This class of drug exert its antimicrobial action by binding to 30S ribosomes and inhibit bacterial protein synthesis, is the drug of choice for treating non-gonococcal urethritis caused by Chlamydia and Ureaplasma, but should be avoided in patients with liver disease:

Correct Answer: D

Rationale: The correct answer is D: Tetracyclines. Tetracyclines work by binding to the 30S ribosomal subunit of bacteria, inhibiting protein synthesis. They are effective in treating non-gonococcal urethritis caused by Chlamydia and Ureaplasma. However, tetracyclines should be avoided in patients with liver disease due to the potential for hepatotoxicity. Explanation: 1. Daptomycin (A) is a lipopeptide antibiotic that acts by disrupting bacterial cell membrane function, not by binding to ribosomes. 2. Carbapenems (B) are beta-lactam antibiotics that inhibit bacterial cell wall synthesis, not protein synthesis via ribosomal binding. 3. Cephalosporins (C) are beta-lactam antibiotics that also inhibit cell wall synthesis and do not target ribosomes like tetracyclines do.

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.

Correct Answer: D

Rationale: The correct answer is D: Foscarnet. Foscarnet is a pyrophosphate analog that inhibits both DNA polymerase and reverse transcriptase, making it effective against cytomegalovirus (CMV) infection in AIDS patients. It is not a nucleoside analog like Acyclovir (A) and Valacyclovir (B) which target viral DNA polymerase. Amantadine (C) is an antiviral drug used for influenza A virus, not CMV. Foscarnet is specifically indicated for CMV infection in AIDS patients due to its unique mechanism of action, making it the correct choice.