Respiratory System Drugs — MCQs

Respiratory System Drugs Indian Medical PG Practice Questions and MCQs

Question 71: What is the mechanism of action of corticosteroids in asthma?

A. Decreases mucosal edema by suppressing inflammatory response (Correct Answer)
B. Mast cell stabilization
C. Cause bronchodilation
D. Leukotriene receptor antagonism

Explanation: **Explanation:** **Mechanism of the Correct Answer (A):** Corticosteroids (e.g., Fluticasone, Prednisolone) are the most effective anti-inflammatory agents for asthma. They act by binding to intracellular glucocorticoid receptors, leading to the downregulation of pro-inflammatory genes (IL-4, IL-5, TNF-α) and the upregulation of anti-inflammatory proteins. This results in decreased recruitment of eosinophils and T-lymphocytes, reduced capillary permeability, and inhibition of cytokine release. Consequently, they **decrease mucosal edema** and airway hyper-responsiveness, addressing the underlying pathology of asthma rather than just the symptoms. **Analysis of Incorrect Options:** * **B. Mast cell stabilization:** This is the mechanism of **Sodium Cromoglycate** and Nedocromil. While steroids reduce the number of mast cells over long-term use, they do not stabilize the cell membrane to prevent immediate degranulation. * **C. Cause bronchodilation:** Corticosteroids have **no direct bronchodilatory effect**. They are "preventers," not "relievers." However, they do potentiate the effects of β2-agonists by increasing the expression of β2-receptors on airway smooth muscle. * **D. Leukotriene receptor antagonism:** This is the mechanism of **Montelukast** and Zafirlukast. Steroids inhibit the synthesis of leukotrienes (via Phospholipase A2 inhibition) but do not block the receptors. **High-Yield NEET-PG Pearls:** * **Drug of Choice:** Inhaled Corticosteroids (ICS) are the first-line maintenance therapy for all grades of persistent asthma. * **Synergy:** Steroids reverse β2-receptor desensitization, making them crucial in managing tachyphylaxis. * **Side Effects:** The most common local side effects of ICS are **Oropharyngeal Candidiasis** (thrush) and **Dysphonia** (hoarseness). These can be minimized by using a spacer and rinsing the mouth after inhalation.

Question 72: The release of histamine and leukotrienes from mast cells is prevented by which of the following drugs?

A. Zileuton
B. Nedocromil sodium (Correct Answer)
C. Zafirlukast
D. Fexofenadine

Explanation: **Explanation:** The correct answer is **Nedocromil sodium**. This drug belongs to the class of **Mast Cell Stabilizers**. **1. Why Nedocromil sodium is correct:** Mast cell stabilizers (including Cromolyn sodium and Nedocromil) work by inhibiting the degranulation of sensitized mast cells. They prevent the release of various inflammatory mediators, such as **histamine, leukotrienes (LTs), and prostaglandins**, which are triggered by IgE-antigen interactions. They act by inhibiting chloride channels in the mast cell membrane, leading to hyperpolarization and prevention of calcium influx required for degranulation. **2. Why the other options are incorrect:** * **Zileuton:** This is a **5-Lipoxygenase (5-LOX) inhibitor**. It prevents the *synthesis* of leukotrienes from arachidonic acid but does not prevent the release of pre-formed histamine from mast cells. * **Zafirlukast:** This is a **Leukotriene Receptor Antagonist (LTRA)**. It blocks the $CysLT_1$ receptor. It does not prevent the release of mediators; it only blocks the action of leukotrienes at the receptor site. * **Fexofenadine:** This is a **second-generation $H_1$ antihistamine**. It blocks the action of histamine at the receptor level but does not stop the mast cell from releasing it. **High-Yield Clinical Pearls for NEET-PG:** * **Prophylaxis only:** Mast cell stabilizers are used for the *prevention* of bronchial asthma and exercise-induced bronchospasm. They are **ineffective** during an acute attack because they cannot reverse the action of mediators already released. * **Route:** They have poor oral absorption and are typically administered via inhalation (MDI/nebulizer). * **Nedocromil vs. Cromolyn:** Nedocromil is generally considered more potent and may also inhibit the activation of other inflammatory cells like eosinophils and neutrophils.

Question 73: Noscapine is an:

A. Anti-tussive (Correct Answer)
B. Anti-emetic
C. Anti-diarrheal
D. Mucolytic

Explanation: **Explanation:** **Noscapine** is a naturally occurring opium alkaloid belonging to the **benzylisoquinoline** class. Unlike other opioids like morphine or codeine, it lacks analgesic, sedative, or addictive properties. **Why Option A is Correct:** Noscapine acts as a potent **centrally acting anti-tussive**. It works by suppressing the cough reflex through the stimulation of sigma ($\sigma$) receptors in the cough center of the medulla. It is particularly useful in treating non-productive (dry) cough. Unlike codeine, it does not cause constipation or respiratory depression, making it a preferred choice in many proprietary cough formulations. **Why Other Options are Incorrect:** * **B. Anti-emetic:** Noscapine has no action on the Chemoreceptor Trigger Zone (CTZ) or the vomiting center. In fact, like many opium derivatives, high doses may occasionally cause nausea. * **C. Anti-diarrheal:** While opioids like Loperamide or Diphenoxylate are used for diarrhea, Noscapine does not significantly affect intestinal motility. * **D. Mucolytic:** Mucolytics (e.g., Bromhexine, Acetylcysteine) work by breaking down the chemical structure of mucus to reduce its viscosity. Noscapine only suppresses the cough reflex and does not alter mucus rheology. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism:** Centrally acting cough suppressant via sigma receptor agonism. * **Side Effects:** Generally safe, but may cause headache or dizziness. It can release **histamine**, so it should be used with caution in asthmatic patients (may cause bronchoconstriction). * **Unique Fact:** It is a "non-narcotic" opioid; it does not produce euphoria or physical dependence. * **Experimental Use:** It is being researched for potential anti-cancer properties due to its ability to interfere with microtubule assembly (antimitotic).

Question 74: Leukotriene inhibitors are very effective in which one of the following conditions?

A. Exercise-induced asthma
B. Antigen-induced asthma
C. Aspirin-induced asthma (Correct Answer)
D. Occupational asthma

Explanation: **Explanation:** **1. Why Aspirin-induced asthma (AIA) is the correct answer:** Aspirin and other NSAIDs inhibit the enzyme **Cyclooxygenase (COX)**. This inhibition shifts the metabolism of arachidonic acid away from the prostaglandin pathway and toward the **Lipoxygenase (LOX) pathway**. This results in an overproduction of **Cysteinyl Leukotrienes (LTC4, LTD4, LTE4)**, which are potent bronchoconstrictors. Since the pathophysiology of AIA is directly driven by leukotriene excess, Leukotriene Receptor Antagonists (LTRAs) like **Montelukast** and **Zafirlukast** are specifically effective and considered the drugs of choice for managing this condition (Samter’s Triad). **2. Why other options are incorrect:** * **Exercise-induced asthma:** While LTRAs are used for prophylaxis, the primary mechanism involves heat and moisture loss from the airways. Short-acting beta-agonists (SABA) are generally more effective for immediate prevention. * **Antigen-induced asthma:** This is primarily an IgE-mediated Type I hypersensitivity reaction. While leukotrienes are involved, inhaled corticosteroids (ICS) are the mainstay of treatment to control the underlying inflammation. * **Occupational asthma:** This is triggered by specific workplace sensitizers. The most effective management is the removal of the inciting agent; LTRAs are only adjunctive therapy. **3. High-Yield Clinical Pearls for NEET-PG:** * **Mechanism of Action:** Montelukast and Zafirlukast are selective antagonists at the **CysLT1 receptor**. * **Zileuton:** A 5-Lipoxygenase (5-LOX) inhibitor; it is less commonly used due to potential hepatotoxicity. * **Churg-Strauss Syndrome:** A rare but high-yield side effect (eosinophilic granulomatosis with polyangiitis) associated with the use of LTRAs. * **Aspirin Triad (Samter’s Triad):** Consists of Asthma, Aspirin sensitivity, and Nasal polyps.

Question 75: All of the following are used in the management of bronchial asthma, except:

A. Salbutamol
B. Morphine (Correct Answer)
C. Aminophylline
D. Steroids

Explanation: **Explanation:** The correct answer is **Morphine**. In fact, Morphine is strictly **contraindicated** in bronchial asthma. **Why Morphine is the correct answer (Contraindication):** Morphine, an opioid analgesic, is dangerous in asthmatic patients for two primary reasons: 1. **Histamine Release:** Morphine triggers the non-immunologic release of histamine from mast cells, which leads to potent bronchoconstriction and increased mucus secretion, worsening the airway obstruction. 2. **Respiratory Depression:** It acts on the medulla to decrease the sensitivity of the respiratory center to $CO_2$, leading to respiratory depression, which can be fatal during an acute asthma exacerbation. **Why the other options are incorrect:** * **Salbutamol:** A Short-Acting Beta-2 Agonist (SABA). it is the drug of choice for relieving acute bronchospasm by increasing cAMP levels, leading to smooth muscle relaxation. * **Aminophylline:** A methylxanthine (theophylline derivative) that acts by inhibiting phosphodiesterase (PDE) and antagonizing adenosine receptors, resulting in bronchodilation. * **Steroids (Corticosteroids):** These are the mainstay of long-term management. They reduce airway inflammation, decrease mucosal edema, and upregulate beta-2 receptors. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice (Acute Attack):** Inhaled SABA (Salbutamol/Albuterol). * **Drug of Choice (Prophylaxis/Maintenance):** Inhaled Corticosteroids (ICS) like Fluticasone or Budesonide. * **Morphine in Cardiac Asthma:** While contraindicated in bronchial asthma, Morphine is used in **Cardiac Asthma** (secondary to Left Ventricular Failure) because it reduces preload and relieves pulmonary congestion. * **Safe Opioid:** If an opioid is absolutely necessary in an asthmatic patient, **Fentanyl** is preferred as it does not cause histamine release.

Question 76: Which of the following is a vitamin K-dependent clotting factor?

A. Factor 7 (Correct Answer)
B. Factor 1
C. Factor 11
D. Factor 12

Explanation: Vitamin K is an essential cofactor for the post-translational modification of specific clotting factors [1]. Specifically, it is required for the **gamma-carboxylation of glutamate residues** on these proteins, which allows them to bind calcium and adhere to phospholipid surfaces during the coagulation cascade [2]. **Why Option A is Correct:** The Vitamin K-dependent clotting factors are **Factors II (Prothrombin), VII, IX, and X** [1, 2], as well as the anticoagulant proteins **Protein C and Protein S** [2, 3]. Factor VII has the shortest half-life (approx. 6 hours) among these, making it the first factor to decline when Vitamin K is deficient or when Warfarin therapy is initiated. **Why Other Options are Incorrect:** * **Option B (Factor I):** Also known as Fibrinogen, it is a soluble plasma protein converted to fibrin by thrombin. Its synthesis is not dependent on Vitamin K. * **Option C (Factor XI):** Part of the intrinsic pathway (Plasma Thromboplastin Antecedent). It is synthesized in the liver but does not require gamma-carboxylation. * **Option D (Factor XII):** Known as Hageman factor, it initiates the intrinsic pathway upon contact with negatively charged surfaces. It is not Vitamin K-dependent. **High-Yield Clinical Pearls for NEET-PG:** * **Warfarin Mechanism:** Inhibits **Vitamin K Epoxide Reductase (VKOR)**, preventing the recycling of Vitamin K [3]. * **Monitoring:** Prothrombin Time (PT/INR) is used to monitor Warfarin because it is most sensitive to changes in **Factor VII**. * **Antidote:** For immediate reversal of Warfarin-induced bleeding, use **Fresh Frozen Plasma (FFP)** or Prothrombin Complex Concentrate (PCC). For non-emergent reversal, use Vitamin K1 (Phytonadione).

Question 77: Montelukast is:

A. Leukotriene antagonist (Correct Answer)
B. Potassium channel opener
C. Smooth muscle relaxant
D. Anti-inflammatory

Explanation: **Explanation:** **Correct Option: A. Leukotriene antagonist** Montelukast is a selective and competitive antagonist of the **CysLT1 receptor** (Cysteinyl Leukotriene receptor 1). In the pathogenesis of asthma, leukotrienes (LTC4, LTD4, and LTE4) are potent inflammatory mediators released from mast cells and eosinophils. They cause intense bronchoconstriction, increased mucus secretion, and mucosal edema. By blocking these receptors, Montelukast prevents these effects, making it an effective "controller" medication for chronic asthma and allergic rhinitis. **Analysis of Incorrect Options:** * **B. Potassium channel opener:** These drugs (e.g., Nicorandil, Minoxidil) cause hyperpolarization of smooth muscle cells leading to vasodilation. They are used in angina or hypertension, not as a primary mechanism for Montelukast. * **C. Smooth muscle relaxant:** While Montelukast results in bronchodilation, it is classified by its specific molecular target (Leukotriene receptor). Direct smooth muscle relaxants include Beta-2 agonists (Salbutamol) or Methylxanthines (Theophylline). * **D. Anti-inflammatory:** While Montelukast has modest anti-inflammatory properties, it is not categorized as a primary anti-inflammatory agent like Corticosteroids. In pharmacology exams, its specific mechanism (Leukotriene antagonism) always takes precedence. **NEET-PG High-Yield Pearls:** * **Clinical Use:** It is the drug of choice for **Aspirin-Induced Asthma** and **Exercise-Induced Bronchospasm**. * **Administration:** It is administered **orally**, usually once daily in the evening. * **Side Effects:** Recently, the FDA issued a boxed warning regarding **neuropsychiatric events** (e.g., agitation, sleep disturbances, suicidal ideation). * **Comparison:** Unlike Zileuton (which inhibits the 5-LOX enzyme), Montelukast and Zafirlukast block the receptor itself.

Question 78: Omaiizumab is used for which of the following conditions?

A. Rheumatoid arthritis
B. Asthma (Correct Answer)
C. Prostate cancer
D. CLL

Explanation: **Explanation:** **Correct Answer: B. Asthma** **Mechanism of Action:** Omalizumab is a **recombinant DNA-derived humanized monoclonal antibody** that selectively binds to free human **Immunoglobulin E (IgE)** in the blood and interstitial fluid. By binding to the Fc region of IgE, it prevents IgE from attaching to the high-affinity IgE receptors (FcεRI) on the surface of **mast cells and basophils**. This prevents the release of inflammatory mediators (like histamine and leukotrienes) that trigger an asthma exacerbation. **Why other options are incorrect:** * **A. Rheumatoid Arthritis:** This is typically treated with TNF-alpha inhibitors (e.g., Infliximab, Adalimumab) or IL-6 inhibitors (e.g., Tocilizumab). * **C. Prostate Cancer:** Advanced cases are treated with hormonal therapy (e.g., Abiraterone, Enzalutamide) or chemotherapy, not IgE blockers. * **D. CLL (Chronic Lymphocytic Leukemia):** This is treated with anti-CD20 antibodies like **Rituximab** or BTK inhibitors like Ibrutinib. **High-Yield Clinical Pearls for NEET-PG:** * **Indication:** It is specifically used for **moderate-to-severe persistent allergic asthma** in patients (≥6 years) who are inadequately controlled with inhaled corticosteroids. * **Route:** Administered **subcutaneously** every 2 to 4 weeks. * **Key Side Effect:** The most serious (though rare) side effect is **anaphylaxis**; patients must be monitored post-injection. * **Diagnostic Requirement:** Before starting Omalizumab, a skin test or RAST must be positive for a perennial aeroallergen, and serum IgE levels must be elevated.

Question 79: What is the mechanism of action of Salmeterol?

A. Pure beta-2 agonist (Correct Answer)
B. Pure beta-1 agonist
C. Beta-1 and Beta-2 agonist
D. Alpha-1 agonist

Explanation: **Explanation:** **Salmeterol** is a Long-Acting Beta-2 Agonist (LABA) used primarily in the maintenance treatment of asthma and COPD. Its mechanism of action involves the selective stimulation of **Beta-2 receptors** located on the bronchial smooth muscle. This stimulation activates the enzyme adenylyl cyclase, increasing intracellular cyclic AMP (cAMP), which leads to powerful bronchodilation. **Why Option A is Correct:** Salmeterol is classified as a **selective (pure) Beta-2 agonist**. Unlike short-acting agents (SABA) like Salbutamol, Salmeterol has a long lipophilic side chain that anchors it to the receptor site, providing a prolonged duration of action (approx. 12 hours). **Why Other Options are Incorrect:** * **Option B & C:** Beta-1 receptors are primarily located in the heart. Stimulation causes increased heart rate (tachycardia) and contractility. While selectivity is lost at very high doses, Salmeterol is designed to avoid Beta-1 activation to minimize cardiac side effects. * **Option D:** Alpha-1 agonists cause vasoconstriction and are used as nasal decongestants (e.g., Oxymetazoline) or to raise blood pressure, not for bronchodilation. **High-Yield Clinical Pearls for NEET-PG:** * **Onset vs. Duration:** Salmeterol has a **slow onset of action**; therefore, it is never used for acute asthma attacks (Rescue therapy). It is for maintenance only. * **Black Box Warning:** LABAs should **never be used as monotherapy** in asthma due to the risk of asthma-related death. They must always be combined with an Inhaled Corticosteroid (ICS). * **Side Effects:** Fine tremors (skeletal muscle Beta-2 stimulation), tachycardia (reflex or Beta-1 crossover), and hypokalemia.

Question 80: Which of the following expectorants causes gastric irritation and a reflex increase in bronchial gland secretions?

A. Ambroxol
B. Guaifenesin (Correct Answer)
C. Sodium cromoglycate
D. Fosaprepitant

Explanation: ### Explanation **Correct Option: B. Guaifenesin** Guaifenesin is a classic **secretolytic expectorant**. Its primary mechanism of action involves **gastric irritation**, which stimulates the vagal afferent nerves in the stomach lining. This triggers a **reflex increase in bronchial gland secretions** (efferent parasympathetic response). By increasing the volume and decreasing the viscosity of respiratory tract fluid, it makes the mucus thinner and easier to expel via coughing. **Analysis of Incorrect Options:** * **A. Ambroxol:** This is a **mucolytic** agent (a metabolite of Bromhexine). It works by breaking down the acid mucopolysaccharide fibers in the sputum and stimulating surfactant production. It does not primarily act via the gastric reflex mechanism. * **C. Sodium cromoglycate:** This is a **mast cell stabilizer** used in the prophylaxis of bronchial asthma. It prevents the degranulation of mast cells and the release of inflammatory mediators like histamine. It has no expectorant properties. * **D. Fosaprepitant:** This is a **Neurokinin-1 (NK1) receptor antagonist** used as an antiemetic, specifically for chemotherapy-induced nausea and vomiting (CINV). It has no role in the respiratory system. **High-Yield NEET-PG Pearls:** * **Classification of Expectorants:** 1. **Directly acting:** Volatile oils (e.g., Eucalyptus oil), Potassium iodide (secreted by bronchial glands). 2. **Reflexly acting:** Guaifenesin, Ammonium salts, Sodium/Potassium citrate. * **Mucolytics vs. Expectorants:** Mucolytics (Acetylcysteine, Carbocisteine, Bromhexine) chemically alter the mucus structure, whereas expectorants increase the volume of secretion to facilitate removal. * **Acetylcysteine:** Acts by breaking **disulfide bonds** in mucoproteins; it is also the specific antidote for **Paracetamol (Acetaminophen) poisoning**.

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