The drug is a potassium-sparing diuretic that blocks Na+ channels in the collecting tubules:

Correct Answer: B

Rationale: The correct answer is B: Amiloride (Midamor). It is a potassium-sparing diuretic that blocks Na+ channels in the collecting tubules. Amiloride specifically targets the epithelial sodium channels in the collecting tubules, leading to decreased sodium reabsorption and potassium retention. Acetazolamide (A) is a carbonic anhydrase inhibitor, Furosemide (C) is a loop diuretic that inhibits the Na+-K+-2Cl- symporter, and Hydrochlorothiazide (D) is a thiazide diuretic that inhibits the Na+-Cl- symporter in the distal convoluted tubule.

Correct Answer: D

Rationale: The correct answer is D: Rifampin. Rifampin is an antimycobacterial drug that is commonly used to treat tuberculosis and other mycobacterial infections. It works by inhibiting the RNA polymerase enzyme in mycobacteria, leading to the suppression of bacterial growth. Isoniazid (Choice A) is also used for tuberculosis treatment, but it is not classified as an antibiotic. PAS (Choice B) is an antimycobacterial drug but is not an antibiotic. Ethambutol (Choice C) is also used to treat tuberculosis, but it works by inhibiting cell wall synthesis rather than RNA polymerase. Therefore, the correct choice is Rifampin as it directly targets the mycobacterial RNA polymerase enzyme, making it an effective antibiotic for treating mycobacterial infections.

Correct Answer: A

Rationale: Niclosamide inhibits oxidative phosphorylation by blocking the electron transport chain in helminthes. It disrupts their energy production, leading to paralysis and death. Piperazine acts on GABA receptors, Praziquantel disrupts the parasite's tegument, and Mebendazole inhibits microtubule function. Therefore, Niclosamide is the correct choice for inhibiting oxidative phosphorylation in helminthes.

Correct Answer: A

Rationale: Flutamide is the correct answer as it is a known antiandrogen drug used to treat conditions like prostate cancer. It works by blocking the action of androgens in the body. Aminoglutethimide is not an antiandrogen but an aromatase inhibitor. Tamoxifen is a selective estrogen receptor modulator used in breast cancer treatment. Testosterone is a natural male hormone and not an antiandrogen. Therefore, Flutamide is the correct choice for an antiandrogen drug.

Correct Answer: B

Rationale: The correct answer is B: Niacin. Niacin can cause hepatotoxicity and exacerbate liver conditions, which would be a concern in this patient. Cholestyramine (A) works in the intestines, Ezetimibe (C) inhibits cholesterol absorption, and Lovastatin (D) inhibits cholesterol synthesis in the liver, none of which are contraindicated in liver conditions.