Respiratory System Drugs Practice Questions

Q: Most common side effect of salbutamol is:

Tremors. **Explanation:** **Salbutamol** is a Short-Acting Beta-2 Agonist (SABA) used primarily as a bronchodilator. **1. Why Tremors are the Correct Answer:** The most common side effect of Salbutamol is **skeletal muscle tremors**, specifically involving the hands. While Salbutamol is selective for $\beta_2$ receptors, these receptors are not only located in the bronchial smooth muscle but also on the **skeletal muscle fibers**. Activation of $\beta_2$ receptors in the muscles increases the speed of contraction and alters spindle sensitivity, leading to fine tremors. This is a dose-dependent effect and is more pronounced with oral administration than inhalation. **2. Why Incorrect Options are Wrong:** * **Hypertension:** Salbutamol typically causes peripheral vasodilation (via $\beta_2$ receptors in blood vessels), which can lead to a slight decrease in diastolic blood pressure and compensatory **tachycardia**, rather than hypertension. * **Rhinorrhea:** This is not a recognized side effect of $\beta_2$ agonists. In fact, sympathomimetics are more likely to cause nasal decongestion. * **Headache:** While headache can occur due to vasodilation, it is significantly less common than tremors. **3. High-Yield Clinical Pearls for NEET-PG:** * **Metabolic Effects:** Salbutamol can cause **Hypokalemia** (due to the shift of $K^+$ into cells), which is why it is sometimes used in the emergency management of hyperkalemia. * **Cardiac Effects:** It can cause tachycardia and palpitations (due to $\beta_1$ cross-reactivity and reflex tachycardia). * **Tolerance:** Overuse can lead to "downregulation" or desensitization of $\beta_2$ receptors. * **Drug of Choice:** Salbutamol remains the drug of choice for **acute episodes** (rescue therapy) of bronchial asthma.

Q: Sildenafil, a phosphodiesterase-5 inhibitor, can be used for which of the following conditions?

Pulmonary hypertension. **Explanation:** **Sildenafil** is a potent and selective inhibitor of **Phosphodiesterase-5 (PDE-5)**. In the lungs, PDE-5 is responsible for the degradation of cyclic Guanosine Monophosphate (cGMP) [1]. By inhibiting this enzyme, Sildenafil increases cGMP levels, which leads to smooth muscle relaxation and potent **vasodilation of the pulmonary vascular bed** [1], [2]. This reduces pulmonary artery pressure and improves exercise capacity, making it a first-line oral therapy for **Pulmonary Arterial Hypertension (PAH)** [1]. **Analysis of Incorrect Options:** * **B & C (Essential and Malignant Hypertension):** Sildenafil causes systemic vasodilation, but its effect on systemic blood pressure is relatively modest compared to its effect on the pulmonary vasculature. It is not indicated for the management of systemic hypertension or hypertensive emergencies (Malignant HTN), where drugs like ACE inhibitors, CCBs, or Sodium Nitroprusside are preferred. * **D (Hypertension in Pregnancy):** The drugs of choice for hypertension in pregnancy (Preeclampsia/Gestational HTN) are **Labetalol (DOC)**, Methyldopa, or Hydralazine. Sildenafil is not standard therapy for this condition. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism:** Increases cGMP $\rightarrow$ Nitric Oxide (NO) mediated vasodilation [1], [2]. * **Other Indications:** Erectile Dysfunction (original use) [3], [4]. * **Contraindication:** Must **NEVER** be co-administered with **Nitrates** (e.g., Nitroglycerin) as it can cause life-threatening hypotension due to synergistic increases in cGMP. * **Side Effects:** Blue-tinted vision (Cyanopsia) due to cross-inhibition of PDE-6 in the retina, headache, and flushing. * **Tadalafil:** Another PDE-5 inhibitor used for PAH with a longer half-life than Sildenafil [1].

Q: Filgrastim is used for the treatment of which condition?

Neutropenia. **Explanation:** **Filgrastim** is a recombinant human **Granulocyte Colony-Stimulating Factor (G-CSF)**. It acts by binding to specific receptors on hematopoietic cells, stimulating the proliferation, differentiation, and activation of committed neutrophil progenitors. **1. Why Neutropenia is the Correct Answer:** Filgrastim is primarily used to accelerate the recovery of neutrophil counts in patients experiencing **neutropenia**. This is most commonly seen in patients receiving myelosuppressive cancer chemotherapy, those undergoing bone marrow transplantation, or patients with severe chronic neutropenia. By increasing the Absolute Neutrophil Count (ANC), it reduces the duration of fever and the risk of life-threatening infections. **2. Why the Other Options are Incorrect:** * **Anemia:** This is a deficiency of red blood cells or hemoglobin. It is treated with Erythropoiesis-Stimulating Agents (ESAs) like **Erythropoietin** or Darbepoetin, not G-CSF. * **Polycythemia:** This is an abnormal increase in RBCs. Treatment involves phlebotomy or myelosuppressive agents (like Hydroxyurea), not growth factors. * **Neutrophilia:** This refers to an abnormally high neutrophil count (often due to infection or inflammation). Administering Filgrastim would worsen this condition. **3. High-Yield Clinical Pearls for NEET-PG:** * **Side Effects:** The most common side effect of Filgrastim is **bone pain** (due to marrow expansion). * **Sargramostim:** This is a recombinant **GM-CSF** (Granulocyte-Macrophage CSF) which stimulates both neutrophils and macrophages. * **Pegfilgrastim:** A pegylated form of Filgrastim with a much longer half-life, allowing for once-per-chemotherapy-cycle dosing. * **Timing:** It should not be administered within 24 hours before or after chemotherapy to avoid killing rapidly dividing progenitor cells.

Q: Diphenhydramine used as an antitussive is a type of:

Antihistamine. **Explanation:** **1. Why the Correct Answer is Right:** Diphenhydramine is a **first-generation H1-receptor antagonist** (Antihistamine). While primarily used for allergic reactions, it possesses significant **antitussive (cough suppressant)** properties. Its mechanism of action in cough suppression is primarily **central**, acting on the cough center in the medulla to increase the cough threshold. Additionally, its potent **anticholinergic (antimuscarinic)** effects help reduce secretions in the upper airways, which further aids in relieving coughs associated with post-nasal drip and common colds. **2. Why the Other Options are Incorrect:** * **A. Central opioid agonist:** This refers to drugs like **Codeine** and **Pholcodine**, which suppress cough by acting on μ-opioid receptors in the brain. Diphenhydramine is non-opioid. * **B. NMDA blocker:** This refers to **Dextromethorphan**, a common non-opioid antitussive that acts as an NMDA receptor antagonist. * **C. Mucolytic:** These are drugs like **Ambroxol, Bromhexine, or N-acetylcysteine** that break down the chemical structure of mucus to make it less viscous; they do not suppress the cough reflex. **3. NEET-PG High-Yield Pearls:** * **Sedation:** Being a first-generation antihistamine, Diphenhydramine crosses the blood-brain barrier, causing significant sedation (a common side effect). * **Anticholinergic Side Effects:** Watch for "dry mouth, urinary retention, and blurred vision" in clinical vignettes. * **Other First-Gen Antitussives:** Chlorpheniramine and Promethazine are also used in cough syrups for their sedative and drying effects. * **Drug of Choice:** For a dry, hacking cough without a known cause, Codeine or Dextromethorphan are generally preferred, but Diphenhydramine is specific for coughs triggered by upper respiratory allergies.

Q: What is the commonest side effect of antihistamines?

Sedation. **Explanation:** **1. Why Sedation is the Correct Answer:** Antihistamines, specifically **First-Generation H1-receptor antagonists** (e.g., Diphenhydramine, Chlorpheniramine, Promethazine), are highly lipophilic and readily cross the blood-brain barrier (BBB). Once in the CNS, they block H1 receptors in the tuberomammillary nucleus of the hypothalamus, which is responsible for maintaining wakefulness and alertness. This blockade leads to **sedation**, which is the most frequent and clinically significant side effect of these drugs. **2. Why the Other Options are Incorrect:** * **B. Tinnitus:** While some drugs (like high-dose Aspirin or Aminoglycosides) are known for ototoxicity, tinnitus is not a characteristic or common side effect of antihistamines. * **C. Euphoria:** Antihistamines typically cause CNS depression rather than stimulation. Euphoria is rare; in fact, some patients may experience "dysphoria" or, in children, "paradoxical excitation." * **D. Lassitude:** Lassitude (a state of physical or mental weariness) is a common side effect of antihistamines, but it is considered a component of the broader sedative effect. In comparative clinical frequency, **sedation** is the primary and most commonly reported complaint. **3. High-Yield NEET-PG Clinical Pearls:** * **Second-Generation Antihistamines** (e.g., Cetirizine, Loratadine, Fexofenadine) are less lipophilic and have poor CNS penetration, making them "non-sedating." * **Fexofenadine** is considered the least sedating (purely non-sedating) as it is a substrate for the P-glycoprotein efflux pump. * **Anticholinergic effects:** First-generation H1 blockers also block muscarinic receptors, leading to dry mouth, blurred vision, and urinary retention. * **Drug of choice for Motion Sickness:** Promethazine or Diphenhydramine (due to central anticholinergic action).

Q: All of the following drugs may be useful in the acute exacerbation of bronchial asthma EXCEPT?

Ipratropium. ### Explanation The management of acute exacerbation of bronchial asthma focuses on rapid bronchodilation and reducing airway inflammation. **Why Ipratropium is the "Except" (Correct Answer):** While Ipratropium bromide (an inhaled anticholinergic) is frequently used in the emergency department as an **adjunct** to Beta-2 agonists, it is **never used alone** for acute relief. However, in the context of this specific question, **Cromolyn sodium** is actually the most inappropriate drug for acute attacks. *Note: There appears to be a discrepancy in the provided key. In standard pharmacological teaching, **Cromolyn sodium** is the classic "Except" because it is a mast cell stabilizer that prevents degranulation; it has no bronchodilatory properties and is strictly for prophylaxis. If the key identifies Ipratropium, it may be due to its slower onset compared to Salbutamol, but clinically, Cromolyn is the drug contraindicated in acute settings.* **Analysis of Options:** * **Salbutamol (SABA):** The drug of choice for acute attacks. It provides rapid bronchodilation by stimulating $\beta_2$ receptors. * **Hydrocortisone:** A systemic corticosteroid used in acute severe asthma to reduce airway inflammation and upregulate $\beta_2$ receptors. * **Ipratropium:** An M3 receptor antagonist. When combined with Salbutamol (e.g., Duolin), it provides synergistic bronchodilation and reduces hospitalization rates in severe exacerbations. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice (Acute):** Inhaled Salbutamol. * **Drug of Choice (Prophylaxis):** Inhaled Corticosteroids (e.g., Fluticasone). * **Mast Cell Stabilizers (Cromolyn):** Ineffective once an attack has started; can actually worsen bronchospasm due to irritation if used during an acute episode. * **Magnesium Sulfate:** Used intravenously in life-threatening asthma non-responsive to initial therapy.

Question 1

Which of the following antihistamines is free of arrhythmogenic potential?

Accepted Answer

Loratadine

Answer

Terfenadine

Answer

Fexofenadine

Answer

Ebastine

Question 2

Which of the following statements regarding methylxanthines is true?

Accepted Answer

They block the receptor-mediated actions of adenosine.

Answer

They can enhance water and electrolyte excretion.

Answer

They can relax bronchial smooth muscles.

Answer

Long-term ingestion can produce tolerance and physical dependence.

Question 3

Most common side effect of salbutamol is:

Accepted Answer

Tremors

Answer

Hypertension

Answer

Rhinorrhea

Answer

Headache

Question 4

Sildenafil, a phosphodiesterase-5 inhibitor, can be used for which of the following conditions?

Accepted Answer

Pulmonary hypertension

Answer

Essential hypertension

Answer

Malignant hypertension

Answer

Hypertension in pregnancy

Question 5

Filgrastim is used for the treatment of which condition?

Accepted Answer

Neutropenia

Answer

Anemia

Answer

Polycythemia

Answer

Neutrophilia

Question 6

Which of the following is a directly acting cough suppressant?

Accepted Answer

Dextromethorphan

Answer

Bromhexine

Answer

Acetylcysteine

Answer

Carbetapentane

Question 7

Diphenhydramine used as an antitussive is a type of:

Accepted Answer

Antihistamine

Answer

Central opioid agonist

Answer

NMDA blocker

Answer

Mucolytic

Question 8

A 25-year-old man experiences exercise-induced bronchospasm, particularly in cold weather. He takes a medication 15 minutes prior to anticipated exercise which helps prevent asthmatic attacks but does not produce bronchodilation. Which drug does he take?

Accepted Answer

Cromolyn sodium

Answer

Short-acting beta-agonist inhaler

Answer

Inhaled glucocorticoid

Answer

Omalizumab

Question 9

What is the commonest side effect of antihistamines?

Accepted Answer

Sedation

Answer

Tinnitus

Answer

Euphoria

Answer

Lassitude

Question 10

All of the following drugs may be useful in the acute exacerbation of bronchial asthma EXCEPT?

Accepted Answer

Ipratropium

Answer

Cromolyn sodium

Answer

Hydrocortisone

Answer

Salbutamol

Respiratory System Drugs — MCQs

Respiratory System Drugs — MCQs

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