Respiratory System Drugs — MCQs

Respiratory System Drugs Indian Medical PG Practice Questions and MCQs

Question 111: Vilanterol is FDA approved for the treatment of which condition?

A. Asthma
B. COPD (Correct Answer)
C. Both Asthma and COPD
D. None of the above

Explanation: **Explanation:** **Vilanterol** is an ultra-long-acting beta-2 agonist (uLABA) characterized by a rapid onset of action and a prolonged duration of effect (24 hours). 1. **Why COPD is correct:** Vilanterol is FDA-approved specifically for the maintenance treatment of airflow obstruction in patients with **Chronic Obstructive Pulmonary Disease (COPD)**, including chronic bronchitis and emphysema. It is typically used in fixed-dose combinations with long-acting muscarinic antagonists (LAMA) like Umeclidinium or inhaled corticosteroids (ICS) like Fluticasone furoate. 2. **Why Asthma is incorrect:** While Vilanterol is used in combination with Fluticasone furoate (Breo Ellipta) for asthma maintenance, **Vilanterol is NOT FDA-approved as a monotherapy for asthma.** In fact, the FDA maintains a "Black Box Warning" against using LABAs/uLABAs alone in asthma due to the increased risk of asthma-related death. In contrast, LABA monotherapy is acceptable and common in COPD management. 3. **Why "Both" is incorrect:** Because the question asks about the drug itself (Vilanterol), and its primary standalone indication and safety profile are rooted in COPD management, "COPD" is the most accurate answer for NEET-PG purposes. **High-Yield Clinical Pearls for NEET-PG:** * **Duration:** Vilanterol has a half-life that allows for **once-daily** dosing. * **Combinations:** * Vilanterol + Fluticasone furoate (ICS/LABA) * Vilanterol + Umeclidinium (LABA/LAMA) * Vilanterol + Umeclidinium + Fluticasone (Triple therapy - Trelegy Ellipta) * **Mechanism:** It works by increasing cyclic AMP, leading to relaxation of bronchial smooth muscle. * **Comparison:** Unlike Salmeterol (slow onset), Vilanterol has a **rapid onset** similar to Formoterol but lasts significantly longer.

Question 112: Which NMDA blocker is used as an antitussive?

A. Pholcodeine
B. Dextromethorphan (Correct Answer)
C. Diphenhydramine
D. Aprepitant

Explanation: **Explanation:** **Dextromethorphan (Option B)** is the correct answer. It is the d-isomer of the codeine analog levorphanol. Unlike its l-isomer counterpart, it does not have significant analgesic or addictive properties [1]. Its primary mechanism as an antitussive involves increasing the cough threshold in the medulla. Crucially for this question, it acts as a **non-competitive NMDA receptor antagonist** [2], which contributes to its efficacy and also explains its potential for dissociative effects (hallucinations) when taken in high doses (abuse potential) [3]. **Analysis of Incorrect Options:** * **Pholcodeine (Option A):** This is a semi-synthetic opioid antitussive [2]. While it is more potent than codeine and has a longer duration of action, its primary mechanism is via opioid receptors in the cough center, not NMDA blockade. * **Diphenhydramine (Option B):** This is a first-generation H1-receptor antagonist. It is used as an adjuvant in cough syrups primarily for its sedative and anticholinergic (drying) properties [3], rather than a direct NMDA-mediated antitussive effect. * **Aprepitant (Option D):** This is a Neurokinin-1 (NK1) receptor antagonist used primarily as an antiemetic in chemotherapy-induced nausea and vomiting (CINV). It has no established role as a standard antitussive. **High-Yield Clinical Pearls for NEET-PG:** * **Safety Profile:** Unlike codeine, Dextromethorphan does not cause constipation or significant respiratory depression at therapeutic doses and has no ciliary inhibition [1]. * **Drug Interaction:** It can cause **Serotonin Syndrome** if co-administered with MAO inhibitors or SSRIs, as it inhibits serotonin reuptake. * **Metabolism:** It is metabolized by the enzyme **CYP2D6**. * **Clinical Note:** It is the most commonly used over-the-counter (OTC) cough suppressant worldwide [1].

Question 113: Which monoclonal antibody targets IL-5?

A. Mepolizumab (Correct Answer)
B. Omalizumab
C. Keliximab
D. Altrakincept

Explanation: **Explanation:** **Mepolizumab** is a humanized monoclonal antibody that directly binds to and inhibits **Interleukin-5 (IL-5)** [1]. IL-5 is the primary cytokine responsible for the growth, differentiation, recruitment, and survival of eosinophils [1]. By neutralizing IL-5, Mepolizumab reduces eosinophilic inflammation, making it an effective "add-on" therapy for patients with severe eosinophilic asthma [1]. **Analysis of Incorrect Options:** * **Omalizumab:** This is a recombinant DNA-derived humanized IgG1 monoclonal antibody that binds selectively to **free IgE** in the blood and interstitial fluid [2]. It prevents IgE from binding to the high-affinity receptors (FcεRI) on mast cells and basophils, used primarily in severe allergic asthma [2]. * **Keliximab:** This is a monoclonal antibody that targets the **CD4 receptor** on T-lymphocytes. It was historically investigated for chronic asthma but is not a first-line treatment or a common IL-5 inhibitor. * **Altrakincept:** This is a recombinant soluble **IL-4 receptor** (not a monoclonal antibody). It acts as a decoy receptor to neutralize IL-4, thereby inhibiting the Th2 response. **High-Yield Clinical Pearls for NEET-PG:** * **IL-5 Antagonists:** Remember the "Mep-Res-Ben" trio: **Mepolizumab** and **Reslizumab** target the IL-5 ligand itself, while **Benralizumab** targets the IL-5 receptor (IL-5Rα). * **Indication:** These drugs are specifically used for **Severe Eosinophilic Asthma** (refractory to inhaled corticosteroids) [1]. * **Dupilumab:** Another high-yield drug that targets the **IL-4 receptor alpha subunit**, effectively blocking both IL-4 and IL-13 signaling.

Question 114: What is the mechanism of action of theophylline in bronchial asthma?

A. Phosphodiesterase 4 inhibition (Correct Answer)
B. Beta2 agonism
C. Anticholinergic action
D. Inhibition of mucociliary clearance

Explanation: **Explanation:** **Mechanism of Action (Theophylline):** Theophylline is a methylxanthine derivative that primarily acts by **inhibiting the enzyme Phosphodiesterase (PDE)**, specifically the **PDE4** isoenzyme. * **The Concept:** PDE normally breaks down cyclic Adenosine Monophosphate (cAMP). By inhibiting PDE, theophylline increases intracellular cAMP levels in bronchial smooth muscle and inflammatory cells. Elevated cAMP leads to smooth muscle relaxation (bronchodilation) and suppresses the release of inflammatory mediators from mast cells and basophils. * **Additional Mechanism:** It also acts as an **Adenosine receptor antagonist** (A1 and A2 receptors), preventing adenosine-induced bronchoconstriction. **Analysis of Incorrect Options:** * **B. Beta2 agonism:** This is the mechanism for drugs like Salbutamol and Salmeterol, which stimulate adenylyl cyclase to increase cAMP directly. * **C. Anticholinergic action:** This describes Ipratropium and Tiotropium, which block M3 muscarinic receptors to prevent vagally-mediated bronchoconstriction. * **D. Inhibition of mucociliary clearance:** Theophylline actually **increases** mucociliary clearance, which helps in clearing secretions; inhibiting it would be detrimental in asthma. **High-Yield Clinical Pearls for NEET-PG:** 1. **Narrow Therapeutic Index:** Theophylline requires Therapeutic Drug Monitoring (TDM). The target range is **5–15 µg/ml**. 2. **Toxicity:** Toxicity presents as persistent vomiting, cardiac arrhythmias, and seizures. 3. **Histone Deacetylation:** In low doses, theophylline activates histone deacetylase (HDAC2), which enhances the anti-inflammatory effects of corticosteroids—a key synergy in COPD. 4. **Drug Interactions:** Enzyme inhibitors (Cimetidine, Erythromycin, Ciprofloxacin) increase theophylline levels, while enzyme inducers (Rifampicin, Phenytoin, Smoking) decrease them.

Question 115: Which beta 2 agonist is not indicated for acute bronchial asthma?

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

Explanation: **Explanation:** The management of bronchial asthma categorizes $\beta_2$ agonists based on their onset and duration of action. The correct answer is **Salmeterol** because it is a **Long-Acting Beta-2 Agonist (LABA)**. **1. Why Salmeterol is the correct answer:** Salmeterol has a **slow onset of action** (approximately 15–20 minutes) and a long duration of action (12 hours). Because it does not provide immediate bronchodilation, it is contraindicated for the relief of acute bronchospasm or "rescue" therapy. Using it during an acute attack can lead to a delay in effective treatment. It is strictly indicated for maintenance therapy (prophylaxis) and is typically used in combination with inhaled corticosteroids (ICS). **2. Analysis of incorrect options:** * **Salbutamol (Albuterol) & Terbutaline:** These are **Short-Acting Beta-2 Agonists (SABA)**. They have a rapid onset of action (within 1–5 minutes) and are the "drugs of choice" for relieving acute asthma symptoms and exercise-induced bronchospasm. * **Methylxanthines (e.g., Theophylline):** While not first-line, intravenous Aminophylline (a methylxanthine derivative) has historically been used in refractory cases of acute severe asthma (status asthmaticus), though its use is declining due to toxicity. However, in the context of $\beta_2$ agonists, Salmeterol is the definitive "wrong" choice for acute relief. **3. NEET-PG High-Yield Pearls:** * **Formoterol Paradox:** Unlike Salmeterol, **Formoterol** is a LABA with a **fast onset of action**, making it the only LABA currently recommended for both maintenance and reliever therapy (SMART therapy) when combined with Budesonide. * **Chemical Structure:** Salmeterol is highly lipophilic, allowing it to remain in the lipid bilayer of the neuronal membrane, which accounts for its long duration. * **Side Effects:** Tachycardia, tremors, and hypokalemia are common side effects of $\beta_2$ agonists due to stimulation of $\beta_1$ (cross-reactivity) and $\beta_2$ receptors in skeletal muscle and the liver.

Question 116: In theophylline metabolism, drug interactions occur with all of the following except:

A. Cimetidine
B. Phenobarbitone
C. Rifampicin
D. Tetracyclines (Correct Answer)

Explanation: **Explanation:** Theophylline has a **narrow therapeutic index** (10-20 µg/ml) and is primarily metabolized by the hepatic **Cytochrome P450 (CYP1A2 and CYP3A4)** enzyme system. Consequently, its serum levels are highly sensitive to drugs that induce or inhibit these enzymes. **1. Why Tetracyclines is the correct answer:** Tetracyclines (like Doxycycline or Oxytetracycline) do not significantly inhibit or induce hepatic microsomal enzymes. Therefore, they do not alter the metabolism of theophylline. While some Macrolides (like Erythromycin) and Fluoroquinolones (like Ciprofloxacin) are notorious for increasing theophylline levels, **Tetracyclines are considered safe** in this regard. **2. Analysis of Incorrect Options:** * **Cimetidine:** A potent **enzyme inhibitor**. It inhibits CYP1A2 and CYP3A4, leading to decreased clearance of theophylline, which can result in theophylline toxicity (nausea, palpitations, seizures). * **Phenobarbitone:** A classic **enzyme inducer**. It increases the synthesis of microsomal enzymes, accelerating theophylline metabolism and potentially leading to sub-therapeutic levels and poor asthma control. * **Rifampicin:** A powerful **broad-spectrum enzyme inducer**. Similar to Phenobarbitone, it enhances the clearance of theophylline, necessitating a dosage increase. **High-Yield Clinical Pearls for NEET-PG:** * **Theophylline Toxicity:** Manifests as persistent vomiting, cardiac arrhythmias, and intractable seizures. * **Other Inhibitors (Increase levels):** Erythromycin, Ciprofloxacin, Oral Contraceptives, and Allopurinol. * **Other Inducers (Decrease levels):** Phenytoin, Carbamazepine, and **Smoking** (Polycyclic hydrocarbons induce CYP1A2). * **Mechanism:** Theophylline works by inhibiting Phosphodiesterase (PDE) and antagonizing Adenosine receptors.

Question 117: A 21-year-old woman with moderately severe asthma on three-drug treatment has elevated liver function tests thought to be caused by one of her medications. Which drug is causing this adverse effect?

A. Chromone agent
B. Lipoxygenase inhibitor (Correct Answer)
C. Leukotriene receptor antagonist
D. Methylxanthines

Explanation: **Explanation:** The correct answer is **Lipoxygenase inhibitor (Zileuton)**. **1. Why it is correct:** Zileuton is a selective inhibitor of 5-lipoxygenase (5-LOX), the enzyme responsible for converting arachidonic acid into leukotrienes. A well-documented and high-yield adverse effect of Zileuton is **hepatotoxicity**. It can cause a significant elevation in serum hepatic transaminases (ALT/AST), typically occurring within the first 2-3 months of therapy. Therefore, periodic liver function monitoring is mandatory for patients on this drug. **2. Why other options are incorrect:** * **Chromone agents (Cromolyn/Nedocromil):** These are mast cell stabilizers with an excellent safety profile. Their side effects are usually limited to local irritation (throat irritation or cough) and are not associated with liver injury. * **Leukotriene receptor antagonists (Montelukast/Zafirlukast):** While Zafirlukast has rare reports of hepatotoxicity, it is significantly less common than with Zileuton. Montelukast is generally considered safe for the liver. In the context of "three-drug treatment" and elevated LFTs, Zileuton is the classic pharmacological culprit. * **Methylxanthines (Theophylline):** These have a narrow therapeutic index, but toxicity typically manifests as GI upset, cardiac arrhythmias, or seizures, rather than primary hepatotoxicity. **Clinical Pearls for NEET-PG:** * **Zileuton:** Inhibits 5-LOX; causes hepatotoxicity; metabolized by CYP1A2 (increases levels of Theophylline and Warfarin). * **Montelukast/Zafirlukast:** Block CysLT1 receptors; used for aspirin-induced asthma and prophylaxis. * **Rule of Thumb:** If a question mentions asthma medications and liver enzymes, think **Zileuton**.

Question 118: Dr. Jones prescribes albuterol sulfate (Proventil) for a patient with newly diagnosed asthma. When teaching the patient about this drug, what adverse effect should the nurse explain is possible?

A. Nasal congestion
B. Nervousness (Correct Answer)
C. Lethargy
D. Hyperkalemia

Explanation: ### Explanation **Correct Option: B. Nervousness** Albuterol is a **short-acting beta-2 (β2) agonist (SABA)**. While it is designed to be selective for β2 receptors in the bronchial smooth muscle (causing bronchodilation), selectivity is not absolute, especially at higher doses. * **Mechanism:** Albuterol can cause CNS stimulation and cross-reactivity with **β1 receptors** (found in the heart) and peripheral **β2 receptors** (found in skeletal muscles). * **Clinical Manifestation:** Stimulation of these receptors leads to sympathetic overactivity, resulting in **nervousness, tremors (due to skeletal muscle β2 stimulation), and tachycardia**. Nervousness and tremors are the most common dose-limiting side effects reported by patients. **Analysis of Incorrect Options:** * **A. Nasal congestion:** This is incorrect. β-agonists typically cause vasoconstriction (if α-activity is present) or have no significant effect on nasal mucosa. Nasal congestion is more commonly associated with α-blockers or "rebound" effects from topical decongestants. * **C. Lethargy:** Albuterol is a stimulant, not a depressant. It causes CNS excitation (anxiety/insomnia) rather than sedation or lethargy. * **D. Hyperkalemia:** This is the opposite of the actual effect. β2 agonists stimulate the **Na+/K+-ATPase pump**, shifting potassium from the extracellular fluid into the cells. This leads to **hypokalemia**. (Note: This effect is utilized clinically to treat emergency hyperkalemia). **High-Yield NEET-PG Pearls:** 1. **Drug of Choice:** SABA (Albuterol/Salbutamol) is the DOC for **acute asthma exacerbations** (rescue inhaler). 2. **Metabolic Effects:** β2 agonists cause **hypokalemia, hyperglycemia, and hypomagnesemia**. 3. **Muscle Tremors:** This is the most common side effect of systemic/high-dose β2 agonists, mediated by β2 receptors in the skeletal muscles. 4. **Tolerance:** Overuse of SABAs can lead to **downregulation (tachyphylaxis)** of β receptors.

Question 119: Which monoclonal antibody is used in the management of asthma?

A. Omalizumab (Correct Answer)
B. Trastuzumab
C. Muromonab
D. Alemtuzumab

Explanation: **Omalizumab** is the correct answer because it is a recombinant DNA-derived humanized monoclonal antibody specifically designed for the management of moderate-to-severe persistent allergic asthma. [1] **Mechanism of Action:** Omalizumab binds selectively to **free circulating IgE**, forming complexes that prevent IgE from binding to its high-affinity receptors (FcεRI) on the surface of mast cells and basophils. This inhibits the release of inflammatory mediators (like histamine and leukotrienes) that trigger an asthma attack. It is typically indicated for patients whose symptoms are inadequately controlled by inhaled corticosteroids. [1] **Analysis of Incorrect Options:** * **Trastuzumab:** A monoclonal antibody against the **HER2/neu receptor**, used primarily in the treatment of HER2-positive breast cancer and gastric cancer. * **Muromonab (OKT3):** An anti-CD3 antibody used as an **immunosuppressant** to prevent acute rejection in organ transplantation. * **Alemtuzumab:** An anti-CD52 antibody used in the treatment of **Chronic Lymphocytic Leukemia (CLL)** and Multiple Sclerosis. **High-Yield Clinical Pearls for NEET-PG:** 1. **Route:** Administered via **subcutaneous injection** every 2–4 weeks. 2. **Other Biologicals in Asthma:** * **Anti-IL5:** Mepolizumab, Reslizumab (used for eosinophilic asthma). * **Anti-IL5 Receptor:** Benralizumab. * **Anti-IL4/IL13:** Dupilumab. 3. **Side Effect:** The most serious, though rare, side effect of Omalizumab is **anaphylaxis**; patients should be monitored post-injection.

Question 120: Which corticosteroid is administered via inhalation route?

A. Prednisolone
B. Beclomethasone (Correct Answer)
C. Dexamethasone
D. Hydrocortisone

Explanation: **Explanation:** The primary goal of corticosteroid therapy in respiratory conditions like bronchial asthma and COPD is to reduce airway inflammation while minimizing systemic side effects [1]. This is achieved through **Inhaled Corticosteroids (ICS)** [1]. **Why Beclomethasone is Correct:** **Beclomethasone dipropionate** is a potent, lipid-soluble corticosteroid specifically designed for inhalation. It acts locally on the bronchial mucosa to decrease inflammatory mediators and hyper-responsiveness [2]. Because it undergoes significant first-pass metabolism in the liver, any swallowed portion has minimal systemic bioavailability, reducing the risk of systemic toxicity (e.g., adrenal suppression) [2]. **Why Other Options are Incorrect:** * **Prednisolone:** A standard **oral** corticosteroid used for maintenance in severe chronic asthma or short "burst" therapy during acute exacerbations [1]. * **Dexamethasone:** A high-potency, long-acting corticosteroid typically administered **parenterally (IV/IM)** or orally. It is used in emergencies like status asthmaticus or for its anti-emetic and anti-inflammatory effects in systemic diseases. * **Hydrocortisone:** A short-acting corticosteroid used **intravenously** in acute severe asthma (status asthmaticus) for rapid systemic effect. **High-Yield Clinical Pearls for NEET-PG:** * **Other ICS Examples:** Budesonide (most common), Fluticasone, Ciclesonide, and Mometasone [2]. * **Ciclesonide:** It is a **prodrug** activated by esterases in the bronchial epithelium, further reducing local side effects like oropharyngeal candidiasis [2]. * **Side Effects of ICS:** The most common local side effects are **hoarseness of voice (dysphonia)** and **oropharyngeal candidiasis (thrush)**. Patients are advised to rinse their mouth with water after each use to prevent these [2]. * **Mechanism:** ICS do not cause immediate bronchodilation; they are "preventers" used for long-term control, not "relievers" for acute attacks [3].

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

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Oxygen Therapy

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