This drug both inhibits an enzyme and indirectly enhances clearance of low density lipoproteins (LDL):

Correct Answer: B

Rationale: Step 1: Lovastatin inhibits HMG-CoA reductase, an enzyme involved in cholesterol synthesis. Step 2: Inhibiting HMG-CoA reductase leads to upregulation of LDL receptors, enhancing LDL clearance. Step 3: Therefore, Lovastatin both inhibits an enzyme and indirectly enhances LDL clearance. Summary: A: Cholestyramine binds bile acids, not related to LDL clearance. C: Nicotinic acid primarily affects HDL levels, not directly related to LDL clearance. D: Probucol mainly acts by increasing HDL levels, not directly related to LDL clearance.

Correct Answer: B

Rationale: The correct answer is B: Thiazide diuretics. Thiazide diuretics act in the distal convoluted tubule by inhibiting the sodium-chloride symporter, leading to increased sodium and water excretion. This results in decreased blood volume and reduced blood pressure. Loop diuretics (A) act in the loop of Henle, potassium-sparing diuretics (C) act in the collecting duct, and carbonic anhydrase inhibitors (D) act in the proximal convoluted tubule. Thiazide diuretics are preferred for conditions like hypertension and edema due to their efficacy and site of action in the distal convoluted tubule.

Correct Answer: A

Rationale: The correct answer is A: Inhibition of transpeptidation in the bacterial cell wall. Penicillins work by inhibiting the enzyme transpeptidase, which is involved in the cross-linking of peptidoglycan chains in the bacterial cell wall. This leads to weakened cell walls, causing bacterial cell lysis. Choices B, C, and D are incorrect because penicillins do not inhibit beta-lactamase (choice B), activate endogenous proteases to destroy the cell wall (choice C), or activate endogenous phospholipases altering cell membrane permeability (choice D). The primary mechanism of action of penicillins is through interfering with cell wall synthesis, making choice A the correct answer.

Correct Answer: A

Rationale: Nitrofurantoin is the correct answer because it is a nitrofurane derivative with antibacterial properties, commonly used to treat urinary tract infections. Trimethoprim, Ciprofloxacin, and Nystatin are not nitrofurane derivatives and have different mechanisms of action, making them ineffective for this purpose.

Correct Answer: B

Rationale: The correct answer is B: Rimantadine. Rimantadine inhibits the uncoating of viral RNA by preventing the release of viral RNA into the host cell. This disrupts the replication process of the virus. Vidarabine (A) inhibits viral DNA polymerase, not viral RNA uncoating. Acyclovir (C) inhibits viral DNA polymerase as well. Didanozine (D) is an antiretroviral drug used in HIV treatment, not for inhibiting viral RNA uncoating.