All of the following antimycobacterial drugs have a bactericidal effect EXCEPT:

Correct Answer: A

Rationale: The correct answer is A: Pyrazinamide. Pyrazinamide is not a bactericidal drug but rather a bacteriostatic drug. It inhibits the growth of mycobacteria rather than directly killing them. Streptomycin, Rifampin, and Isoniazid are all bactericidal drugs that directly kill mycobacteria. Streptomycin disrupts protein synthesis, Rifampin inhibits RNA synthesis, and Isoniazid inhibits mycolic acid synthesis in mycobacteria, leading to their death. Therefore, Pyrazinamide is the only drug among the options that does not have a bactericidal effect.

Correct Answer: B

Rationale: The correct answer is B: Triamterene. Triamterene is a potassium-sparing diuretic that helps prevent new stone production by inhibiting sodium reabsorption in the kidneys, reducing the risk of stone formation. Mannitol (A) is an osmotic diuretic used for specific medical conditions, not for preventing stone formation. Conivaptan (C) is a vasopressin receptor antagonist primarily used for hyponatremia, not for preventing stone formation. Acetazolamide (D) is a carbonic anhydrase inhibitor that can help with certain types of kidney stones but is not typically used for preventing new stone production.

Correct Answer: A

Rationale: Verapamil is the correct choice as it is a calcium channel blocker that can help prevent cerebral vasospasm, reducing the risk of delayed cerebral ischemia in subarachnoid hemorrhage. Verapamil works by dilating blood vessels, improving blood flow to the brain. Isosorbide mononitrate (B) is a nitrate used for angina, not specifically for cerebral ischemia. Propranolol (C) is a beta-blocker and Dobutamine (D) is a positive inotrope that are not directly indicated for preventing cerebral ischemia in this context.

Correct Answer: C

Rationale: Failed to generate a rationale of 500+ characters after 5 retries.

Correct Answer: B

Rationale: Failed to generate a rationale of 500+ characters after 5 retries.