A 28 year old male patient present with a painless sore in his penis and blood * test confirms Treponema pallidum. Which of the following agent is the treatment of choice that can be given as a single dose?

Correct Answer: A

Rationale: The correct answer is A: Benzathine penicillin. The treatment of choice for syphilis caused by Treponema pallidum is penicillin. Benzathine penicillin is preferred due to its long-acting nature, providing sustained therapeutic levels. It is given as a single dose for early-stage syphilis. Ceftriaxone, vancomycin, and aztreonam are not effective against Treponema pallidum and are not recommended for the treatment of syphilis. Benzathine penicillin remains the first-line treatment due to its efficacy and established effectiveness against syphilis.

Correct Answer: C

Rationale: The correct answer is C: Interaction with the viral M2 protein. Amantadine blocks the M2 ion channel of the influenza A virus, preventing the release of viral RNA into the host cell. This inhibits the viral replication process. Option A is incorrect as amantadine does not target viral protease enzymes. Option B is incorrect as amantadine does not inhibit viral RNA-mediated DNA synthesis, which is a process specific to retroviruses. Option D is incorrect as amantadine does not interact with virus-directed thymidine kinase, which is involved in the activation of certain antiviral medications.

Correct Answer: B

Rationale: The correct answer is B: Nevirapine. Nevirapine is a non-nucleoside reverse transcriptase inhibitor (NNRTI) that directly inhibits HIV-reverse transcriptase without needing intracellular activation. It binds directly to the enzyme's active site, preventing the conversion of viral RNA to DNA. Rationale: 1. Nelnavir (A) is a protease inhibitor that works by blocking the protease enzyme needed for viral replication, not reverse transcriptase inhibition. 2. Stavudine (C) and Didanosine (D) are nucleoside reverse transcriptase inhibitors (NRTIs) that require intracellular phosphorylation to become active, unlike Nevirapine. In summary, Nevirapine is the correct answer as it directly inhibits HIV-reverse transcriptase without needing intracellular activation, distinguishing it from the other choices which belong to different drug classes or require intracellular phosphorylation.

Correct Answer: C

Rationale: Rationale for Correct Answer (C): 1. Zidovudine is a nucleoside reverse transcriptase inhibitor (NRTI) used in the treatment of HIV. 2. Zidovudine is indeed converted by cellular enzymes to its active form, zidovudine diphosphate. 3. Zidovudine diphosphate inhibits the reverse transcriptase enzyme, preventing viral DNA replication in HIV-infected cells. 4. This mechanism of action is crucial in reducing viral load and slowing disease progression in HIV patients. Summary of Incorrect Choices: A: Incorrect. While Zidovudine is used in combination therapy for HIV, it is not typically an alternative initial treatment. B: Incorrect. Zidovudine can be used to prevent mother-to-child transmission of HIV, but it is not its primary indication. D: Incorrect. Peripheral neuropathy is not a specific adverse reaction to Zidovudine; rather, it is more commonly associated with

Correct Answer: B

Rationale: The correct answer is B: Crotamiton. Crotamiton is not an antifungal drug; it is actually a scabicide and antipruritic agent used to treat scabies and itching. A: Tolnaftate is an antifungal commonly used to treat fungal skin infections like athlete's foot. C: Terbinafine is an antifungal medication used to treat fungal infections of the skin and nails. D: Ciclopirox is an antifungal used to treat fungal infections of the nails and skin.