Which of the following drugs may cause reversible gynecomastia?

Correct Answer: C

Rationale: Rationale: Cimetidine is an H2 receptor antagonist that can cause reversible gynecomastia by inhibiting androgen receptors. This leads to increased estrogen levels and breast tissue growth in males. Omeprazole (A), Pirenzepine (B), and Sucralfate (D) are not associated with gynecomastia as they do not affect hormone levels in the same way as cimetidine.

Correct Answer: A

Rationale: The correct answer is A: TRUE. Calcium channel blockers reduce the inward movement of calcium during the action potential in cardiac muscle cells, leading to a decrease in the intracellular calcium concentration. This results in a direct negative inotropic effect by reducing the force of contraction of the heart muscle. Choices B and D are incorrect because calcium channel blockers do indeed have direct negative inotropic effects. Choice C is incorrect as well because not all choices are correct; only choice A is accurate based on the mechanism of action of calcium channel blockers in cardiac muscle cells.

Correct Answer: C

Rationale: Rationale: 1. Losartan is a non-peptide angiotensin II receptor antagonist. 2. Clonidine is a centrally acting alpha-2 adrenergic agonist. 3. Captopril is an ACE inhibitor. 4. Diazoxide is a potassium channel activator, used for hyperinsulinism. Therefore, the correct answer is C, as it specifically targets angiotensin II receptors, unlike the other choices.

Correct Answer: D

Rationale: The correct answer is D because many hormones actually exert their effects by interacting with specific receptors on the cell membrane rather than acting directly on subcellular membranes. This interaction triggers a series of intracellular events that lead to a cellular response. Option A is true as hormones indeed interact with specific receptors on cell walls. Option B is true as cyclic AMP is a common second messenger system utilized by hormones. Option C is true as many hormones stimulate adenylcyclase enzyme as part of their signaling pathway.

Correct Answer: A

Rationale: The correct answer is A, Repaglinide (Prandin), as it is not a biguanide but a meglitinide used for managing type 2 diabetes by stimulating insulin release. Metformin is a biguanide commonly used as a first-line treatment for type 2 diabetes due to its efficacy and safety profile. Phenformin is a biguanide that was withdrawn from the market due to its association with lactic acidosis. Glipizide is a sulfonylurea, not a biguanide, and works by stimulating insulin release from the pancreas. Therefore, A is the correct answer as it is not an oral hypoglycemic biguanide.