Respiratory System Drugs — MCQs

Respiratory System Drugs Indian Medical PG Practice Questions and MCQs

Question 11: FDA approved the use of modafinil as an adjunct in which of the following conditions?

A. Sleep apnea (Correct Answer)
B. Narcolepsy
C. Depression with lethargy
D. Tourette's syndrome

Explanation: **Explanation:** **Modafinil** is a non-amphetamine wakefulness-promoting agent. While its exact mechanism is not fully elucidated, it is believed to inhibit dopamine reuptake and increase hypothalamic levels of orexin and histamine, leading to increased alertness. **Why Sleep Apnea is the Correct Answer:** The FDA has specifically approved modafinil as an **adjunctive (add-on) therapy** for **Obstructive Sleep Apnea (OSA)**. In these patients, modafinil is used to treat residual excessive daytime sleepiness (EDS) that persists despite optimal treatment of the underlying airway obstruction with Continuous Positive Airway Pressure (CPAP). It does not treat the cause of apnea but improves the patient's quality of life and alertness. **Analysis of Incorrect Options:** * **B. Narcolepsy:** While modafinil is a **first-line treatment** for narcolepsy, the question specifically asks for its use as an **adjunct**. In narcolepsy, it is typically used as primary monotherapy for daytime somnolence. * **C. Depression with lethargy:** Modafinil is sometimes used "off-label" to treat fatigue associated with depression or multiple sclerosis, but it is not FDA-approved for this indication. * **D. Tourette's syndrome:** Modafinil has no role in Tourette’s; in fact, stimulants can sometimes exacerbate tics. **High-Yield Clinical Pearls for NEET-PG:** * **FDA Approved Indications:** Narcolepsy, Shift Work Sleep Disorder, and Adjunct in OSA. * **Side Effects:** Headache (most common), nausea, and nervousness. Rarely, it can cause serious skin reactions like **Stevens-Johnson Syndrome (SJS)**. * **Advantage over Amphetamines:** It has a lower potential for abuse, less peripheral sympathomimetic stimulation (less tachycardia/hypertension), and less "rebound" hypersomnolence. * **Armodafinil:** The R-enantiomer of modafinil with a longer half-life.

Question 12: Which humanized monoclonal antibody binds IgE to prevent its binding to the high-affinity IgE receptor, thereby blocking IgE-mediated allergic response and inflammation in bronchial asthma?

A. Palivizumab
B. Natalizumab
C. Omalizumab (Correct Answer)
D. Etilizumab

Explanation: **Explanation:** **Omalizumab** is a recombinant DNA-derived humanized monoclonal antibody specifically designed for the management of moderate-to-severe persistent allergic asthma. **Mechanism of Action:** Omalizumab binds selectively to the **Fc region of free circulating IgE**. By doing so, it prevents IgE from binding to the high-affinity IgE receptors (**FcεRI**) located on the surface of mast cells and basophils. This prevents the cross-linking of IgE by allergens, thereby inhibiting the release of inflammatory mediators (histamine, leukotrienes) that cause bronchoconstriction and airway inflammation. It also downregulates the expression of FcεRI receptors over time. **Analysis of Incorrect Options:** * **Palivizumab (A):** A monoclonal antibody directed against the **F protein of Respiratory Syncytial Virus (RSV)**. It is used for the prevention of RSV infections in high-risk infants. * **Natalizumab (B):** An anti-integrin antibody that binds to **α4-integrin**. It is used in the treatment of Multiple Sclerosis and Crohn’s disease by preventing leukocyte migration into tissues. * **Etilizumab (D):** This is not a standard drug used in respiratory pharmacology; it is likely a distractor. **High-Yield Clinical Pearls for NEET-PG:** * **Route:** Administered **Subcutaneously** every 2–4 weeks. * **Indication:** Step 5 or 6 of GINA guidelines for patients with high serum IgE levels not controlled by high-dose ICS + LABA. * **Side Effect:** The most serious (though rare) side effect is **anaphylaxis**; patients should be monitored post-injection. * **Other Biologicals in Asthma:** * **Mepolizumab/Reslizumab:** Anti-IL-5 (for eosinophilic asthma). * **Benralizumab:** Anti-IL-5 Receptor alpha. * **Dupilumab:** Anti-IL-4 Receptor alpha (inhibits IL-4 and IL-13).

Question 13: Zafirlukast used in asthmatic patients acts by?

A. Phosphodiesterase inhibition
B. Endothelium receptor blockage
C. Leukotriene receptor blockage (Correct Answer)
D. Lipoxygenase inhibitor

Explanation: **Explanation:** **Correct Answer: C. Leukotriene receptor blockage** Zafirlukast and Montelukast are **selective and competitive antagonists** of the **CysLT1 receptor** (Cysteinyl Leukotriene receptor 1). In asthma, leukotrienes (LTC4, LTD4, and LTE4) are potent bronchoconstrictors and mediators of inflammation. By blocking these receptors, Zafirlukast prevents airway edema, smooth muscle contraction, and the inflammatory response, making it an effective "controller" medication for prophylaxis. **Analysis of Incorrect Options:** * **A. Phosphodiesterase (PDE) inhibition:** This is the mechanism of **Theophylline** (non-selective PDE inhibitor) and **Roflumilast** (selective PDE4 inhibitor). These drugs increase intracellular cAMP, leading to bronchodilation. * **B. Endothelium receptor blockage:** This likely refers to Endothelin receptor antagonists like **Bosentan**, which are used in the treatment of Pulmonary Arterial Hypertension (PAH), not bronchial asthma. * **D. Lipoxygenase inhibitor:** This refers to **Zileuton**, which inhibits the 5-Lipoxygenase (5-LOX) enzyme, thereby preventing the *synthesis* of leukotrienes rather than blocking their receptors. **High-Yield Clinical Pearls for NEET-PG:** * **Indications:** Used for chronic asthma prophylaxis and aspirin-induced asthma. They are **not** effective for acute asthma attacks. * **Montelukast vs. Zafirlukast:** Montelukast is preferred as it is taken once daily and does not inhibit CYP enzymes. * **Side Effects:** Zafirlukast can cause a rare elevation in liver enzymes and is associated with **Churg-Strauss syndrome** (eosinophilic granulomatosis with polyangiitis) upon withdrawal of systemic steroids. * **Drug Interaction:** Zafirlukast inhibits CYP2C9 and CYP3A4, potentially increasing Warfarin levels.

Question 14: Which opioid analgesic is used in the treatment of cough?

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

Explanation: **Explanation:** **Codeine** is the correct answer because it is a prototypical **opioid antitussive**. It acts centrally by suppressing the cough center in the medulla oblongata. It is highly effective for dry, non-productive coughs at sub-analgesic doses. While it carries a risk of constipation and mild sedation, it remains the gold standard against which other antitussives are compared. **Analysis of Options:** * **Noscapine (Option A):** While used as an antitussive, it is an alkaloid derived from opium but is **non-narcotic/non-opioid** in nature. It does not have analgesic or addicting properties and acts by suppressing the cough reflex without affecting the CNS like opioids. * **Dextromethorphan (Option B):** This is a synthetic derivative of morphine (the d-isomer of levorphanol). However, it is classified as a **non-opioid antitussive** because it does not act on opioid receptors (it acts on NMDA and sigma receptors) and lacks analgesic or addictive potential. * **Meperidine (Option D):** Also known as Pethidine, this is a potent opioid analgesic used for acute pain and shivering. It has **no significant antitussive activity** and is not used in respiratory medicine. **High-Yield Clinical Pearls for NEET-PG:** * **Codeine** is contraindicated in children under 12 years (and up to 18 years post-tonsillectomy) due to the risk of ultra-rapid metabolism to morphine, leading to fatal respiratory depression. * **Pholcodine** is another opioid antitussive with a longer duration of action than codeine. * **Benzonatate** is a peripherally acting antitussive that works by anesthetizing stretch receptors in the lungs. * For a productive cough, antitussives are generally avoided; **expectorants** (e.g., Guaifenesin) or **mucolytics** (e.g., Bromhexine, Acetylcysteine) are preferred.

Question 15: Which of the following is very effective in the management of acute exacerbation of asthma and status asthmaticus?

A. Beclomethasone
B. Budesonide
C. Ciclesonide
D. None of the above (Correct Answer)

Explanation: ### Explanation The correct answer is **None of the above** because all the listed options (Beclomethasone, Budesonide, and Ciclesonide) are **Inhaled Corticosteroids (ICS)**. #### 1. Why the correct answer is right In the management of **acute exacerbation of asthma** and **status asthmaticus**, the primary goal is to achieve rapid bronchodilation and systemic anti-inflammatory effects. Inhaled corticosteroids have a slow onset of action (taking days to weeks for full effect) and are used for **prophylaxis/maintenance therapy**, not for emergency relief. For status asthmaticus, the gold standard treatment includes: * **Systemic Corticosteroids:** Intravenous (IV) Hydrocortisone or Methylprednisolone, or Oral Prednisolone. * **Short-Acting Beta-2 Agonists (SABA):** Salbutamol (nebulized). * **Anticholinergics:** Ipratropium bromide. * **Oxygen therapy** and potentially IV Magnesium Sulfate. #### 2. Why the incorrect options are wrong * **Beclomethasone & Budesonide:** These are standard ICS used for long-term control of chronic asthma. They lack the rapid systemic distribution required to reverse the severe airway inflammation seen in status asthmaticus. * **Ciclesonide:** This is a **prodrug** activated by esterases in the bronchial epithelium. While it has fewer systemic side effects (like oropharyngeal candidiasis), its slow onset makes it entirely unsuitable for acute emergencies. #### 3. NEET-PG High-Yield Pearls * **Drug of Choice (DOC) for Status Asthmaticus:** Nebulized Salbutamol + Ipratropium + Systemic Corticosteroids (IV Hydrocortisone). * **Ciclesonide:** Known for having the highest topical-to-systemic potency ratio and minimal oral bioavailability. * **Status Asthmaticus Definition:** A severe, life-threatening asthma attack that does not respond to standard treatment with bronchodilators. * **Inhaled Steroid Side Effects:** Most common is oropharyngeal candidiasis (prevented by using a spacer and rinsing the mouth).

Question 16: Which oral and topical drug is used for nasal decongestion?

A. Phenylephrine (Correct Answer)
B. Histamine
C. Methoxamine
D. Dopamine

Explanation: **Explanation:** **Phenylephrine** is the correct answer because it is a selective **$\alpha_1$-adrenergic agonist**. Its primary mechanism of action involves stimulating $\alpha_1$ receptors on the vascular smooth muscle of the nasal mucosa, leading to **vasoconstriction**. This reduces mucosal edema and nasal stuffiness. It is unique among the options as it is available in both **topical** (nasal drops/sprays) and **oral** formulations (often found in multi-symptom cold medicines). **Analysis of Incorrect Options:** * **Histamine:** This is a mediator of inflammation and allergy. It causes vasodilation and increased capillary permeability, which actually *worsens* nasal congestion and causes rhinorrhea. * **Methoxamine:** While it is a selective $\alpha_1$ agonist, it is primarily used parenterally to treat hypotension during anesthesia. It is not used clinically as a nasal decongestant. * **Dopamine:** This is a catecholamine used in emergency settings for cardiogenic shock or acute heart failure. It acts on $D_1$, $\beta_1$, and $\alpha_1$ receptors (at high doses) but has no role in treating nasal congestion. **High-Yield Clinical Pearls for NEET-PG:** * **Rhinitis Medicamentosa:** Prolonged use of topical decongestants (usually >3–5 days) like Phenylephrine or Oxymetazoline can lead to **rebound congestion** due to down-regulation of receptors. * **Systemic Effects:** Oral Phenylephrine should be used with caution in patients with **Hypertension** and **Benign Prostatic Hyperplasia (BPH)**, as $\alpha_1$ stimulation can increase blood pressure and urinary retention. * **Other Decongestants:** **Pseudoephedrine** is another common oral decongestant, but it is a non-selective sympathomimetic.

Question 17: In a patient experiencing an acute exacerbation of asthma, salbutamol was administered with no improvement. Subsequent treatment with intravenous corticosteroids and aminophylline led to clinical improvement. What is the primary mechanism of action of corticosteroids in managing acute asthma?

A. Corticosteroids increase bronchial responsiveness to bronchodilators like salbutamol. (Correct Answer)
B. Corticosteroids provide direct bronchodilation, particularly when used in conjunction with xanthines.
C. Corticosteroids indirectly enhance the effects of xanthines by acting on adenosine receptors.
D. Corticosteroids improve mucociliary clearance, contributing to symptom relief.

Explanation: ### Explanation **1. Why Option A is Correct:** Corticosteroids do not possess direct bronchodilatory properties. Their primary utility in acute asthma stems from their ability to **upregulate and sensitize $\beta_2$-adrenergic receptors**. In chronic or severe asthma, $\beta_2$-receptors often become "downregulated" or desensitized due to inflammation or overuse of SABA (Short-Acting Beta-Agonists). Corticosteroids increase the transcription of $\beta_2$-receptor genes in the airway, thereby restoring and enhancing the bronchial responsiveness to drugs like Salbutamol. Additionally, they reduce airway edema and mucosal inflammation by inhibiting the recruitment of inflammatory cells and the release of cytokines. **2. Why Other Options are Incorrect:** * **Option B:** Corticosteroids have **no direct relaxant effect** on bronchial smooth muscle. Their effect is genomic and takes several hours (4–6 hours) to manifest. * **Option C:** Corticosteroids do not act on adenosine receptors. Aminophylline (a methylxanthine) works by inhibiting phosphodiesterase (PDE) and antagonizing adenosine receptors; corticosteroids do not mediate this pathway. * **Option D:** While corticosteroids may indirectly reduce mucus plug formation by decreasing inflammation, this is not their *primary* mechanism for reversing an acute exacerbation compared to the restoration of $\beta_2$ responsiveness. **3. NEET-PG High-Yield Pearls:** * **Lag Period:** Always remember that IV/Oral steroids take **4–12 hours** to show clinical benefit; they are not for "instant" relief but for preventing relapse and resolving inflammation. * **Synergy:** The combination of steroids and $\beta_2$-agonists is synergistic (Steroids increase $\beta_2$ receptors; $\beta_2$-agonists activate the steroid receptors). * **Drug of Choice:** For acute severe asthma (Status Asthmaticus), the first-line treatment is **Inhaled SABA + Ipratropium bromide + Systemic Corticosteroids.** * **Mechanism:** Corticosteroids inhibit **Phospholipase $A_2$**, leading to decreased production of leukotrienes and prostaglandins.

Question 18: A diabetic female on isoniazid and rifampicin for tuberculosis developed deep vein thrombosis. She was started on warfarin. Her prothrombin time is not raised. What should be the next step in management?

A. Increase the dose of warfarin
B. Replace warfarin with acenocoumarol
C. Switch ethambutol for rifampicin
D. Use low molecular weight heparin (Correct Answer)

Explanation: ### Explanation **1. Why the correct answer is right:** The patient is taking **Rifampicin**, which is a potent **microsomal enzyme inducer** (specifically CYP3A4 and CYP2C9). Warfarin is metabolized by these enzymes. Rifampicin significantly increases the metabolism of warfarin, leading to a failure to achieve therapeutic anticoagulation (as evidenced by the unchanged prothrombin time). In a patient with active Deep Vein Thrombosis (DVT), immediate and reliable anticoagulation is required. **Low Molecular Weight Heparin (LMWH)** is the drug of choice here because its metabolism is independent of the cytochrome P450 system, ensuring a predictable anticoagulant effect despite the presence of Rifampicin. **2. Why the incorrect options are wrong:** * **A. Increase the dose of warfarin:** While theoretically possible, the induction by Rifampicin is so potent that extremely high doses of warfarin would be needed, making the INR highly unstable and difficult to monitor. * **B. Replace warfarin with acenocoumarol:** Acenocoumarol is also a Vitamin K antagonist metabolized by the liver; it would face the same enzyme induction issues as warfarin. * **C. Switch ethambutol for rifampicin:** Rifampicin is a "sterilizing" drug and a cornerstone of Anti-Tubercular Therapy (ATT). It cannot be stopped or substituted with a less potent drug like ethambutol simply to facilitate warfarin use, as this risks treatment failure and drug resistance. **3. Clinical Pearls for NEET-PG:** * **Rifampicin Interactions:** "Rifampicin **R**amps up enzymes." It decreases the efficacy of OCPs, Warfarin, Digoxin, and Sulfonylureas. * **Isoniazid (INH):** Unlike Rifampicin, INH is an enzyme **inhibitor**. However, in combination therapy, the inducing effect of Rifampicin usually dominates. * **LMWH vs. Heparin:** LMWH (e.g., Enoxaparin) is preferred over Unfractionated Heparin due to a longer half-life, subcutaneous administration, and no requirement for routine PTT monitoring. * **Warfarin Monitoring:** Monitored by **PT/INR** (Extrinsic pathway). Heparin is monitored by **aPTT** (Intrinsic pathway).

Question 19: Megaloblastic anemia may be caused by all of the following except?

A. Dilantin toxicity
B. Vitamin B12 deficiency
C. Folic acid deficiency
D. Long term aspirin intake (Correct Answer)

Explanation: Megaloblastic anemia is characterized by impaired DNA synthesis, leading to the presence of large, nucleated red blood cell precursors (megaloblasts) in the bone marrow [1]. **Why Long-term Aspirin is the Correct Answer:** Aspirin (Acetylsalicylic acid) is a non-steroidal anti-inflammatory drug (NSAID) that inhibits cyclooxygenase (COX) enzymes. While chronic aspirin use is associated with **Iron Deficiency Anemia** (due to occult gastrointestinal bleeding), it does not interfere with DNA synthesis or folate/B12 metabolism. Therefore, it does not cause megaloblastic anemia. **Analysis of Incorrect Options:** * **Vitamin B12 & Folic Acid Deficiency:** These are the most common causes [3]. B12 and Folate are essential co-factors for DNA synthesis [2]. Deficiency leads to "nuclear-cytoplasmic asynchrony," where the nucleus matures slower than the cytoplasm. * **Dilantin (Phenytoin) Toxicity:** Phenytoin is a notorious cause of drug-induced megaloblastic anemia. It interferes with folate metabolism by inhibiting the intestinal enzyme (folate conjugase) required for folate absorption and by increasing folate catabolism. **NEET-PG High-Yield Pearls:** * **Drug-Induced Megaloblastic Anemia (Mnemonic: "M-P-S-T"):** * **M**ethotrexate (Dihydrofolate reductase inhibitor) * **P**henytoin/Pyrimethamine * **S**ulfa drugs (Trimethoprim) * **T**rimethoprim * **Zidovudine (AZT):** A common cause of macrocytosis (increased MCV) without necessarily causing full megaloblastic changes. * **Nitrous Oxide:** Can cause acute megaloblastic anemia by oxidizing the cobalt atom in Vitamin B12, rendering it inactive.

Question 20: Which of the following antiasthma drugs is not a bronchodilator?

A. Ipratropium bromide
B. Theophylline
C. Sodium cromoglycate (Correct Answer)
D. Formoterol

Explanation: **Explanation:** The management of bronchial asthma involves two main categories of drugs: **Bronchodilators** (which provide symptomatic relief by relaxing airway smooth muscle) and **Anti-inflammatory agents/Mast cell stabilizers** (which prevent attacks but do not reverse bronchoconstriction). **Why Sodium Cromoglycate is the correct answer:** Sodium cromoglycate is a **Mast Cell Stabilizer**. It works by inhibiting the degranulation of mast cells triggered by IgE-antigen interactions, thereby preventing the release of inflammatory mediators like histamine and leukotrienes. It is used for **prophylaxis** only; it has no direct relaxant effect on bronchial smooth muscle and is, therefore, **not a bronchodilator**. It is ineffective during an acute attack of asthma. **Analysis of Incorrect Options:** * **A. Ipratropium bromide:** An **Anticholinergic (Muscarinic antagonist)**. It blocks M3 receptors in the bronchial smooth muscle, leading to bronchodilation. It is particularly useful in COPD and as an adjunct in acute asthma. * **B. Theophylline:** A **Methylxanthine**. It causes bronchodilation by inhibiting the enzyme phosphodiesterase (PDE), leading to increased levels of cAMP, and by antagonizing adenosine receptors. * **D. Formoterol:** A **Long-Acting Beta-2 Agonist (LABA)**. It stimulates $\beta_2$ receptors, increasing cAMP and causing potent bronchodilation. **NEET-PG High-Yield Pearls:** * **Drug of choice for Acute Asthma:** Salbutamol (SABA). * **Drug of choice for Exercise-induced Asthma:** Cromolyn sodium (if taken prophylactic) or Salbutamol. * **Nedocromil:** Another mast cell stabilizer similar to Sodium cromoglycate but with better efficacy in reducing bronchial hyperreactivity. * **Side effect of Sodium cromoglycate:** Throat irritation, cough, and rarely, bronchospasm (paradoxical).

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

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