Answer: C. Cimetidine

Explanation: Cimetidine, an H2 receptor antagonist, is known to cause reversible gynecomastia by interfering with hormonal balance, leading to temporary breast tissue enlargement in males.

Answer: D. Metoclopropamide

Explanation: Unlike isoniazid, dapsone, and hydralazine, metoclopropamide is not primarily metabolized by acetylation, which affects its pharmacokinetic profile and side-effect potential.

Answer: A. Adenosine

Explanation: Adenosine has an extremely short biological half-life (seconds) due to rapid uptake and metabolism, making it useful in acute cardiac interventions such as terminating supraventricular tachycardia.

Answer: A. Glutathione

Explanation: Nitroglycerine undergoes biotransformation via denitration primarily through conjugation with glutathione, which inactivates the drug and facilitates its elimination.

Answer: D. All of the given

Explanation: Amphotericin B, cisplatin, and even some ACE inhibitors are known for their nephrotoxic effects. Their use requires careful monitoring of kidney function to prevent renal damage.

Answer: B. Lovastatin and Simvastatin

Explanation: Lovastatin and Simvastatin are administered as inactive lactone prodrugs. They require in vivo hydrolysis to form the active beta‐hydroxy acid, which inhibits HMG-CoA reductase in cholesterol biosynthesis.

Answer: A. Retigabine

Explanation: Retigabine is a potassium channel opener that acts by stabilizing the open state of the channel, thereby hyperpolarizing neurons. It is used as an anticonvulsant to reduce neuronal excitability.

Answer: C. Acarbose

Explanation: Acarbose is a complex polysaccharide that acts as an alpha-glucosidase inhibitor. It delays carbohydrate digestion and absorption, which helps control postprandial blood glucose levels in diabetic patients.

Answer: A. Serotonin 5-HT3 receptor

Explanation: The serotonin 5-HT3 receptor plays a critical role in chemotherapy-induced vomiting. Blocking this receptor with antagonists can prevent nausea and vomiting, improving patient comfort during cancer treatment.

Answer: B. Sink condition

Explanation: Protein binding of drugs creates a reservoir effect known as the 'sink condition,' where the bound drug maintains a concentration gradient that facilitates continuous absorption of the free drug from the gastrointestinal tract.

Answer: A. It is soluble in water but insoluble in organic solvents

Explanation: Cannabidiol is actually lipophilic and poorly soluble in water. The statement claiming it is soluble in water is incorrect, making option (a) the wrong statement regarding its solubility.

Answer: B. Cisplatin

Explanation: Cisplatin is a potent chemotherapeutic agent known for its nephrotoxicity. Its renal toxicity limits its dosage and necessitates protective measures such as hydration to minimize kidney damage.

Answer: B. Clozapine

Explanation: Clozapine is an atypical antipsychotic that does not belong to the phenothiazine class. Phenothiazines typically have a tricyclic structure, whereas clozapine has a different chemical framework.

Answer: A. Metabotropic

Explanation: Metabotropic receptors, such as G protein-coupled receptors (GPCRs), have a heptahelical structure. They span the cell membrane seven times and play crucial roles in signal transduction.

Answer: C. Streptococcal infection

Explanation: Metronidazole is used primarily for anaerobic infections, Helicobacter pylori, and pseudomembranous colitis; it is not effective against streptococcal infections which require other antibiotics.

Answer: A. Diazepam

Explanation: Diazepam is a long-acting benzodiazepine, whereas alprazolam, midazolam, and lorazepam are classified as short-acting due to their faster onset and shorter duration of action.

Answer: A. Oxazolidinone

Explanation: Linezolid belongs to the oxazolidinone class of antibiotics and works by inhibiting bacterial protein synthesis. It is particularly effective against gram-positive pathogens, including resistant strains such as MRSA.

Answer: B. Decrease secretion of aldosterone

Explanation: ACE inhibitors reduce the conversion of angiotensin I to angiotensin II, leading to decreased aldosterone secretion. This results in lower blood pressure and reduced fluid retention.

Answer: B. Aziridine ring

Explanation: Cyclophosphamide is metabolized in the liver to produce an aziridine ring intermediate, which is responsible for its cytotoxic activity by forming cross-links in DNA, leading to cell death.

Answer: D. Erythromycin

Explanation: Erythromycin acts as a motilin receptor agonist, stimulating gastrointestinal motility. It is sometimes used off-label to treat gastroparesis by enhancing the movement of food through the digestive tract.