A patient with hypertension is prescribed hydrochlorothiazide. The mechanism of action of hydrochlorothiazide involves:

Correct Answer: A

Rationale: Step 1: Hydrochlorothiazide is a thiazide diuretic. Step 2: Thiazide diuretics work by inhibiting sodium reabsorption in the kidneys. Step 3: By blocking sodium reabsorption, hydrochlorothiazide increases water excretion, reducing blood volume and lowering blood pressure. Step 4: Therefore, the correct answer is A: Inhibiting sodium reabsorption in the kidneys. Summary: - Option B (Blocking calcium channels) is incorrect because hydrochlorothiazide does not affect calcium channels. - Option C (Increasing the excretion of potassium) is incorrect as thiazide diuretics can cause hypokalemia by increasing potassium excretion. - Option D (Relaxing vascular smooth muscle) is incorrect as this is not the primary mechanism of action of hydrochlorothiazide.

Correct Answer: B

Rationale: The correct answer is B: Increasing serotonin and norepinephrine in the brain. Tramadol is a synthetic opioid analgesic that acts by binding to mu-opioid receptors and also inhibiting the reuptake of serotonin and norepinephrine. This dual mechanism of action helps alleviate pain by enhancing the effects of these neurotransmitters in the brain. Choices A, C, and D are incorrect because tramadol primarily affects serotonin and norepinephrine levels rather than blocking opioid receptors, inhibiting dopamine reuptake, or decreasing substance P in the spinal cord.

Correct Answer: C

Rationale: Rationale for Choice C: In noncompetitive antagonism, the antagonist binds irreversibly to a site different from the agonist binding site, preventing agonist binding. Increasing agonist concentration cannot overcome this as the antagonist blocks the receptor irreversibly. This results in a fixed maximum response. Summary: A: Incorrect. The potency of the drug may change due to noncompetitive antagonism. B: Incorrect. Noncompetitive antagonism does not affect the number of receptors available to bind the agonist. D: Incorrect. Choice C is correct, making this statement wrong.

Correct Answer: D

Rationale: The correct answer is D: Induction of powerful uterine contracture. Ergonovine is a uterotonic agent that works by stimulating uterine contractions, which helps control postpartum hemorrhage due to uterine atony. The drug acts directly on the smooth muscle of the uterus, leading to increased tone and decreased bleeding. A: Selective constriction of uterine arteries is incorrect because ergonovine primarily acts on the uterine muscle itself, not the blood vessels supplying the uterus. B: Endothelin release in the uterine vascular bed is incorrect as ergonovine does not directly affect endothelin release. C: Platelet aggregation in the uterine vascular bed is incorrect as ergonovine's action is not related to platelet aggregation but rather to uterine muscle contraction. In summary, the therapeutic effect of ergonovine in this patient is mediated by its ability to induce powerful uterine contr

Correct Answer: C

Rationale: The correct answer is C: Ergotamine. Ergotamine is known to cause vasoconstriction, leading to decreased blood flow to extremities, resulting in numbness and tingling. Ibuprofen is a nonsteroidal anti-inflammatory drug and does not typically cause numbness and tingling. Valproic acid is used for epilepsy and mood disorders. Propranolol is a beta-blocker used for hypertension and migraines but is not associated with numbness and tingling in extremities.