit** after every use of an ICS to remove oropharyngeal deposits. * **Spacers:** Using a spacer device with an MDI reduces oropharyngeal deposition and increases lung delivery, further decreasing the risk of candidiasis. * **Ciclesonide:** This is a **prodrug** activated by esterases in the lungs; it has minimal activity in the oropharynx, significantly reducing the risk of local side effects.

Question 88: Salbutamol is used in which of the following conditions?

A. Cardiac asthma
B. Bronchial asthma (Correct Answer)
C. Pulmonary oedema
D. Cor pulmonale

Explanation: ### Explanation **Correct Option: B. Bronchial Asthma** Salbutamol is a **short-acting beta-2 ($\beta_2$) agonist (SABA)**. Its primary mechanism involves stimulating $\beta_2$ receptors located on the bronchial smooth muscle. This activation increases intracellular cyclic AMP (cAMP), leading to potent **bronchodilation**. It is the drug of choice for the relief of acute bronchospasm in bronchial asthma because of its rapid onset of action (5–15 minutes). **Why other options are incorrect:** * **A. Cardiac Asthma:** This is not true asthma; it is wheezing caused by left-sided heart failure leading to pulmonary congestion. The primary treatment involves diuretics (Furosemide) and morphine, not bronchodilators. * **C. Pulmonary Oedema:** This is an accumulation of fluid in the lungs, usually due to heart failure. Treatment focuses on reducing preload (nitrates, diuretics) and improving cardiac output. Salbutamol has no role here and may even worsen tachycardia. * **D. Cor Pulmonale:** This refers to right-sided heart failure resulting from chronic lung disease (like COPD). While bronchodilators may treat the underlying COPD, Salbutamol is not a treatment for the resulting heart failure itself. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism:** Increases cAMP $\rightarrow$ Bronchodilation. * **Side Effects:** Muscle tremors (most common), tachycardia (due to $\beta_1$ cross-reactivity), and **hypokalemia** (used therapeutically to treat hyperkalemia). * **Drug of Choice:** Salbutamol/Albuterol is the "rescue inhaler" for acute asthma attacks. * **Contraindication:** Use with caution in patients with hyperthyroidism or severe cardiac disease due to risk of arrhythmias.

Question 89: A 28-year-old female with a known history of asthma, currently prescribed inhalational salbutamol, budesonide, and salmeterol, presents with dyspnea. Her peak expiratory flow (PEF) shows mild improvement. Zafirlukast has been added to her treatment regimen. What is the mechanism of action of zafirlukast?

A. Inhibition of the actions of LTB4
B. Inhibition of the actions of LTC4, LTD4 (Correct Answer)
C. Inhibition of the formation of LTC4, LTD4
D. Inhibition of the release of leukotrienes from mast cells

Explanation: ### Explanation **1. Mechanism of Action (Correct Answer: B)** Zafirlukast and Montelukast are **selective CysLT₁ receptor antagonists**. In asthma, cysteinyl leukotrienes (LTC4, LTD4, and LTE4) are potent bronchoconstrictors that also increase mucus secretion and airway edema. By competitively blocking the CysLT₁ receptor, zafirlukast inhibits the **actions** of these leukotrienes, leading to bronchodilation and reduced airway inflammation. **2. Analysis of Incorrect Options** * **Option A:** LTB4 is primarily a chemoattractant for neutrophils. While it plays a role in inflammation, CysLT₁ antagonists do not target LTB4 receptors. * **Option C:** This describes the mechanism of **Zileuton**, which is a 5-Lipoxygenase (5-LOX) inhibitor. Zileuton prevents the *synthesis* (formation) of leukotrienes, whereas zafirlukast blocks their *receptors*. * **Option D:** This describes the mechanism of **Mast Cell Stabilizers** (e.g., Sodium Cromoglicate), which prevent the degranulation and release of various mediators, including leukotrienes. **3. NEET-PG High-Yield Clinical Pearls** * **Indications:** Used for prophylactic treatment of chronic asthma and aspirin-induced asthma (AIA). They are **not** used for acute attacks. * **Metabolism:** Zafirlukast is an inhibitor of CYP2C9 and CYP3A4; it can increase the serum levels of **Warfarin**, leading to increased prothrombin time. * **Side Effects:** Generally well-tolerated, but rarely associated with **Churg-Strauss syndrome** (eosinophilic granulomatosis with polyangiitis) when systemic steroids are tapered. * **Administration:** Montelukast is taken once daily (usually at night), while Zafirlukast is taken twice daily.

Question 90: Which of the following H1 blockers has high anticholinergic activity?

A. Cetirizine
B. Chlorpheniramine (Correct Answer)
C. Fexofenadine
D. Astemizole

Explanation: <h3>Explanation</h3>1. Why Chlorpheniramine is Correct: Chlorpheniramine is a **first-generation H1 antihistamine** [1, 3]. First-generation antihistamines are highly lipophilic, allowing them to cross the blood-brain barrier (causing sedation) [2, 3] and lack selectivity for the H1 receptor. They possess significant affinity for **muscarinic receptors**, leading to potent **anticholinergic effects** (e.g., dry mouth, blurred vision, urinary retention, and constipation) [1, 3]. In clinical practice, its anticholinergic property is often utilized to dry up nasal secretions in common cold formulations.2. Why the Other Options are Incorrect: <ul><li> **Cetirizine (Option A):** This is a **second-generation** antihistamine [2]. While it is a metabolite of hydroxyzine and can cause mild sedation in some patients, it has negligible anticholinergic activity compared to first-generation drugs [2].</li><li> **Fexofenadine (Option C):** A highly selective **second-generation** H1 blocker [2]. It does not cross the blood-brain barrier and is virtually devoid of anticholinergic side effects, making it one of the "non-sedating" antihistamines [2].</li><li> **Astemizole (Option D):** An older second-generation antihistamine. Like fexofenadine, it lacks significant anticholinergic activity. (Note: It has been largely withdrawn globally due to the risk of Torsades de Pointes).</li></ul>3. High-Yield Clinical Pearls for NEET-PG: <ul><li> **Classification:** First-generation H1 blockers are divided by chemical class. Chlorpheniramine belongs to the **Alkylamines** group (low sedation, high potency) [3].</li><li> **Other High Anticholinergic H1 Blockers:** Diphenhydramine, Promethazine, and Dimenhydrinate [1].</li><li> **Clinical Contraindication:** Due to their anticholinergic profile, first-generation antihistamines should be used with caution in patients with **Glaucoma** (can increase intraocular pressure) and **Benign Prostatic Hyperplasia (BPH)** (can cause acute urinary retention).</li><li> **Drug of Choice:** For motion sickness, H1 blockers with high anticholinergic activity (like Promethazine or Diphenhydramine) are preferred [1].</li></ul>

Practice by Chapter

Bronchodilators

Practice Questions

Corticosteroids in Respiratory Disorders

Practice Questions

Anti-inflammatory Respiratory Agents

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Mast Cell Stabilizers

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Leukotriene Modifiers

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Antitussives and Expectorants

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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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