Respiratory System Drugs — MCQs

Respiratory System Drugs Indian Medical PG Practice Questions and MCQs

Question 91: A child diagnosed with cystic fibrosis was prescribed an inhaled agent to dissolve mucus plugging the airways. This agent is also used as an antidote to reverse the toxicity of which drugs?

A. Aspirin
B. Acetaminophen (Correct Answer)
C. Heparin
D. Streptokinase

Explanation: ### Explanation The drug described is **N-acetylcysteine (NAC)**. In cystic fibrosis, NAC acts as a **mucolytic** by breaking the disulfide bonds in mucoproteins, thereby reducing the viscosity of mucus and facilitating its clearance from the airways. **Why Acetaminophen is correct:** N-acetylcysteine is the specific antidote for **Acetaminophen (Paracetamol) toxicity**. * **Mechanism:** Acetaminophen overdose leads to the depletion of glutathione stores and the accumulation of the toxic metabolite **NAPQI**. * **Action:** NAC acts as a precursor for **glutathione** synthesis and can also directly bind to NAPQI, neutralizing its hepatotoxic effects. It is most effective when administered within 8–10 hours of ingestion. **Why other options are incorrect:** * **Aspirin:** Toxicity is managed with gastric lavage, activated charcoal, and **urinary alkalinization** (using Sodium Bicarbonate) to enhance excretion. * **Heparin:** The specific antidote for heparin overdose is **Protamine sulfate**, which neutralizes heparin through ionic binding. * **Streptokinase:** Bleeding caused by thrombolytics like streptokinase is managed using antifibrinolytics such as **Epsilon-aminocaproic acid** or **Tranexamic acid**. **High-Yield Clinical Pearls for NEET-PG:** * **NAC Administration:** In acetaminophen poisoning, the **Rumack-Matthew Nomogram** is used to determine the need for NAC based on plasma levels. * **Other uses of NAC:** It is used to prevent **Contrast-Induced Nephropathy (CIN)** and as an adjuvant in treating hemorrhagic cystitis caused by Cyclophosphamide. * **Route:** For mucolysis, it is inhaled; for toxicity, it can be given orally or intravenously.

Question 92: What is the mechanism of action of antitussives?

A. Raise the threshold of the cough center (Correct Answer)
B. Inhibition of the breathing center
C. Inhibition of the respiratory center
D. Increase tussal impulses

Explanation: **Explanation:** **Mechanism of Action:** Antitussives (cough suppressants) act primarily on the central nervous system. Their core mechanism is to **raise the threshold of the cough center** located in the medulla oblongata. By increasing this threshold, these drugs reduce the sensitivity of the center to afferent impulses coming from the respiratory tract. Consequently, it takes a much stronger stimulus to trigger the cough reflex, thereby reducing the frequency and intensity of a dry, non-productive cough. **Analysis of Options:** * **Option A (Correct):** As explained, they blunt the reflex arc by making the medullary cough center less responsive. * **Option B & C (Incorrect):** While some opioid antitussives (like Codeine or Morphine) can cause respiratory depression at high doses, their therapeutic goal is *not* to inhibit the breathing or respiratory centers. Selective antitussives aim to suppress the cough reflex without significantly affecting the rhythmic drive of respiration. * **Option D (Incorrect):** Increasing tussal impulses would exacerbate coughing. Antitussives aim to decrease the transmission or perception of these impulses. **NEET-PG High-Yield Pearls:** * **Classification:** * **Opioids:** Codeine (standard antitussive), Pholcodine. * **Non-opioids:** Noscapine, Dextromethorphan (most common; acts on NMDA receptors; no analgesic/addictive property). * **Peripherally acting:** Benzonatate (anesthetizes stretch receptors in the lungs). * **Clinical Contraindication:** Antitussives should **not** be used in productive (wet) coughs, as suppressing the cough reflex leads to sputum retention, which can cause airway obstruction and secondary infections. * **Drug of Choice:** Dextromethorphan is often preferred over codeine due to its lack of constipating and addictive side effects.

Question 93: What is the drug of choice for Type 1 Brittle asthma?

A. Subcutaneous salbutamol
B. Subcutaneous terbutaline (Correct Answer)
C. Subcutaneous adrenaline
D. Subcutaneous mometasone

Explanation: **Explanation:** **Brittle Asthma** is a rare but severe form of difficult-to-treat asthma characterized by wide variations in Peak Expiratory Flow (PEF) despite high-dose inhaled therapy. It is categorized into two types: * **Type 1:** Persistent, chaotic variability in PEF (diurnal variation >40%). * **Type 2:** Sudden, life-threatening drops in PEF on a background of otherwise well-controlled asthma. **Why Subcutaneous Terbutaline is the Correct Answer:** For patients with **Type 1 Brittle Asthma** who remain symptomatic despite maximal inhaled therapy (including high-dose steroids and long-acting beta-agonists), a **continuous subcutaneous infusion of Terbutaline** is the established drug of choice. Terbutaline, a $\beta_2$-agonist, provides a steady systemic bronchodilatory effect, bypassing the limitations of inhaled delivery in patients with severe airway remodeling or poor inhalation technique during fluctuations. **Analysis of Incorrect Options:** * **Subcutaneous Salbutamol:** While also a $\beta_2$-agonist, Terbutaline is preferred in clinical guidelines for continuous subcutaneous infusion due to its established efficacy and safety profile in this specific delivery mode. * **Subcutaneous Adrenaline:** This is the drug of choice for **Anaphylaxis** and may be used in acute severe asthma (Status Asthmaticus) if IM/IV access is difficult, but it is not used for the long-term management of brittle asthma due to non-selective $\alpha$ and $\beta_1$ side effects. * **Subcutaneous Mometasone:** Mometasone is a corticosteroid used via inhalation or intranasal routes. There is no subcutaneous formulation used for asthma management. **High-Yield NEET-PG Pearls:** * **Drug of Choice for Acute Severe Asthma:** Inhaled Salbutamol (SABA) + Ipratropium bromide. * **Drug of Choice for Exercise-induced Asthma:** Inhaled SABA (Salbutamol) taken 15–20 minutes before exercise. * **Magnesium Sulfate:** Used intravenously in life-threatening asthma non-responsive to initial bronchodilators. * **Omalizumab:** An anti-IgE antibody used for severe allergic asthma.

Question 94: All of the following drugs are useful in the treatment of a patient with acute bronchial asthma EXCEPT?

A. Ipratropium
B. Salbutamol
C. Montelukast (Correct Answer)
D. Hydrocortisone

Explanation: ### Explanation The management of **acute bronchial asthma** focuses on rapid reversal of airway obstruction and reduction of inflammation. **Why Montelukast is the Correct Answer:** Montelukast is a **Leukotriene Receptor Antagonist (LTRA)**. While it is highly effective for the **prophylaxis** and chronic management of asthma (especially aspirin-induced and exercise-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 Incorrect Options:** * **Salbutamol (Option B):** A Short-Acting Beta-2 Agonist (SABA). It is the **drug of choice** for acute asthma due to its rapid onset (2–5 minutes) of bronchodilation via cAMP stimulation. * **Ipratropium (Option A):** A Short-Acting Muscarinic Antagonist (SAMA). It is used as an adjunct to SABAs in acute severe asthma to provide additional bronchodilation by blocking vagal-mediated bronchoconstriction. * **Hydrocortisone (Option D):** A systemic corticosteroid. It is used in acute attacks to reduce airway inflammation and upregulate beta-receptors. While it takes 4–6 hours to act, it is vital for preventing relapse and managing "status asthmaticus." **Clinical Pearls for NEET-PG:** * **Drug of Choice (Acute):** Inhaled Salbutamol. * **Drug of Choice (Prophylaxis/Chronic):** Inhaled Corticosteroids (e.g., Fluticasone). * **Aspirin-Induced Asthma:** LTRAs (Montelukast/Zafirlukast) are the preferred treatment. * **Magnesium Sulfate:** Used intravenously in life-threatening asthma non-responsive to initial therapy.

Question 95: Methylxanthines exert the following action(s) at cellular/molecular level:

A. Intracellular release of Ca2+
B. Inhibition of phosphodiesterase
C. Antagonism of adenosine
D. All of the above (Correct Answer)

Explanation: **Explanation:** Methylxanthines (such as **Theophylline** and **Aminophylline**) are bronchodilators that work through multiple synergistic mechanisms at the cellular level: 1. **Inhibition of Phosphodiesterase (PDE):** Methylxanthines non-selectively inhibit PDE enzymes (primarily PDE3 and PDE4). This prevents the degradation of cyclic AMP (cAMP), leading to increased intracellular cAMP levels. In bronchial smooth muscle, this results in relaxation and bronchodilation. 2. **Antagonism of Adenosine:** Adenosine acts on A1 and A2 receptors to cause bronchoconstriction and histamine release from mast cells. Methylxanthines act as competitive antagonists at adenosine receptors, thereby preventing these effects. 3. **Intracellular Release of Ca²⁺:** At higher concentrations, methylxanthines promote the release of calcium from the sarcoplasmic reticulum in skeletal and cardiac muscles. This explains their positive inotropic effect on the heart and improved contractility of the diaphragm (useful in COPD). Since all three mechanisms are characteristic of methylxanthines, **Option D** is the correct answer. **High-Yield Clinical Pearls for NEET-PG:** * **Therapeutic Window:** Theophylline has a narrow therapeutic index (10–20 µg/ml). Monitoring is essential to avoid toxicity (seizures, arrhythmias). * **Metabolism:** It is metabolized by **CYP1A2**. Enzyme inducers (Rifampicin, Smoking) decrease its levels, while inhibitors (Ciprofloxacin, Erythromycin) increase levels, leading to toxicity. * **Additional Action:** They also enhance **Histone Deacetylation**, which helps reverse corticosteroid resistance in COPD and asthma patients.

Question 96: Which of the following is the primary bronchodilator used in the management of COPD?

A. Anticholinergics (Correct Answer)
B. Antiadrenergic agents
C. Cholinergic agents
D. Alpha agonists

Explanation: **Explanation:** In Chronic Obstructive Pulmonary Disease (COPD), the primary reversible component of airway obstruction is **vagal-mediated cholinergic tone**. Unlike asthma, where inflammation is the driver, COPD is characterized by increased parasympathetic activity leading to bronchoconstriction. **1. Why Anticholinergics are Correct:** Anticholinergics (Muscarinic antagonists) like **Ipratropium (SAMA)** and **Tiotropium (LAMA)** are considered the first-line bronchodilators in COPD. They work by blocking M3 receptors on bronchial smooth muscle, thereby inhibiting the bronchoconstrictor effect of acetylcholine. Tiotropium is particularly favored due to its long duration of action and selectivity for M3 receptors. **2. Why Incorrect Options are Wrong:** * **Antiadrenergic agents:** These (e.g., Beta-blockers) would cause bronchoconstriction and worsen COPD symptoms. * **Cholinergic agents:** These (e.g., Methacholine) stimulate muscarinic receptors, causing profound bronchoconstriction and mucus secretion, which is contraindicated in COPD. * **Alpha agonists:** These primarily cause vasoconstriction (alpha-1) or inhibit norepinephrine release (alpha-2). They have no significant role in bronchodilation; **Beta-2 agonists** (not alpha) are the adrenergic agents used for bronchodilation. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice (DOC):** For symptomatic relief in COPD, LAMAs (Tiotropium) are generally superior to LABAs. * **Combination Therapy:** In advanced COPD, a combination of LAMA + LABA is more effective than monotherapy. * **Side Effects:** The most common side effect of inhaled anticholinergics is **dry mouth**. Use with caution in patients with narrow-angle glaucoma or prostatic hyperplasia. * **Asthma vs. COPD:** While Beta-2 agonists are the mainstay for Asthma, Anticholinergics are the mainstay for COPD.

Question 97: Which of the following statements about theophylline is TRUE?

A. Its use in asthma has declined because of a narrow safety margin. (Correct Answer)
B. Its dose needs to be reduced in smokers.
C. It acts by increasing the formation of cAMP.
D. Its plasma half-life is longer in children compared to adults.

Explanation: **Theophylline** is a methylxanthine derivative that was once a mainstay in asthma management but is now considered a second or third-line agent. ### **Explanation of Options** * **Option A (Correct):** Theophylline has a **narrow therapeutic index (10–20 µg/mL)**. Toxicity can occur at levels only slightly above the therapeutic range, manifesting as severe arrhythmias, seizures, and persistent vomiting. Due to this narrow safety margin and the availability of safer alternatives like ICS and LABAs, its clinical use has significantly declined. * **Option B (Incorrect):** Smoking **induces hepatic enzymes (CYP1A2)**, which accelerates the metabolism of theophylline. Therefore, smokers actually require a **higher dose**, not a reduced one. * **Option C (Incorrect):** Theophylline acts by **inhibiting the enzyme Phosphodiesterase (PDE)**, primarily PDE3 and PDE4. This inhibition prevents the breakdown of cAMP, leading to **increased levels of cAMP**, rather than increasing its initial formation (which is the mechanism of beta-2 agonists). * **Option D (Incorrect):** Theophylline is metabolized faster in children. Consequently, its plasma half-life is **shorter in children** (approx. 3–5 hours) compared to non-smoking adults (approx. 7–9 hours). ### **High-Yield Clinical Pearls for NEET-PG** * **Mechanism of Action:** 1. PDE inhibition (increases cAMP); 2. Adenosine receptor antagonism (bronchodilation); 3. Histone deacetylase activation (anti-inflammatory effect). * **Drug Interactions:** * **Levels increased by:** Erythromycin, Ciprofloxacin, and Cimetidine (Enzyme inhibitors). * **Levels decreased by:** Phenytoin, Rifampicin, and Smoking (Enzyme inducers). * **Toxicity:** The earliest sign of toxicity is usually gastric irritation/vomiting; the most serious are cardiac arrhythmias and intractable seizures.

Question 98: All of the following are useful in the management of acute asthma except?

A. Hydrocortisone intravenously
B. Salbutamol inhalation
C. Salmeterol inhalation (Correct Answer)
D. Terbutaline inhalation

Explanation: ### Explanation The management of **acute asthma** (or status asthmaticus) requires drugs with a rapid onset of action to reverse bronchoconstriction and reduce inflammation immediately. **Why Salmeterol is the Correct Answer:** Salmeterol is a **Long-Acting Beta-2 Agonist (LABA)**. While it has high potency, it is highly lipophilic, leading to a **slow onset of action** (approximately 15–20 minutes). In an acute attack, immediate bronchodilation is critical; therefore, LABAs like Salmeterol are contraindicated for rescue therapy. They are strictly used for the long-term maintenance and prophylaxis of asthma. **Analysis of Incorrect Options:** * **Salbutamol & Terbutaline (Inhalation):** These are **Short-Acting Beta-2 Agonists (SABA)**. They are the "gold standard" and first-line treatment for acute exacerbations because they provide rapid bronchodilation within 1–5 minutes. * **Hydrocortisone (Intravenous):** Systemic corticosteroids are essential in acute severe asthma to reduce airway inflammation and edema. While they take 4–6 hours to show clinical effects, they are started immediately to prevent late-phase responses and improve the responsiveness of beta-receptors. **High-Yield NEET-PG Pearls:** * **Formoterol Exception:** Unlike Salmeterol, **Formoterol** is a LABA with a **fast onset of action**, making it suitable for both maintenance and reliever therapy (SMART therapy). * **Drug of Choice (DOC):** For acute asthma, the DOC is inhaled Salbutamol. For prophylaxis, the DOC is Inhaled Corticosteroids (ICS). * **Side Effects:** Tremors are the most common side effect of Beta-2 agonists due to the stimulation of $\beta_2$ receptors in skeletal muscles. Hypokalemia is also a known metabolic complication.

Question 99: What is the management for steroid-resistant asthma?

A. Oral steroids (Correct Answer)
B. Long-acting beta-2 agonist
C. Leukotriene antagonist
D. Theophylline

Explanation: **Explanation:** The management of **steroid-resistant asthma** (also known as corticosteroid-insensitive asthma) is a clinical challenge where patients do not respond to standard doses of inhaled corticosteroids (ICS). 1. **Why Oral Steroids are correct:** In clinical practice, "steroid resistance" is often relative rather than absolute. The first step in managing a patient who fails to respond to inhaled therapy is to escalate to **high-dose oral corticosteroids** (e.g., Prednisolone). This helps differentiate between poor inhaler technique/compliance and true molecular resistance. If the patient responds to oral doses, they are classified as "steroid-dependent" rather than truly resistant. 2. **Why other options are incorrect:** * **Long-acting beta-2 agonists (LABA):** These are "controllers" used as add-on therapy to ICS (Step 3 onwards) but do not address the underlying inflammatory resistance. * **Leukotriene antagonists (e.g., Montelukast):** These are useful as steroid-sparing agents or for aspirin-sensitive asthma, but they are not the primary management for steroid resistance. * **Theophylline:** This acts as a weak bronchodilator and phosphodiesterase inhibitor. While it may have some synergistic effects, it is not the first-line escalation for steroid resistance. **High-Yield Clinical Pearls for NEET-PG:** * **Molecular Mechanism:** Steroid resistance is often linked to reduced expression or activity of **Histone Deacetylase-2 (HDAC2)** and increased levels of the **Glucocorticoid Receptor-beta (GR-β)** isoform, which acts as a dominant-negative inhibitor. * **True Resistance:** If oral steroids also fail, the next steps include biologicals like **Omalizumab** (Anti-IgE), **Mepolizumab** (Anti-IL5), or immunosuppressants like **Methotrexate** and **Cyclosporine**. * **Smoking Link:** Smoking is a common cause of secondary steroid resistance due to oxidative stress inactivating HDAC2.

Question 100: Which of the following is a long-acting beta-2 agonist?

A. Salmeterol (Correct Answer)
B. Orciprenaline
C. Penoterol
D. Pexbaterol

Explanation: **Explanation:** **Beta-2 Agonists** are classified based on their duration of action into Short-Acting (SABA) and Long-Acting (LABA). **1. Why Salmeterol is Correct:** **Salmeterol** is a potent **Long-Acting Beta-2 Agonist (LABA)**. It possesses a long lipophilic side chain that anchors the molecule to the "exosite" near the beta-2 receptor, allowing the active head to repeatedly engage the receptor. This results in a prolonged duration of action (**>12 hours**). It is used for the maintenance treatment of asthma and COPD but is **not** suitable for acute attacks due to its slow onset of action. **2. Analysis of Incorrect Options:** * **Orciprenaline (Metaproterenol):** This is a non-selective beta-agonist with a short duration of action. It is rarely used now due to significant cardiac side effects (Beta-1 stimulation). * **Fenoterol (misspelled as Penoterol):** This is a **Short-Acting Beta-2 Agonist (SABA)**. It has a rapid onset and a short duration (4–6 hours), typically used for "rescue" therapy in acute bronchospasm. * **Terbutaline (misspelled as Pexbaterol):** Assuming the option refers to common SABAs like Terbutaline or Bambuterol; Terbutaline is a SABA. (Note: *Bambuterol* is a prodrug of terbutaline and is long-acting, but "Pexbaterol" is not a standard pharmacological agent). **3. High-Yield Clinical Pearls for NEET-PG:** * **LABAs:** Salmeterol and Formoterol (Duration: 12 hrs). **Indacaterol, Vilanterol, and Olodaterol** are "Ultra-LABAs" (Duration: 24 hrs). * **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** is unique because it is a LABA but also has a **fast onset of action**, making it useful in SMART (Single Maintenance and Reliever 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

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