This antitubercular drug has penetration to the CSF equal to plasma concentration, of which it is highly useful in meningeal TB:

Correct Answer: D

Rationale: Step-by-step rationale: 1. Pyrazinamide has excellent penetration into CSF due to its small molecular size and lipid solubility. 2. This characteristic makes it highly effective in treating meningeal tuberculosis. 3. Isoniazid, Rifampicin, and Ethambutol do not have the same level of CSF penetration as Pyrazinamide. 4. Isoniazid is primarily metabolized in the liver, Rifampicin has poor CSF penetration, and Ethambutol has limited penetration. 5. Therefore, Pyrazinamide is the most suitable choice for treating meningeal TB due to its ability to reach therapeutic concentrations in the CSF. Summary of incorrect choices: A. Isoniazid is metabolized in the liver and does not have equal penetration to CSF. B. Rifampicin has poor penetration into CSF compared to Pyrazinamide. C. Ethambutol has limited penetration to CS

Correct Answer: A

Rationale: The correct answer is A: Benzathine penicillin. Benzathine penicillin is the treatment of choice for syphilis caused by Treponema pallidum. It is given as a single dose due to its long-acting nature, ensuring adequate treatment. Ceftriaxone (B) is not the first-line treatment for syphilis. Vancomycin (C) is not effective against Treponema pallidum. Aztreonam (D) is not used for the treatment of syphilis. Therefore, the most appropriate choice for this scenario is Benzathine penicillin.

Correct Answer: A

Rationale: The correct answer is A: Nausea and vomiting. Ampicillin is a penicillin antibiotic that commonly causes gastrointestinal side effects such as nausea and vomiting due to its irritation of the stomach lining. This is the most frequent side effect reported with oral ampicillin use. Choices B (Loose bowel movements) and C (Constipation) are less common side effects associated with ampicillin use. Choice D (Urticaria) is a possible side effect of ampicillin, but it is less frequent compared to nausea and vomiting.

Correct Answer: C

Rationale: The correct answer is C because amantadine exerts its antiviral action by interacting with the viral M2 protein. This protein is essential for viral replication by facilitating the release of viral genetic material into the host cell. By binding to the M2 protein, amantadine disrupts this process, preventing viral replication. Choice A is incorrect because amantadine does not inhibit viral protease enzyme activity. Choice B is incorrect because amantadine does not target viral RNA mediated DNA synthesis. Choice D is incorrect because amantadine does not interact with a virus-directed thymidine kinase, which is involved in the activation of certain antiviral drugs like acyclovir.

Correct Answer: B

Rationale: The correct answer is B: Nevirapine. Nevirapine is a non-nucleoside reverse transcriptase inhibitor (NNRTI) that directly inhibits the HIV-reverse transcriptase enzyme without the need for intracellular activation by phosphorylation. It binds to a hydrophobic pocket near the enzyme's active site, thus preventing viral RNA from being converted to DNA. A: Nelfinavir is a protease inhibitor that works by blocking the activity of the protease enzyme, not directly inhibiting reverse transcriptase. C: Stavudine and D: Didanosine are nucleoside reverse transcriptase inhibitors (NRTIs) that require intracellular phosphorylation to become active and inhibit reverse transcriptase.