Respiratory System Drugs Practice Questions

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

Phosphodiesterase 4 inhibition. **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.

Q: 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?

Lipoxygenase inhibitor. **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**.

Q: A 34-year-old man presents with increasing shortness of breath. He has a history of asthma that was previously well controlled, but two weeks ago he developed cold symptoms and has noticed increased coughing and shortness of breath since then. He reports no fevers or chills and denies sputum production. He is currently using his salbutamol inhaler six times a day for rescue therapy and feels unwell. His physical examination reveals wheezing on expiration, but is otherwise normal. A chest X-ray is normal. He is prescribed prednisone 30 mg once daily for one week. What is the primary mechanism of glucocorticoids in the management of asthma?

Anti-inflammatory effect. **Explanation:** **Why Option A is correct:** Asthma is fundamentally a **chronic inflammatory disorder** of the airways. Glucocorticoids (like Prednisone) are the most effective anti-inflammatory agents used in its management. Their primary mechanism involves: 1. **Inhibition of inflammatory mediators:** They inhibit the synthesis of cytokines (IL-4, IL-5), leukotrienes, and prostaglandins. 2. **Reduction of inflammatory cells:** They induce apoptosis of eosinophils and T-lymphocytes and decrease mast cell density. 3. **Up-regulation of Beta-2 receptors:** They increase the expression of $\beta_2$-adrenergic receptors on airway smooth muscle, which enhances the responsiveness to bronchodilators (synergistic effect). **Why the other options are incorrect:** * **B. Bronchodilatory effect:** Glucocorticoids do **not** have a direct relaxant effect on airway smooth muscle. Bronchodilation is achieved by $\beta_2$-agonists (e.g., Salbutamol) or anticholinergics (e.g., Ipratropium) [1]. * **C. Sedative effect:** Glucocorticoids do not cause sedation; in fact, they can cause CNS side effects like insomnia, euphoria, or psychosis. * **D. Mucolytic effect:** While steroids reduce mucus hypersecretion by decreasing inflammation, they do not chemically break down mucus (the role of mucolytics like N-acetylcysteine). **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice:** Inhaled Corticosteroids (ICS) are the first-line maintenance therapy for persistent asthma [1]. * **Systemic Steroids:** Reserved for acute exacerbations (as seen in this patient) to prevent relapse and speed up recovery [1]. * **Side Effects:** Long-term ICS use carries a risk of **oropharyngeal candidiasis** (prevented by using a spacer and rinsing the mouth) and dysphonia. * **Mechanism Tip:** Steroids act via **intracellular receptors** to alter gene transcription (genomic effect), which is why their clinical onset takes several hours. [1]

Q: Mucociliary clearance is increased in cystic fibrosis by which of the following agents?

Amiloride. ### Explanation **Correct Option: B (Amiloride)** **Mechanism and Concept:** In Cystic Fibrosis (CF), the defect in the CFTR protein leads to two major ionic imbalances in the airway epithelium: decreased chloride secretion and **increased sodium reabsorption** via the Epithelial Sodium Channel (ENaC) [1]. This excessive sodium uptake causes water to follow osmotically out of the airway lumen, leading to dehydrated, viscid mucus that impairs mucociliary clearance [1]. **Amiloride** is a potassium-sparing diuretic that acts as an **ENaC inhibitor**. When administered as an aerosol, it blocks the hyperactive sodium channels in the respiratory tract. By preventing excessive sodium (and subsequently water) reabsorption, it helps maintain airway surface liquid volume, thins the mucus, and thereby **increases mucociliary clearance**. **Analysis of Incorrect Options:** * **A. Mannitol:** While inhaled hypertonic saline and dry powder mannitol are used as osmotic agents to hydrate mucus, they do not directly inhibit the sodium channels responsible for the primary pathophysiology. In many standardized exams, Amiloride is the classic pharmacological answer for ENaC-mediated clearance improvement. * **C. Acetazolamide:** This is a carbonic anhydrase inhibitor used primarily for glaucoma, altitude sickness, and metabolic alkalosis [2]. It has no significant role in improving airway mucociliary clearance in CF. **High-Yield Clinical Pearls for NEET-PG:** * **CFTR Mutation:** Most common is **ΔF508** (Class II defect: protein misfolding and trafficking failure). * **Diagnosis:** Sweat chloride >60 mEq/L is the gold standard. * **Other Clearance Agents:** Recombinant human DNase (**Dornase alfa**) is used to digest extracellular DNA from neutrophils in CF sputum to reduce viscosity. * **Ivacaftor:** A CFTR "potentiator" used for specific gating mutations (Class III).

Q: A 34-year-old man with a long history of asthma is referred to a pulmonologist. The physician decides to prescribe zileuton. What is the mechanism of action of zileuton?

Inhibit 5-lipoxygenase. ### Explanation **Correct Option: B. Inhibit 5-lipoxygenase** Zileuton is a specific inhibitor of **5-lipoxygenase (5-LOX)**, the key enzyme responsible for converting arachidonic acid into leukotrienes (LTB4, LTC4, LTD4, and LTE4). By inhibiting this enzyme, zileuton prevents the synthesis of all leukotrienes. In asthma, leukotrienes are potent mediators that cause bronchoconstriction, increased mucus secretion, and airway edema. By blocking their production, zileuton helps in the prophylactic management of chronic asthma. **Analysis of Incorrect Options:** * **Option A (Antagonize LTD4 receptor):** This is the mechanism of **Montelukast** and **Zafirlukast**. These drugs block the CysLT1 receptor rather than inhibiting the synthesis of leukotrienes. * **Option C (Inhibit phosphodiesterases):** This is the mechanism of **Theophylline** (non-selective PDE inhibitor) and **Roflumilast** (PDE-4 inhibitor). These drugs increase cAMP levels to cause bronchodilation. * **Option D (Stimulate beta2 receptors):** This describes **Beta-agonists** like Salbutamol (SABA) or Salmeterol (LABA), which act via Gs-protein coupled receptors to relax bronchial smooth muscle. **High-Yield Clinical Pearls for NEET-PG:** * **Hepatotoxicity:** Zileuton is associated with an elevation in liver enzymes; therefore, periodic **LFT monitoring** is mandatory. * **Metabolism:** It is a microsomal enzyme inhibitor and can increase the plasma levels of **Theophylline** and **Warfarin**. * **Aspirin-Exacerbated Respiratory Disease (AERD):** Leukotriene modifiers (both 5-LOX inhibitors and receptor antagonists) are particularly effective in patients with "Aspirin Triad" (Asthma, Nasal polyps, and Aspirin sensitivity). * **Route:** Unlike many asthma drugs, Zileuton is administered **orally**.

Q: Relatively higher dose of theophylline is required to attain therapeutic plasma concentration in:

Smokers. **Explanation:** Theophylline is a methylxanthine with a narrow therapeutic index (10–20 µg/ml). It is primarily metabolized in the liver by the **Cytochrome P450 (CYP1A2)** enzyme system. **Why Smokers require a higher dose:** Cigarette smoking (and marijuana) introduces polycyclic aromatic hydrocarbons, which act as **potent enzyme inducers** of CYP1A2. This increases the metabolic clearance of theophylline, shortening its half-life. Consequently, smokers require a **higher dose** (often 50-100% more) to maintain therapeutic plasma concentrations compared to non-smokers. **Analysis of Incorrect Options:** * **Congestive Heart Failure (CHF):** CHF causes hepatic congestion and reduced blood flow to the liver, which **decreases** theophylline clearance. These patients require a *lower* dose to avoid toxicity. * **Erythromycin:** This is a known **enzyme inhibitor**. It inhibits the CYP system, leading to decreased metabolism and increased plasma levels of theophylline. A *lower* dose is required. * **Cimetidine:** Similar to erythromycin, cimetidine is a classic **enzyme inhibitor** that reduces theophylline clearance, necessitating a *lower* dose. **High-Yield Clinical Pearls for NEET-PG:** * **Enzyme Inducers (Need higher dose):** Smoking, Phenytoin, Rifampicin, Phenobarbitone, Carbamazepine. * **Enzyme Inhibitors (Need lower dose):** Cimetidine, Erythromycin (Macrolides), Ciprofloxacin (Fluoroquinolones), Allopurinol. * **Toxicity:** Early signs include anorexia, nausea, and vomiting. Severe toxicity leads to **cardiac arrhythmias** and **seizures**. * **Mechanism:** Non-selective phosphodiesterase (PDE) inhibition and adenosine receptor antagonism.

Q: A child was given a leukotriene receptor antagonist for prophylaxis of asthma. Which of the following drugs is a leukotriene receptor antagonist?

Montelukast. ### Explanation **Correct Option: A (Montelukast)** Leukotrienes (specifically $LTC_4$, $LTD_4$, and $LTE_4$) are potent bronchoconstrictors and mediators of inflammation in asthma. **Montelukast** and **Zafirlukast** are selective and competitive **CysLT₁ receptor antagonists**. By blocking these receptors on bronchial smooth muscle, they prevent bronchoconstriction, airway edema, and mucus secretion. They are primarily used for the **prophylaxis** of bronchial asthma and are particularly effective in **aspirin-induced asthma** and exercise-induced bronchospasm. **Analysis of Incorrect Options:** * **B. Zileuton:** While this drug affects the leukotriene pathway, it is a **5-Lipoxygenase (5-LOX) inhibitor**, not a receptor antagonist. It prevents the synthesis of leukotrienes from arachidonic acid. * **C. Nedocromil:** This is a **Mast Cell Stabilizer** (similar to Sodium Cromoglycate). It prevents the degranulation of mast cells and the release of inflammatory mediators like histamine but does not act directly on leukotriene receptors. * **D. Verapamil:** This is a **Phenylalkylamine Calcium Channel Blocker (CCB)** used primarily for hypertension, angina, and supraventricular arrhythmias. It has no therapeutic role in asthma management. **High-Yield NEET-PG Pearls:** * **Churg-Strauss Syndrome:** A rare but high-yield side effect associated with the use of leukotriene antagonists (Montelukast/Zafirlukast) is the unmasking of systemic vasculitis. * **Neuropsychiatric Events:** The FDA has issued a boxed warning for Montelukast regarding serious mental health side effects (e.g., agitation, aggression, suicidal ideation). * **Route:** Montelukast is administered **orally**, making it a preferred choice for pediatric patients who struggle with inhaler techniques.

Q: A 29-year-old woman presents with increasing shortness of breath and coughing. She had asthma as a child but has not required any treatment for the past 10 years. On examination, she has expiratory wheezes. For the above patient, select the most appropriate medication to cause bronchodilation.

albuterol. ### Explanation **Correct Option: A. Albuterol** The patient is presenting with an acute exacerbation of asthma, characterized by shortness of breath and expiratory wheezes. The primary goal in acute management is to reverse bronchoconstriction. **Albuterol** is a **Short-Acting Beta-2 Agonist (SABA)**. It works by stimulating $\beta_2$ receptors on bronchial smooth muscle, leading to an increase in intracellular cAMP, which results in rapid smooth muscle relaxation and bronchodilation. It is the "rescue" drug of choice for acute symptoms. **Analysis of Incorrect Options:** * **B. Ethanol:** Alcohol has no role in bronchodilation. In some patients, it may even trigger asthma symptoms due to histamine release or sulfite preservatives. * **C. Amitriptyline:** This is a Tricyclic Antidepressant (TCA). It possesses significant **anticholinergic** side effects (like dry mouth), but it is not used for respiratory therapy. Furthermore, TCAs can occasionally worsen respiratory depression in overdose. * **D. NSAIDs:** Non-Steroidal Anti-inflammatory Drugs (like Aspirin) are generally **contraindicated** or used with caution in asthmatics. They can shift arachidonic acid metabolism toward the leukotriene pathway, potentially triggering **Aspirin-Exacerbated Respiratory Disease (AERD)** or "Samter’s Triad." **Clinical Pearls for NEET-PG:** * **Drug of Choice (DOC):** SABAs (Albuterol/Salbutamol) are the DOC for acute asthma attacks. * **Mechanism:** $\beta_2$ agonists $\rightarrow$ $\uparrow$ Adenyl Cyclase $\rightarrow$ $\uparrow$ cAMP $\rightarrow$ Bronchodilation. * **Side Effects:** Tremors (most common, due to $\beta_2$ stimulation in skeletal muscle), tachycardia, and hypokalemia. * **Samter’s Triad:** Asthma, Aspirin sensitivity, and Nasal polyps. * **Maintenance:** Inhaled Corticosteroids (ICS) are the mainstay for long-term control (e.g., Fluticasone, Budesonide).

Q: All adverse effects of theophylline are mediated by adenosine A1 receptor antagonism, except:

Gastrointestinal discomfort. **Explanation:** Theophylline, a methylxanthine used in asthma and COPD, has a narrow therapeutic index and acts via two primary mechanisms: **non-selective phosphodiesterase (PDE) inhibition** (increasing cAMP) and **adenosine receptor antagonism**. **1. Why Gastrointestinal (GI) discomfort is the correct answer:** GI side effects, such as nausea, vomiting, and abdominal pain, are primarily mediated by **PDE inhibition** and direct local irritation of the gastric mucosa. Unlike the other options, these effects are not linked to adenosine receptor blockade. **2. Analysis of Incorrect Options (Adenosine-mediated effects):** Adenosine normally acts as an inhibitory neuromodulator in the body. By antagonizing adenosine receptors (specifically A1 and A2), theophylline causes: * **Cardiac Arrhythmias (A):** Adenosine normally slows the heart rate (negative chronotropy/dromotropy). Antagonism leads to tachycardia and arrhythmias. * **Diuresis (B):** Adenosine causes afferent arteriolar constriction in the kidney. Antagonizing this leads to vasodilation, increased renal blood flow, and diuresis. * **Seizures (C):** Adenosine is a potent CNS depressant. Antagonism at A1 receptors in the brain leads to CNS excitation, lowering the seizure threshold. **Clinical Pearls for NEET-PG:** * **Therapeutic Range:** 10–20 µg/mL. Toxicity often starts >20 µg/mL. * **Metabolism:** It follows **zero-order kinetics** in overdose. * **Drug Interactions:** Enzyme inhibitors (Cimetidine, Erythromycin, Ciprofloxacin) increase theophylline levels, while enzyme inducers (Rifampicin, Phenytoin, Smoking) decrease them. * **DOC for Toxicity:** Activated charcoal (multiple doses) or Hemoperfusion in severe cases.

Question 1

What is the mechanism of action of theophylline in bronchial asthma?

Accepted Answer

Phosphodiesterase 4 inhibition

Answer

Beta2 agonism

Answer

Anticholinergic action

Answer

Inhibition of mucociliary clearance

Question 2

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?

Accepted Answer

Lipoxygenase inhibitor

Answer

Chromone agent

Answer

Leukotriene receptor antagonist

Answer

Methylxanthines

Question 3

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?

Accepted Answer

Nervousness

Answer

Nasal congestion

Answer

Lethargy

Answer

Hyperkalemia

Question 4

A 34-year-old man presents with increasing shortness of breath. He has a history of asthma that was previously well controlled, but two weeks ago he developed cold symptoms and has noticed increased coughing and shortness of breath since then. He reports no fevers or chills and denies sputum production. He is currently using his salbutamol inhaler six times a day for rescue therapy and feels unwell. His physical examination reveals wheezing on expiration, but is otherwise normal. A chest X-ray is normal. He is prescribed prednisone 30 mg once daily for one week. What is the primary mechanism of glucocorticoids in the management of asthma?

Accepted Answer

Anti-inflammatory effect

Answer

Bronchodilatory effect

Answer

Sedative effect

Answer

Mucolytic effect

Question 5

Mucociliary clearance is increased in cystic fibrosis by which of the following agents?

Accepted Answer

Amiloride

Answer

Mannitol

Answer

Acetazolamide

Answer

None of the above

Question 6

A 34-year-old man with a long history of asthma is referred to a pulmonologist. The physician decides to prescribe zileuton. What is the mechanism of action of zileuton?

Accepted Answer

Inhibit 5-lipoxygenase

Answer

Antagonize leukotriene D4 receptor

Answer

Inhibit phosphodiesterases

Answer

Stimulate beta2 receptors

Question 7

Relatively higher dose of theophylline is required to attain therapeutic plasma concentration in:

Accepted Answer

Smokers

Answer

Congestive heart failure patients

Answer

Those receiving erythromycin

Answer

Those receiving cimetidine

Question 8

A child was given a leukotriene receptor antagonist for prophylaxis of asthma. Which of the following drugs is a leukotriene receptor antagonist?

Accepted Answer

Montelukast

Answer

Zileuton

Answer

Nedocromil

Answer

Verapamil

Question 9

A 29-year-old woman presents with increasing shortness of breath and coughing. She had asthma as a child but has not required any treatment for the past 10 years. On examination, she has expiratory wheezes. For the above patient, select the most appropriate medication to cause bronchodilation.

Accepted Answer

albuterol

Answer

ethanol

Answer

amitriptyline

Answer

NSAIDs

Question 10

All adverse effects of theophylline are mediated by adenosine A1 receptor antagonism, except:

Accepted Answer

Gastrointestinal discomfort

Answer

Cardiac arrhythmias

Answer

Diuresis

Answer

Seizures

Respiratory System Drugs — MCQs

Respiratory System Drugs — MCQs

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