This drug binds bile acids in the GI tract:

Correct Answer: A

Rationale: Rationale: Cholestyramine binds bile acids in the GI tract, preventing their reabsorption and promoting excretion. This helps lower cholesterol levels. Nicotinic acid, gemfibrozil, and probucol work through different mechanisms and are not bile acid binders. Nicotinic acid lowers LDL and triglycerides, gemfibrozil decreases triglycerides, and probucol increases HDL. Therefore, the correct answer is A.

Correct Answer: C

Rationale: The correct answer is C: Potassium-sparing diuretics. Potassium-sparing diuretics act in the collecting tubules by blocking the sodium-potassium exchange, leading to decreased sodium reabsorption and potassium retention. This mechanism helps to promote diuresis while preventing potassium loss. Loop diuretics (A) act in the loop of Henle, thiazide diuretics (B) act in the distal convoluted tubule, and carbonic anhydrase inhibitors (D) act in the proximal convoluted tubule. Therefore, they are not directly involved in the collecting tubules like potassium-sparing diuretics.

Correct Answer: D

Rationale: The correct answer is D (All of the above) because all three choices (Clavulanic acid, Sulbactam, Tazobactam) are beta-lactamase inhibitors commonly co-administered with penicillins to enhance their efficacy. Beta-lactamase inhibitors work by inhibiting bacterial enzymes that can inactivate penicillins, allowing the antibiotic to remain effective against the bacteria. Clavulanic acid, Sulbactam, and Tazobactam are specifically designed to counteract beta-lactamase enzymes produced by bacteria, making them effective choices for combination therapy with penicillins. The other choices (A, B, C) are incorrect as each of them alone is a valid beta-lactamase inhibitor used in clinical practice.

Correct Answer: B

Rationale: The correct answer is B: Metronidazole. Metronidazole is a nitroimidazole derivative commonly used as an antibacterial and antiprotozoal drug. It works by disrupting the DNA structure of bacteria and parasites, leading to their death. Clavulanic acid (A) is a beta-lactamase inhibitor, not an antibacterial drug. Nitrofurantoin (C) is a nitrofuran derivative used for urinary tract infections, not a nitroimidazole derivative. Doxycycline (D) is a tetracycline antibiotic, not a nitroimidazole derivative. Therefore, the correct choice is B as it is the only nitroimidazole derivative among the options provided.

Correct Answer: A

Rationale: The correct answer is A: Zidovudine. Zidovudine is a nucleoside reverse transcriptase inhibitor that works by inhibiting the viral reverse transcriptase enzyme, essential for viral replication in HIV-infected cells. This action helps to slow down the progression of HIV infection. Vidarabine is an antiviral drug used to treat herpes simplex and varicella-zoster viruses, not HIV. Rimantadine is an antiviral drug used to treat and prevent influenza A virus infections by inhibiting viral replication, but it does not inhibit viral reverse transcriptase. Gancyclovir is an antiviral drug used to treat cytomegalovirus infections by inhibiting viral DNA polymerase, not reverse transcriptase.