A 60-year-old male with hypertension is prescribed chlorthalidone. Chlorthalidone works by:

Correct Answer: A

Rationale: The correct answer is A: Inhibiting sodium reabsorption in the kidneys. Chlorthalidone is a thiazide diuretic that works by acting on the distal convoluted tubule of the kidneys to inhibit sodium reabsorption. This leads to increased excretion of sodium and water, resulting in decreased blood volume and reduced blood pressure. Blocking calcium channels (B) is the mechanism of action for calcium channel blockers, not thiazide diuretics. Thiazide diuretics do not directly inhibit the action of aldosterone (C), which is a hormone that regulates sodium and potassium balance. Thiazides can cause potassium loss, but they do not directly increase the excretion of potassium (D).

Correct Answer: A

Rationale: The correct answer is A: Blocking beta-1 adrenergic receptors in the heart. Atenolol is a beta-blocker that primarily acts on beta-1 receptors in the heart, reducing heart rate and blood pressure. This helps in managing hypertension. Beta-2 receptors are predominantly found in the lungs, so choice B is incorrect. Choice C refers to calcium channel blockers, not atenolol. Choice D is related to diuretics, not beta-blockers like atenolol. Thus, the correct answer is A due to atenolol's specific action on beta-1 receptors in the heart.

Correct Answer: A

Rationale: The correct answer is A because sitagliptin works by inhibiting the enzyme dipeptidyl peptidase-4 (DPP-4), which breaks down incretin hormones like GLP-1 and GIP. By inhibiting DPP-4, sitagliptin prolongs the action of these hormones, leading to increased insulin release and decreased glucagon secretion, ultimately lowering blood glucose levels. Choices B, C, and D are incorrect because sitagliptin does not directly increase insulin secretion from the pancreas, inhibit glucose absorption in the intestines, or increase renal glucose excretion.

Correct Answer: A

Rationale: The correct answer is A: Alprazolam. Alprazolam is a benzodiazepine commonly used for treating acute anxiety due to its fast onset of action. It works by enhancing the effects of GABA neurotransmitters, leading to calming effects. Citalopram and Venlafaxine are antidepressants used for long-term treatment of anxiety disorders, not for acute episodes. Zolpidem is a sedative-hypnotic mainly used for insomnia, not anxiety.

Correct Answer: B

Rationale: The correct answer is B: Propranolol. Propranolol is a beta-blocker commonly prescribed for migraine prevention due to its ability to reduce the frequency and severity of migraine attacks by affecting blood vessels and neurotransmitters. Sumatriptan (A) is used for acute migraine treatment, not prevention. Ibuprofen (C) is an over-the-counter pain reliever for acute relief, not prevention. Lorazepam (D) is a benzodiazepine used for anxiety, not migraine prevention. Propranolol is the most appropriate choice for long-term migraine management.