The antiviral action of amantadine is exerted through:

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: 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.

Correct Answer: B

Rationale: Step-by-step rationale for why Pyrantel pamoate (choice B) is the correct answer: 1. Pyrantel pamoate is a cholinergic agonist that acts on nematodes by stimulating nicotinic receptors, leading to spastic paralysis of the worms. 2. Its mechanism of action involves depolarizing the neuromuscular junction, causing sustained muscle contraction in the parasites. 3. This spastic paralysis makes the worms lose their ability to maintain attachment to the host's intestine, facilitating their expulsion from the body. 4. Piperazine (choice A) works by blocking the response of the worm's muscle cells to acetylcholine, causing flaccid paralysis. 5. Mebendazole (choice C) and Albendazole (choice D) are benzimidazole anthelmintics that inhibit microtubule formation, leading to impaired glucose uptake and energy depletion in the parasites, not acting as cholinergic agonists.

Correct Answer: C

Rationale: The correct answer is C: Clofazimine. Clofazimine is an antileprosy drug that is known to suppress both lepra reactions and reversal reactions. It has anti-inflammatory properties that help control and prevent leprosy reactions. Dapsone (A) is primarily used for leprosy treatment but does not specifically target lepra and reversal reactions. Rifampin (B) is effective against the leprosy bacteria but is not known for its role in managing lepra reactions. Minocycline (D) is another antibiotic used in leprosy treatment but does not have the same anti-inflammatory properties as clofazimine. Therefore, clofazimine is the correct choice for managing both lepra and reversal reactions in leprosy patients.

Correct Answer: B

Rationale: The correct answer is B: Testosterone. Dutasteride is a 5-alpha reductase inhibitor used to treat BPH by reducing DHT levels. Testosterone is converted to DHT by the enzyme 5-alpha reductase, so combining dutasteride with testosterone can potentially increase the risk of side effects related to low DHT levels. Tamsulosin is an alpha blocker and does not directly interact with dutasteride. Sildenafil is a phosphodiesterase inhibitor used for erectile dysfunction and does not have a known interaction with dutasteride. Hydrochlorothiazide is a diuretic and is unlikely to interact with dutasteride.