A 20 year old patient presented to the ER with headache, stiff neck and fever for 3 days and is diagnosed with bacterial meningitis. Which one of the following antibiotics is the best choice to treat meningitis?

Correct Answer: C

Rationale: The correct answer is Cefotaxime (C) because it is a third-generation cephalosporin with excellent penetration into the cerebrospinal fluid, making it effective against bacterial meningitis pathogens. Cefotaxime covers a broad spectrum of bacteria commonly causing meningitis, including Streptococcus pneumoniae and Neisseria meningitidis. A: Cefuroxime (A) is not the best choice as it has limited activity against some of the common pathogens causing meningitis. B: Cephalexin (B) is a first-generation cephalosporin with poor central nervous system penetration and limited activity against meningitis pathogens. D: Cefdinir (D) is a third-generation cephalosporin but is not the preferred choice for treating bacterial meningitis due to its inferior CNS penetration compared to cefotaxime.

Correct Answer: C

Rationale: The correct answer is C: Primaquine. Primaquine is used for clinical curative treatment of malaria, particularly for the eradication of hypnozoites in Plasmodium vivax and Plasmodium ovale infections. It is not used as a prophylactic drug due to its potential side effects, such as hemolysis in individuals with G6PD deficiency. Choice A (Pyrimethamine + sulfadoxine) is a combination used for both treatment and prophylaxis. Choice B (Proguanil) is used for prophylaxis and treatment. Choice D (Mefloquine) is used for both prophylaxis and treatment of malaria.

Correct Answer: C

Rationale: The correct answer is C: Amantadine. Amantadine is an antiviral medication that is specifically effective against influenza A virus. It works by blocking the viral ion channel, preventing the virus from entering the host cell. This inhibits viral replication and helps reduce the severity and duration of symptoms. Choice A, Cidofovir, is used to treat certain DNA viruses but is not effective against influenza A. Choice B, Famciclovir, is used to treat herpes viruses, not influenza A. Choice D, Ribavirin, is an antiviral medication used for respiratory syncytial virus and hepatitis C, but not as effective against influenza A. Therefore, the most appropriate choice in this scenario is Amantadine due to its specific activity against influenza A virus.

Correct Answer: D

Rationale: Rationale for choice D: Retroviral protease inhibitors, such as lopinavir and ritonavir, are correct because they are more active in inhibiting HIV replication than zidovudine (B) and they inhibit CYP 3A4 and interact with many other drugs (C). Explanation for why other choices are incorrect: A: Retroviral protease inhibitors do not act at an early step in HIV replication; they act by blocking the protease enzyme necessary for viral maturation. B: Zidovudine is a nucleoside reverse transcriptase inhibitor, not a protease inhibitor, so retroviral protease inhibitors are more potent against HIV. C: While retroviral protease inhibitors do inhibit CYP 3A4 and interact with other drugs, this statement alone does not capture the complete picture of their mechanism of action or potency compared to zidovudine.

Correct Answer: D

Rationale: The correct answer is D: Piperazine. Piperazine is a paralytic agent that causes relaxation of the muscles of the roundworm (Ascaris), allowing it to be easily expelled from the intestine. By administering piperazine via orogastric tube, the clumped roundworms causing intestinal obstruction can be relaxed, relieving the obstruction. Levamisole, Mebendazole, and Pyrantel pamoate are not effective in relaxing the muscles of the roundworms, making them incorrect choices for this specific scenario.