Which of the following antianginal agents is a potassium channel opener:

Correct Answer: D

Rationale: Step-by-step rationale for D (Minoxidil) as the correct answer: 1. Minoxidil is a vasodilator used for hypertension. 2. It acts by opening potassium channels in vascular smooth muscle cells. 3. Opening potassium channels leads to hyperpolarization, causing relaxation. 4. This relaxation reduces peripheral vascular resistance, decreasing blood pressure. Summary: A (Dipyridamole) is a platelet inhibitor, not a potassium channel opener. B (Validol) is a mild cardiac sedative. C (Atenolol) is a beta-blocker. The correct answer is D (Minoxidil) because it directly acts on potassium channels to induce vasodilation.

Correct Answer: A

Rationale: The correct answer is A because glucagon is a hormone released by the pancreas in response to low blood sugar levels. Glucagon stimulates gluconeogenesis in the liver, which is the process of synthesizing glucose from non-carbohydrate sources like amino acids and glycerol. This helps increase blood glucose levels. Choice B is incorrect because glucagon actually inhibits the secretion of insulin by beta cells. Choice C is incorrect because glucagon does not inhibit glucose utilization by skeletal muscle; instead, it promotes the breakdown of glycogen to release glucose. Choice D is incorrect because glucagon does not inhibit the uptake of amino acids by cells; it actually promotes the breakdown of stored energy sources like glycogen and fat.

Correct Answer: A

Rationale: Prednisolone is the correct answer because it is a short- to medium-acting glucocorticoid, with a duration of action of about 12-36 hours. Dexamethasone is a long-acting glucocorticoid, with a duration of action of 36-72 hours. Triamcinolone is also a long-acting glucocorticoid with a duration of action of 12-36 hours. Therefore, choices B and C are incorrect. Choice D is incorrect because not all of the options are short- to medium-acting drugs.

Correct Answer: B

Rationale: The correct answer is B: Piperidines; i.e. Loratadine, Fexofenadine. Second-generation antihistamines like Loratadine and Fexofenadine belong to the piperidine category. Second-generation antihistamines are preferred over first-generation due to their lower sedative effects and longer duration of action. Alkylamines (A), Ethylenediamines (C), and Phenothiazines (D) are not classified as second-generation antihistamines and are associated with more sedation and anticholinergic side effects.

Correct Answer: D

Rationale: The correct answer is D because vitamin A does not act as a hormone involved in the regulation of calcium and phosphorus homeostasis. A: This statement is true as vitamin A is essential for the transmission of light stimuli to the brain through the formation of visual pigment in the retina. B: This statement is true as retinoic acid, a metabolite of vitamin A, plays a crucial role in regulating cell growth and differentiation in various tissues. C: This statement is true as retinoic acid is important during embryogenesis for proper development. In summary, vitamin A is not involved in the regulation of calcium and phosphorus homeostasis, making statement D the correct answer.