Respiratory System Drugs Practice Questions

Q: A night shift worker complains of profuse rhinorrhea and sneezing for the past few days. Which among the following drugs can be given to him?

Fexofenadine. **Explanation:** The patient is a **night shift worker** presenting with symptoms of allergic rhinitis (rhinorrhea and sneezing). The primary clinical consideration here is the side effect profile of antihistamines, specifically **sedation and psychomotor impairment**. **1. Why Fexofenadine is correct:** Fexofenadine is a **Second-Generation Antihistamine (SGA)**. Unlike first-generation agents, SGAs are highly polar, have low lipid solubility, and are substrates for the P-glycoprotein efflux pump. This prevents them from crossing the blood-brain barrier (BBB) in significant amounts. Fexofenadine is specifically classified as a **"non-sedating"** antihistamine because it is devoid of CNS depressant effects even at higher doses. For a night shift worker, maintaining alertness is crucial for safety and performance. **2. Why the other options are incorrect:** * **Promethazine, Chlorpheniramine, and Pheniramine** are all **First-Generation Antihistamines**. These drugs are highly lipid-soluble and readily cross the BBB. They cause significant sedation, drowsiness, and impairment of concentration by blocking H1 receptors in the CNS. Using these in a shift worker could lead to occupational hazards or accidents. **High-Yield Clinical Pearls for NEET-PG:** * **Fexofenadine** is the active metabolite of Terfenadine. It lacks the cardiotoxic risk (QT prolongation/Torsades de pointes) associated with its parent drug. * **Cetirizine** is a second-generation agent but is known to cause "mild sedation" in some patients compared to Fexofenadine or Loratadine. * **Bilastine and Mizolastine** are other newer non-sedating antihistamines frequently tested. * **Azelastine** is a topical (nasal spray) H1 blocker often used for rapid relief in allergic rhinitis.

Q: A child suffering from asthma is to be treated with a drug that blocks the synthesis of leukotrienes. What drug would be an appropriate choice?

Zileuton. ### Explanation The correct answer is **Zileuton**. **Mechanism of Action:** Leukotrienes (LTB4, LTC4, LTD4, and LTE4) are potent inflammatory mediators derived from arachidonic acid via the **5-Lipoxygenase (5-LOX)** pathway. Zileuton is a specific inhibitor of the 5-LOX enzyme, thereby directly **blocking the synthesis** of all leukotrienes. This reduction in leukotriene production helps decrease bronchoconstriction, airway edema, and mucus secretion in asthmatic patients. **Analysis of Incorrect Options:** * **Montelukast (Option B):** While this is a leukotriene modifier, it does not block synthesis. Instead, it is a **Leukotriene Receptor Antagonist (LTRA)** that selectively blocks the **CysLT1 receptor**. It prevents leukotrienes from binding to their target but does not stop their production. * **Cromolyn sodium (Option A):** This is a **Mast Cell Stabilizer**. It prevents the degranulation of mast cells and the subsequent release of histamine and leukotrienes but does not inhibit the biochemical synthesis pathway of leukotrienes. * **Theophylline (Option D):** A methylxanthine that acts primarily as a **Phosphodiesterase (PDE) inhibitor** and adenosine receptor antagonist, leading to increased cAMP and bronchodilation. It has no direct effect on leukotriene synthesis. **High-Yield NEET-PG Pearls:** * **Zileuton Side Effect:** It is associated with **hepatotoxicity** (elevation of liver enzymes); therefore, periodic LFT monitoring is required. * **Aspirin-Exacerbated Respiratory Disease (AERD):** Leukotriene modifiers (Zileuton/Montelukast) are the drugs of choice for "Aspirin-induced asthma." * **Zafirlukast vs. Montelukast:** Zafirlukast inhibits CYP2C9 and CYP3A4, whereas Montelukast has fewer drug interactions and is more commonly used in children.

Q: Ivacaftor was approved by FDA for which condition?

Cystic fibrosis. **Explanation:** **Ivacaftor** is a breakthrough medication in the management of **Cystic Fibrosis (CF)**. It is classified as a **CFTR Potentiator**. Cystic fibrosis is caused by mutations in the *Cystic Fibrosis Transmembrane Conductance Regulator* (CFTR) gene, which leads to defective chloride ion transport across epithelial membranes. Ivacaftor works by increasing the "open-probability" time of the CFTR channel on the cell surface, thereby enhancing chloride transport and improving hydration of the airway surface liquid. It was initially approved for patients with the **G551D mutation** (the "gatekeeper" mutation). **Analysis of Incorrect Options:** * **B. Migraine:** Treatment typically involves triptans (5-HT1B/1D agonists), CGRP antagonists (Erenumab), or NSAIDs. Ivacaftor has no effect on neurovascular pathways. * **C. Hypertension:** Managed with diuretics, ACE inhibitors, ARBs, or Calcium Channel Blockers. Ivacaftor does not influence systemic vascular resistance or blood pressure. * **D. Glycogen storage disorders:** These are metabolic enzyme deficiencies (e.g., Von Gierke’s) managed primarily through dietary modifications and enzyme replacement, not ion channel modulation. **Clinical Pearls for NEET-PG:** * **Combination Therapy:** Ivacaftor is often combined with **Lumacaftor** or **Tezacaftor** (CFTR correctors) for the more common **F508del mutation**. * **Mechanism:** It addresses the *function* of the protein at the surface, whereas "correctors" address the *folding and trafficking* of the protein. * **Metabolism:** It is a substrate of **CYP3A4**; therefore, dosage adjustments are required when administered with CYP3A4 inhibitors (like ketoconazole) or inducers (like rifampin).

Q: 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?

Omalizumab. **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).

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

Codeine. **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.

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

Phenylephrine. **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.

Q: All of the following statements regarding theophylline are true EXCEPT:

Increased dose is required in cardiopulmonary disease. **Explanation:** Theophylline is a methylxanthine derivative used in the management of asthma and COPD. It has a **narrow therapeutic index** (10–20 µg/ml), meaning its dosage must be meticulously adjusted based on factors that influence its metabolism, primarily via the Cytochrome P450 (CYP1A2) system. **Why Option D is the Correct Answer (The False Statement):** In patients with **cardiopulmonary diseases** (such as Congestive Heart Failure or Cor Pulmonale) and **liver cirrhosis**, the hepatic metabolism of theophylline is significantly **decreased**. This leads to reduced clearance and an increased risk of toxicity. Therefore, a **decreased dose** (not increased) is required in these patients. **Analysis of Other Options:** * **Options A & B:** Theophylline acts by **inhibiting the enzyme Phosphodiesterase (PDE)**, specifically PDE3 and PDE4. This inhibition prevents the breakdown of cAMP, leading to **increased intracellular cAMP** levels, which results in bronchodilation and anti-inflammatory effects. It also acts as an Adenosine receptor antagonist. * **Option C:** Cigarette smoking induces the CYP1A2 enzyme. This accelerates the metabolism of theophylline, necessitating an **increased dose** to maintain therapeutic levels in smokers. **High-Yield Clinical Pearls for NEET-PG:** * **Drug Interactions:** Enzyme inhibitors like **Cimetidine, Erythromycin, and Ciprofloxacin** increase theophylline levels (risk of toxicity). Enzyme inducers like **Phenytoin and Rifampicin** decrease its levels. * **Toxicity Profile:** Early signs include GI upset and restlessness; severe toxicity leads to **cardiac arrhythmias** and **seizures** (refractory to anticonvulsants). * **Mechanism:** Apart from PDE inhibition, it also enhances **histone deacetylation**, which helps in reversing corticosteroid resistance in COPD.

Q: Reflex bronchoconstriction is most likely to occur with which of the following forms of inhaled antiasthma medication?

Dry powder inhaler (rotacap). **Explanation** The correct answer is **B. Dry powder inhaler (rotacap)**. **Why it is correct:** Dry powder inhalers (DPIs) require a **high inspiratory flow rate** to aerosolize the medication effectively. The inhalation of dry, fine particulate matter, combined with the high-velocity airflow required for delivery, can act as a mechanical and chemical irritant to the hyperreactive bronchial mucosa. This irritation frequently triggers **reflex bronchoconstriction** (cough or wheezing) immediately after inhalation. This is a classic side effect particularly noted in patients with severe asthma or highly sensitive airways. **Why other options are incorrect:** * **A. Metered Dose Inhaler (MDI):** These deliver medication in a fine mist (solution or suspension). While the propellant (CFCs/HFAs) can occasionally cause irritation, the particle impact is generally less irritating than dry powder. * **C. Nebulizer:** These deliver medication as a continuous, humidified mist over several minutes. Because the mist is moist and requires only tidal breathing, it is the least likely to cause mechanical irritation or reflex spasm. * **D. Nebulizer with a spacer:** This is a distractor; spacers are used with MDIs, not nebulizers. Spacers actually *reduce* the risk of irritation by slowing down particle velocity and reducing oropharyngeal deposition. **High-Yield Clinical Pearls for NEET-PG:** * **DPI Requirement:** Patients must be able to generate an inspiratory flow of **>30–60 L/min** for DPIs to be effective; hence, they are not suitable for children <5 years or patients in acute severe asthma. * **MDI + Spacer:** This combination is considered as effective as a nebulizer for treating acute exacerbations in most settings and reduces the "cold Freon effect" (reflex bronchospasm caused by cold propellant). * **Drug of Choice:** For immediate relief of bronchoconstriction, SABA (Salbutamol) remains the gold standard.

Question 1

A night shift worker complains of profuse rhinorrhea and sneezing for the past few days. Which among the following drugs can be given to him?

Accepted Answer

Fexofenadine

Answer

Promethazine

Answer

Chlorpheniramine

Answer

Pheniramine

Question 2

A child suffering from asthma is to be treated with a drug that blocks the synthesis of leukotrienes. What drug would be an appropriate choice?

Accepted Answer

Zileuton

Answer

Cromolyn sodium

Answer

Montelukast

Answer

Theophylline

Question 3

Ivacaftor was approved by FDA for which condition?

Accepted Answer

Cystic fibrosis

Answer

Migraine

Answer

Hypertension

Answer

Glycogen storage disorders

Question 4

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?

Accepted Answer

Omalizumab

Answer

Palivizumab

Answer

Natalizumab

Answer

Etilizumab

Question 5

Which opioid analgesic is used in the treatment of cough?

Accepted Answer

Codeine

Answer

Noscapine

Answer

Dextromethorphan

Answer

Meperidine

Question 6

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

Accepted Answer

None of the above

Answer

Beclomethasone

Answer

Budesonide

Answer

Ciclesonide

Question 7

Which oral and topical drug is used for nasal decongestion?

Accepted Answer

Phenylephrine

Answer

Histamine

Answer

Methoxamine

Answer

Dopamine

Question 8

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?

Accepted Answer

Corticosteroids increase bronchial responsiveness to bronchodilators like salbutamol.

Answer

Corticosteroids provide direct bronchodilation, particularly when used in conjunction with xanthines.

Answer

Corticosteroids indirectly enhance the effects of xanthines by acting on adenosine receptors.

Answer

Corticosteroids improve mucociliary clearance, contributing to symptom relief.

Question 9

All of the following statements regarding theophylline are true EXCEPT:

Accepted Answer

Increased dose is required in cardiopulmonary disease

Answer

Increases cAMP

Answer

Inhibits phosphodiesterase

Answer

Increased dose is required in smokers

Question 10

Reflex bronchoconstriction is most likely to occur with which of the following forms of inhaled antiasthma medication?

Accepted Answer

Dry powder inhaler (rotacap)

Answer

Metered dose inhaler spray of drug in solution

Answer

Nebulizer

Answer

Nebulizer with a spacer

Respiratory System Drugs — MCQs

Respiratory System Drugs — MCQs

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