This drug weakly stimulates synthesis of very low density lipoproteins (VLDL):

Correct Answer: A

Rationale: Correct Answer: A: Cholestyramine (Questran) Rationale: Cholestyramine is a bile acid sequestrant that indirectly stimulates VLDL synthesis by interrupting enterohepatic circulation. It binds bile acids in the intestine, leading to increased hepatic cholesterol conversion to bile acids. This triggers compensatory upregulation of hepatic LDL and VLDL synthesis. Summary of other choices: B: Lovastatin (Mevacor) - Inhibits HMG-CoA reductase, reducing cholesterol synthesis. C: Gemfibrozil (Lopid) - Increases lipoprotein lipase activity, reducing VLDL levels. D: Probucol (Lorelco) - Reduces VLDL synthesis by inhibiting cholesterol ester transfer protein.

Correct Answer: B

Rationale: Loop diuretics inhibit the Na/K/2Cl cotransporter in the thick ascending loop of Henle, while thiazide diuretics act on the NaCl cotransporter in the distal convoluted tubule. Therefore, the correct answer is B. Loop diuretics (A) work differently by targeting a different transporter. Potassium-sparing diuretics (C) inhibit sodium channels in the collecting duct and distal nephron, not the NaCl cotransporter. Carbonic anhydrase inhibitors (D) act on the enzyme carbonic anhydrase in the proximal convoluted tubule and not directly on the NaCl cotransporter.

Correct Answer: D

Rationale: Carbapenems are broad-spectrum antibiotics that are effective against a wide range of both Gram-positive and Gram-negative microorganisms due to their strong activity against various types of bacteria. Option A is incorrect because carbapenems are not limited to only Gram-positive microorganisms. Option B is incorrect as they are effective against both Gram-positive and Gram-negative microorganisms. Option C is incorrect as carbapenems are not exclusively for bacteroide infections. The correct answer, Option D, is supported by the fact that carbapenems have a broad spectrum of activity against a wide range of bacteria.

Correct Answer: D

Rationale: The correct choice is D: Ciprofloxacin. Ciprofloxacin is a fluoroquinolone derivative known for its broad-spectrum antibacterial activity. It inhibits bacterial DNA gyrase and topoisomerase IV, essential enzymes for DNA replication. This mechanism leads to bacterial cell death. Chloramphenicol (A) inhibits bacterial protein synthesis, Nitrofurantoin (B) disrupts bacterial cell wall synthesis, and Nalidixic acid (C) inhibits bacterial DNA synthesis. Therefore, only Ciprofloxacin (D) targets DNA replication through gyrase inhibition, making it the correct choice.

Correct Answer: D

Rationale: The correct answer is D: Acyclovir. Acyclovir is the drug of choice for herpes and cytomegalovirus infections due to its specific antiviral activity against these viruses. It works by inhibiting viral DNA replication. Saquinavir is a protease inhibitor used for HIV, not herpes or cytomegalovirus. Interferon alfa is used for viral infections like hepatitis B and C, not herpes or cytomegalovirus. Didanozine is a nucleoside reverse transcriptase inhibitor used for HIV, not herpes or cytomegalovirus. Therefore, Acyclovir is the correct choice for these infections.