Respiratory System Drugs — MCQs

Respiratory System Drugs Indian Medical PG Practice Questions and MCQs

Question 211: Which of the following drugs is NOT useful during an acute attack of bronchial asthma?

A. Salbutamol
B. Hydrocortisone
C. Cromolyn sodium (Correct Answer)
D. Theophylline

Explanation: **Explanation:** The management of bronchial asthma is divided into **relievers** (for acute attacks) and **controllers** (for long-term prophylaxis). **Why Cromolyn Sodium is the correct answer:** Cromolyn sodium is a **Mast Cell Stabilizer**. It works by preventing the degranulation of mast cells and the subsequent release of inflammatory mediators (like histamine and leukotrienes). However, it has **no direct bronchodilatory action** and cannot reverse existing bronchoconstriction [2]. Therefore, it is strictly used for **prophylaxis** (e.g., exercise-induced or antigen-induced asthma) and is ineffective once an acute attack has started [2]. **Analysis of incorrect options:** * **Salbutamol:** A Short-Acting Beta-2 Agonist (SABA). It is the **drug of choice** for acute asthma because it causes rapid bronchodilation by increasing cAMP in airway smooth muscle [4]. Their primary effect is to dilate the bronchi by a direct action on the beta-2 adrenoceptors of smooth muscle [2]. * **Hydrocortisone:** An intravenous corticosteroid used in **Status Asthmaticus** (severe acute asthma) [1]. While it takes 4–6 hours to act, it is vital for reducing airway inflammation and upregulating beta-receptors to enhance the effect of bronchodilators [1]. * **Theophylline:** A methylxanthine that acts as a phosphodiesterase (PDE) inhibitor. Though less commonly used now due to its narrow therapeutic index, it can be used as an adjunctive bronchodilator in acute settings [2]. **NEET-PG High-Yield Pearls:** * **Drug of choice for acute asthma:** Inhaled Salbutamol (SABA) [4]. * **Drug of choice for prophylaxis (all steps):** Inhaled Corticosteroids (ICS) like Fluticasone [3]. * **Cromolyn Sodium side effect:** Throat irritation and "bronchospasm" (paradoxical), which can be prevented by pre-administering a SABA. * **Mechanism of Cromolyn:** Inhibits "Cl- channels" in mast cells, preventing calcium influx and degranulation.

Question 212: What is the primary use of leukotriene antagonists in asthma management?

A. To be used in conjunction with beta-agonists to reduce the need for steroids.
B. As a sole therapy in place of beta-blockers.
C. For prophylactic therapy in mild to moderate asthma. (Correct Answer)
D. As definitive therapy during an acute asthma attack.

Explanation: Leukotriene receptor antagonists (LTRAs) like **Montelukast** and **Zafirlukast** work by blocking the CysLT1 receptor, preventing bronchoconstriction, airway edema, and mucus secretion induced by cysteinyl leukotrienes. ### Why Option C is Correct LTRAs are primarily used for **prophylaxis** and long-term maintenance of mild to moderate persistent asthma. They are particularly effective in specific phenotypes, such as **aspirin-induced asthma** (where leukotriene production is shunted) and **exercise-induced bronchoconstriction**. Because they are administered orally, they also improve compliance in pediatric patients. ### Why Other Options are Incorrect * **Option A:** While LTRAs can be "steroid-sparing," they are typically used as add-on therapy to Inhaled Corticosteroids (ICS), not as a replacement for them in conjunction with beta-agonists. ICS remain the first-line controller therapy. * **Option B:** Beta-blockers are generally contraindicated in asthma; LTRAs do not replace them. If the option meant "beta-agonists," LTRAs cannot replace them for acute symptom relief. * **Option C:** LTRAs have a slow onset of action and are **not effective** for reversing acute bronchospasm. Short-acting beta-agonists (SABA) like Salbutamol remain the drug of choice for acute attacks. ### High-Yield NEET-PG Pearls * **Mechanism:** Montelukast/Zafirlukast are CysLT1 antagonists; **Zileuton** is a 5-Lipoxygenase (5-LOX) inhibitor. * **Aspirin Triad (Samter’s Triad):** Asthma, Nasal polyps, and Aspirin sensitivity. LTRAs are the preferred treatment here. * **Side Effects:** Generally well-tolerated, but watch for **Churg-Strauss syndrome** (eosinophilic granulomatosis with polyangiitis) and neuropsychiatric effects (mood changes/suicidal ideation). * **Metabolism:** Zafirlukast inhibits CYP3A4 and CYP2C9, potentially increasing Warfarin levels.

Question 213: Methyl xanthines act on which type of receptors?

A. Histamine receptors
B. Adenosine receptors (Correct Answer)
C. Mast cells
D. Cholinergic receptors

Explanation: **Explanation:** Methylxanthines (such as **Theophylline** and **Aminophylline**) primarily act through two major mechanisms of action: 1. **Adenosine Receptor Antagonism:** Adenosine normally causes bronchoconstriction and inhibits mediator release from mast cells by binding to $A_1$ and $A_2$ receptors. Methylxanthines act as competitive antagonists at these receptors, leading to bronchodilation. This is considered the most significant mechanism at therapeutic concentrations. 2. **Phosphodiesterase (PDE) Inhibition:** They inhibit PDE (mainly PDE3 and PDE4), preventing the breakdown of cAMP and cGMP. Increased intracellular cAMP levels lead to smooth muscle relaxation. **Analysis of Incorrect Options:** * **Option A (Histamine receptors):** Methylxanthines do not block histamine receptors ($H_1$ or $H_2$). While they may indirectly reduce histamine release, they are not antihistamines. * **Option C (Mast cells):** While methylxanthines do stabilize mast cell membranes (preventing degranulation), "Mast cells" are a cell type, not a receptor type. The question specifically asks for the receptor target. * **Option D (Cholinergic receptors):** Anticholinergics (like Ipratropium bromide) act here. Methylxanthines do not have significant direct action on muscarinic or nicotinic receptors. **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 like smoking and rifampicin decrease its levels, while inhibitors like ciprofloxacin and erythromycin increase toxicity risk. * **Other Effects:** They also cause CNS stimulation, diuresis, and increased gastric acid secretion.

Question 214: Which of the following is a short-acting beta-2 agonist?

A. Formoterol
B. Isoprenaline
C. Salbutamol (Correct Answer)
D. Salmeterol

Explanation: **Explanation:** **Salbutamol (Albuterol)** is the correct answer because it is a classic **Short-Acting Beta-2 Agonist (SABA)**. These drugs act rapidly (onset within 5 minutes) by stimulating $\beta_2$ receptors in the bronchial smooth muscle, leading to increased cAMP levels and subsequent bronchodilation. They are the "rescue medications" of choice for acute asthma exacerbations. **Analysis of Incorrect Options:** * **Formoterol (Option A):** This is a **Long-Acting Beta-2 Agonist (LABA)**. While it has a fast onset of action similar to Salbutamol, its duration of action is long (12 hours), classifying it as a LABA. * **Isoprenaline (Option B):** This is a **non-selective beta agonist** ($\beta_1$ and $\beta_2$). While it causes bronchodilation, it is not used for asthma due to significant cardiac side effects (tachycardia, arrhythmias) caused by $\beta_1$ stimulation. * **Salmeterol (Option D):** This is a prototypical **LABA**. It has a slow onset of action and a long duration (12+ hours), making it suitable for maintenance therapy but contraindicated for acute relief. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice:** SABAs (Salbutamol, Terbutaline, Levosalbutamol) are the DOC for **acute asthma attacks** and **exercise-induced bronchospasm**. * **Side Effects:** Muscle tremors (most common), tachycardia (due to $\beta_1$ cross-reactivity), and **hypokalemia** (used therapeutically to treat hyperkalemia). * **Mechanism:** They act via Gs-protein coupled receptors to activate adenylyl cyclase. * **SMART Therapy:** Formoterol is unique among LABAs because its rapid onset allows it to be used in Single Maintenance and Reliever Therapy (SMART).

Question 215: Which of the following mucolytics contains a free sulfhydryl group?

A. Guanfacine
B. Ambroxol
C. Carbocisteine
D. N-Acetylcysteine (Correct Answer)

Explanation: **Explanation:** **N-Acetylcysteine (NAC)** is the correct answer because its chemical structure contains a **free sulfhydryl (-SH) group**. This group is central to its mechanism of action as a mucolytic: it directly reduces (breaks) the **disulfide bonds** in the mucoprotein matrix of sputum. By breaking these cross-links, NAC reduces the viscosity and elasticity of thick mucus, making it easier to expectorate. **Analysis of Incorrect Options:** * **Guanfacine (A):** This is a centrally acting alpha-2 adrenergic agonist used primarily in the treatment of ADHD and hypertension; it has no mucolytic properties. * **Amboxol (B):** A metabolite of Bromhexine, it acts as a **mucokinetic** and **mucosecretolytic**. It works by stimulating the production of surfactant and thinning secretions, but it does not possess a free sulfhydryl group to break disulfide bonds directly. * **Carbocisteine (C):** While derived from cysteine, the sulfhydryl group in Carbocisteine is **blocked (alkylated)**. Therefore, it does not act by breaking disulfide bonds in situ. Instead, it works by altering the synthesis of glycoproteins in the mucus-secreting cells (mucoregulatory action). **High-Yield Clinical Pearls for NEET-PG:** * **Antidote Use:** Beyond its respiratory use, NAC is the specific antidote for **Paracetamol (Acetaminophen) poisoning** as it replenishes glutathione stores. * **Administration:** NAC can be administered via inhalation (nebulization) for respiratory conditions or orally/IV for toxicity. * **Adverse Effect:** When inhaled, NAC can trigger **bronchospasm**, especially in asthmatic patients; it is often co-administered with a bronchodilator. * **Renal Protection:** NAC is sometimes used to prevent **Contrast-Induced Nephropathy (CIN)** in high-risk patients.

Question 216: All of the following drugs can precipitate an acute attack of asthma except?

A. Phenylbutazone
B. Naproxen
C. Glucocorticoids (Correct Answer)
D. Aspirin

Explanation: **Explanation:** The correct answer is **Glucocorticoids**. In fact, glucocorticoids are the mainstay of treatment for bronchial asthma due to their potent anti-inflammatory properties. **1. Why Glucocorticoids are the correct answer:** Glucocorticoids (e.g., Prednisolone, Fluticasone) inhibit the enzyme **Phospholipase A2** via the synthesis of lipocortin (annexin-1). This action blocks the entire arachidonic acid cascade, preventing the production of both Prostaglandins and **Leukotrienes**. Since leukotrienes are potent bronchoconstrictors, glucocorticoids effectively reduce airway inflammation and hyperreactivity rather than precipitating an attack. **2. Why the other options are incorrect:** * **Aspirin, Naproxen, and Phenylbutazone:** These are all Non-Steroidal Anti-Inflammatory Drugs (NSAIDs). They work by inhibiting the **Cyclooxygenase (COX)** enzyme. * **Mechanism of Bronchospasm:** When the COX pathway is blocked, the metabolism of arachidonic acid is "shunted" toward the **Lipoxygenase (LOX) pathway**. This leads to an overproduction of **Cysteinyl Leukotrienes (LTC4, LTD4, LTE4)**, which cause intense bronchoconstriction, mucus secretion, and edema. This clinical phenomenon is known as **Aspirin-Exacerbated Respiratory Disease (AERD)** or Samter’s Triad. **High-Yield Clinical Pearls for NEET-PG:** * **Samter’s Triad:** Consists of Asthma, Aspirin sensitivity, and Nasal polyps. * **Safe Alternatives:** In patients with aspirin-sensitive asthma, **Paracetamol (Acetaminophen)** is generally considered the safest analgesic at low doses. * **Other drugs to avoid in Asthma:** Non-selective Beta-blockers (e.g., Propranolol) due to B2-receptor blockade, and Cholinergic drugs (e.g., Pilocarpine). * **Drug of Choice:** Inhaled Corticosteroids (ICS) are the drug of choice for the prophylactic management of persistent asthma.

Question 217: Vitamin K is a cofactor in which of the following biochemical reactions?

A. Carboxylation (Correct Answer)
B. Hydroxylation
C. Deamination
D. Hydrolysis

Explanation: **Explanation:** Vitamin K serves as an essential cofactor for the enzyme **gamma-glutamyl carboxylase**. This enzyme is responsible for the **post-translational modification** of specific glutamate residues into gamma-carboxyglutamate (Gla) on certain proteins. This process, known as **carboxylation**, allows these proteins to bind calcium ions ($Ca^{2+}$), which is a prerequisite for their activation and binding to phospholipid surfaces during the coagulation cascade. The primary targets of this reaction are: * **Clotting Factors:** II (Prothrombin), VII, IX, and X. * **Anticoagulant Proteins:** Protein C and Protein S. * **Bone Proteins:** Osteocalcin. **Analysis of Incorrect Options:** * **B. Hydroxylation:** This reaction is typically associated with **Vitamin C** (ascorbic acid), which acts as a cofactor for the hydroxylation of proline and lysine residues during collagen synthesis. * **C. Deamination:** This involves the removal of an amino group from an amino acid, usually mediated by transaminases and dehydratases (often requiring Vitamin B6), not Vitamin K. * **D. Hydrolysis:** This is the chemical breakdown of a compound due to reaction with water, catalyzed by hydrolases (e.g., digestive enzymes), and does not require Vitamin K as a cofactor. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism of Warfarin:** Warfarin acts as a Vitamin K antagonist by inhibiting **Vitamin K Epoxide Reductase (VKOR)**, preventing the recycling of Vitamin K and thus inhibiting the carboxylation of Factors II, VII, IX, and X. * **Bridge Therapy:** Because Protein C (an anticoagulant) has a shorter half-life than the procoagulant factors, a transient hypercoagulable state can occur when starting Warfarin, necessitating "bridging" with Heparin. * **Newborns:** Neonates are Vitamin K deficient due to sterile guts and poor placental transfer; hence, a prophylactic IM injection of Vitamin K is given at birth to prevent **Hemorrhagic Disease of the Newborn**.

Question 218: Which of the following drugs is approved for the treatment of cystic fibrosis specifically in patients with the G551D mutation?

A. Biostrophin
B. Peginesatide
C. Lumacaftor
D. Ivacaftor (Correct Answer)

Explanation: **Explanation:** **1. Why Ivacaftor is Correct:** Cystic Fibrosis (CF) is caused by mutations in the **CFTR (Cystic Fibrosis Transmembrane Conductance Regulator)** gene, which codes for a chloride channel. The **G551D mutation** is a "class III" or "gating" mutation, where the channel reaches the cell surface but fails to open properly. **Ivacaftor** is a **CFTR potentiator**; it binds to the defective channel and increases the probability that it will open, thereby restoring chloride transport and fluid balance. It was the first drug approved to treat the underlying cause of CF rather than just the symptoms. **2. Why the Other Options are Incorrect:** * **Biostrophin:** This is not a standard pharmacological agent used in CF; it is likely a distractor name (possibly confused with Dystrophin related to Muscular Dystrophy). * **Peginesatide:** This is an erythropoiesis-stimulating agent (ESA) formerly used for anemia in chronic kidney disease, not respiratory disease. * **Lumacaftor:** This is a **CFTR corrector**. It is used for the **F508del mutation** (the most common CF mutation), where the protein is misfolded and fails to reach the cell membrane. Lumacaftor helps the protein reach the surface, but it is typically used in combination with Ivacaftor (Orkambi®). **3. NEET-PG High-Yield Pearls:** * **Ivacaftor:** Specific for G551D (Gating mutation). * **Lumacaftor/Tezacaftor:** Correctors for F508del (Processing mutation). * **Trikafta:** A triple combination (Elexacaftor + Tezacaftor + Ivacaftor) now used for patients with at least one F508del mutation. * **Diagnosis:** Sweat Chloride Test (>60 mEq/L) remains the gold standard. * **Other CF Drugs:** Inhaled **Dornase alfa** (cleaves DNA in sputum to decrease viscosity) and **Inhaled Tobramycin** (for *Pseudomonas* prophylaxis).

Question 219: What is the drug of choice for the treatment of type 2 Brittle Asthma?

A. Beta-adrenergic agonist
B. Inhaled corticosteroids
C. Antileukotrienes
D. Subcutaneous epinephrine (Correct Answer)

Explanation: Explanation: Brittle Asthma is a rare but severe form of asthma characterized by wide variations in Peak Expiratory Flow (PEF) despite high doses of inhaled therapy. It is classified into two types: * Type 1: Persistent wide variability in PEF despite intense medical therapy. * Type 2: Sudden, unpredictable, and life-threatening falls in PEF (attacks) occurring on a background of otherwise well-controlled asthma. Why Subcutaneous Epinephrine is Correct: Type 2 Brittle Asthma is characterized by "sudden-onset" attacks that can lead to respiratory arrest within minutes. Subcutaneous Epinephrine is the drug of choice because it provides rapid systemic bronchodilation and stabilizes mast cells [1]. In these patients, the deterioration is so rapid that inhaled medications may not reach the distal airways effectively, and systemic administration becomes life-saving. Analysis of Incorrect Options: * A. Beta-adrenergic agonists: While inhaled SABA (Salbutamol) is the mainstay for acute asthma, it is often insufficient for the "thunderclap" bronchoconstriction seen in Type 2 Brittle Asthma. * B. Inhaled corticosteroids: These are used for long-term maintenance (prophylaxis) to reduce airway inflammation but have no role in the immediate management of an acute, brittle attack. * C. Antileukotrienes: These are add-on therapies for chronic management (especially in aspirin-sensitive asthma) and are not indicated for emergency rescue. NEET-PG High-Yield Pearls: * Type 1 Brittle Asthma Management: Often requires a subcutaneous infusion of Terbutaline via a pump. * Epinephrine Dose: In acute severe asthma/anaphylaxis, the standard dose is 0.3-0.5 mg (1:1000 dilution) [1]. * Key Distinction: Type 1 is about "variability," while Type 2 is about "unpredictable sudden crashes."

Question 220: Which of the following is false about salmeterol?

A. Regular use may worsen asthma
B. First long acting selective beta-2 agonist
C. Effective for acute asthmatic attacks (Correct Answer)
D. More beta-2 selective agonist than salbutamol

Explanation: **Explanation:** Salmeterol is a **Long-Acting Beta-2 Agonist (LABA)**. The correct answer is **C** because salmeterol is **not effective for acute asthmatic attacks**. **1. Why Option C is False (The Correct Answer):** Salmeterol has a **slow onset of action** (approximately 15–20 minutes) compared to Short-Acting Beta-2 Agonists (SABAs) like Salbutamol, which work within minutes. Because it does not provide immediate bronchodilation, it is contraindicated as a rescue medication. Using it during an acute attack can delay necessary emergency treatment. **2. Analysis of Other Options:** * **Option A:** Regular use of LABAs as monotherapy is associated with a risk of masking underlying inflammation, potentially leading to severe asthma exacerbations or "worsening" of the disease. This is why they are now strictly recommended to be used only in combination with **Inhaled Corticosteroids (ICS)**. * **Option B:** Salmeterol was indeed the first selective LABA introduced for clinical use, providing bronchodilation for over 12 hours. * **Option C:** Salmeterol is significantly more selective for $\beta_2$ receptors than Salbutamol. Its long lipophilic side chain allows it to anchor to the "exosite" of the $\beta_2$ receptor, providing sustained activation. **High-Yield Clinical Pearls for NEET-PG:** * **SMART Therapy:** Current GINA guidelines recommend Single Maintenance and Reliever Therapy using **Formoterol** (a LABA with a *fast* onset) + ICS, but **never** Salmeterol for relief. * **Duration:** Salmeterol acts for >12 hours due to its high lipid solubility. * **Black Box Warning:** LABAs should never be used as monotherapy in asthma due to the risk of asthma-related death (always combine with ICS).

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

Practice Questions

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