Which of the following antivitamins prevent a vitamin K from exerting its typical metabolic effects?

Correct Answer: D

Rationale: The correct answer is D - All of the above. Cholestyramine binds bile acids, leading to malabsorption of fat-soluble vitamins like vitamin K. Coumarins inhibit the recycling of vitamin K epoxide, reducing its availability. Certain antibiotics disrupt gut flora, affecting vitamin K production. Therefore, all choices prevent vitamin K from exerting its metabolic effects.

Correct Answer: D

Rationale: The correct answer is D because cholecalciferol, also known as vitamin D3, exerts its effects through genomic effects (regulating gene expression) and cytoplasmic effects (regulating calcium transport). This is crucial for its role in calcium homeostasis and bone health. A is incorrect because cholecalciferol is typically administered orally and does not require frequent monitoring of calcium and phosphorus serum levels. B is incorrect because cholecalciferol promotes bone formation by enhancing osteoblast activity, not inhibiting osteoclasts. C is incorrect because cholecalciferol actually helps increase serum calcium levels by enhancing calcium absorption in the intestines and promoting calcium reabsorption in the kidneys, rather than lowering them.

Correct Answer: C

Rationale: Sustained use of furosemide and acetazolamide can lead to increased plasma urate concentrations. Furosemide inhibits uric acid secretion, while acetazolamide impairs renal excretion of uric acid. Therefore, both drugs can result in elevated plasma urate levels. Choice C is correct. Choice A is incorrect because furosemide does not decrease plasma urate concentrations. Choice B is incorrect because acetazolamide does not lower plasma urate concentrations. Choice D is incorrect as both drugs can increase plasma urate levels.

Correct Answer: C

Rationale: The correct answer is C: Clindamycin. Clindamycin is not an aminoglycoside; it belongs to the lincosamide class. Gentamicin, Streptomycin, and Neomycin are aminoglycosides. Aminoglycosides are characterized by their mechanism of action involving binding to the bacterial ribosome, leading to inhibition of protein synthesis. Clindamycin, on the other hand, acts by inhibiting bacterial protein synthesis at a different site. Therefore, Clindamycin does not belong to the aminoglycoside group.

Correct Answer: B

Rationale: The correct answer is B: Inhibition of DNA dependent RNA polymerase. Rifampin selectively inhibits bacterial RNA polymerase, specifically the DNA-dependent RNA polymerase, leading to the suppression of RNA synthesis. This disrupts bacterial protein production, ultimately causing bacterial cell death. Incorrect answers: A: Inhibition of mycolic acids synthesis - Rifampin does not target mycolic acid synthesis, which is specific to mycobacteria. C: Inhibition of topoisomerase II - Rifampin does not target topoisomerase II, which is involved in DNA replication and repair. D: Inhibition of cAMP synthesis - Rifampin does not inhibit cAMP synthesis, which is a signaling molecule involved in various cellular processes.