Red man syndrome has been associated with rapid intravenous injection of which of the following antibiotic?

Correct Answer: A

Rationale: The correct answer is A: Vancomycin. Red man syndrome is a type of hypersensitivity reaction associated with rapid intravenous infusion of vancomycin. This is due to the release of histamine from mast cells and basophils. Vancomycin is known to cause this syndrome, while the other antibiotics listed do not have a similar association. Clindamycin is more commonly associated with pseudomembranous colitis, Cefoperazone with liver toxicity, and Piperacillin with hypersensitivity reactions like rash or anaphylaxis. Therefore, based on the mechanism of action and clinical evidence, vancomycin is the correct choice for causing red man syndrome.

Correct Answer: D

Rationale: The correct answer is D: Clindamycin. Clindamycin is associated with the highest incidence of antibiotic-associated pseudomembranous enterocolitis due to its broad-spectrum activity that disrupts the normal gut flora, leading to overgrowth of Clostridium difficile. Ampicillin, Chloramphenicol, and Vancomycin are also associated with pseudomembranous enterocolitis, but the highest incidence is seen with Clindamycin due to its stronger impact on gut flora imbalance.

Correct Answer: B

Rationale: The correct answer is B. Nevirapine has a higher risk of severe hepatotoxicity in patients with higher CD4 cell counts. Choice B specifies a lower threshold for CD4 cell counts in women compared to men, which aligns with the caution needed for initiating Nevirapine. Choices A, C, and D have higher CD4 cell count thresholds for both women and men, which would increase the risk of hepatotoxicity if Nevirapine is initiated in those patients. Therefore, Choice B is the most appropriate option to minimize the risk of hepatotoxicity when initiating Nevirapine.

Correct Answer: B

Rationale: The correct answer is B: Ciprofloxacin. Ciprofloxacin is a fluoroquinolone antibiotic that interferes with DNA function in bacteria by inhibiting DNA gyrase and topoisomerase IV enzymes. This mechanism of action prevents bacterial DNA replication and repair, leading to bacterial cell death. Ciprofloxacin is effective in treating gonorrhea due to its ability to target and kill Neisseria gonorrhoeae, the bacteria causing gonorrhea. A: Chloramphenicol inhibits bacterial protein synthesis, not DNA function. C: Streptomycin disrupts bacterial protein synthesis by binding to the ribosome, not DNA function. D: Erythromycin inhibits bacterial protein synthesis by binding to the ribosome, not DNA function.

Correct Answer: zidovudine diphosphate

Rationale: The correct answer is D: Zidovudine is converted by cellular enzymes to an active form (zidovudine diphosphate). Zidovudine itself is a prodrug that needs to be metabolized by cellular enzymes to its active form, zidovudine diphosphate, which inhibits HIV replication by acting as a nucleoside reverse transcriptase inhibitor. This active form is essential for its antiretroviral activity. Incorrect Choices: A: Zidovudine in combination with other antiretrovirals is an alternative initial treatment for HIV infection - This is incorrect because zidovudine is commonly used in combination with other antiretrovirals as a first-line treatment for HIV infection, not as an alternative treatment. B: Zidovudine is also used to prevent transmission of HIV from the mother to her fetus and to treat AIDS-related dementia - This is incorrect because zidovudine is primarily used in