Which of the following fungicidal drug that acts by inhibiting fungal squalene epoxidase enzyme and is the drug of choice for onychomycosis of the toe nails in 56 year old woman with diabetes?

Correct Answer: B

Rationale: Step 1: Terbinafine is a fungicidal drug that inhibits fungal squalene epoxidase enzyme, disrupting fungal cell membrane synthesis. Step 2: Onychomycosis of toenails is a common fungal infection that terbinafine is specifically effective against. Step 3: The patient being a 56-year-old woman with diabetes may require a drug with good efficacy and safety profile, making terbinafine an appropriate choice. Step 4: Griseofulvin (A) works by disrupting microtubule function, not inhibiting squalene epoxidase. Itraconazole (C) is an azole antifungal that inhibits ergosterol synthesis, not squalene epoxidase. Amphotericin B (D) is a polyene antifungal used for systemic mycoses, not onychomycosis.

Correct Answer: D

Rationale: Rationale: 1. Ritonavir is a protease inhibitor used in HIV treatment. 2. It works by inhibiting the HIV protease enzyme, preventing viral replication. 3. Lamivudine, Efavirenz, and Stavudine are not protease inhibitors but work through different mechanisms. 4. Lamivudine is a nucleoside reverse transcriptase inhibitor, Efavirenz is a non-nucleoside reverse transcriptase inhibitor, and Stavudine is another nucleoside reverse transcriptase inhibitor. Summary: Ritonavir is the correct answer as it directly targets the HIV protease enzyme, unlike the other options which act on reverse transcriptase enzymes.

Correct Answer: B

Rationale: The correct answer is B: Azithromycin. It is preferred for short-term treatment due to its long half-life allowing once-daily dosing. Azithromycin has a broad spectrum of activity against many pathogens causing ENT, respiratory, and genital infections. It is well-tolerated and has fewer drug interactions. Other choices like A: Erythromycin have a higher frequency of dosing and more side effects. C: Clarithromycin and D: Roxithromycin are not typically given once daily for 3 days.

Correct Answer: A

Rationale: The correct answer is A: Nifurtimox. Nifurtimox is the first-line treatment for Chagas disease caused by Trypanosoma cruzi. It is effective in treating both acute and chronic phases of the disease by reducing parasitemia. Metronidazole (B) is used for anaerobic bacterial infections, not trypanosomiasis. Suramin (C) is used for African trypanosomiasis, not American trypanosomiasis. Chloroquine (D) is used for malaria, not trypanosomiasis. Therefore, A is the most appropriate choice for this patient.

Correct Answer: B

Rationale: The main reason for using combination therapy in TB treatment is to delay or prevent the emergence of resistance. Step 1: TB is caused by Mycobacterium tuberculosis, which has a high mutation rate leading to drug resistance. Step 2: With combination therapy, multiple drugs target different aspects of the bacteria's lifecycle, making it harder for resistance to develop. Step 3: This approach ensures that if one drug becomes ineffective due to resistance, others can still be effective. Summary: Choice B is correct as it directly addresses the issue of resistance, which is a critical concern in TB treatment. Choices A, C, and D are incorrect because reducing side effects, increasing antimycobacterial activity, and providing prophylaxis against other bacterial infections are not the primary reasons for using combination therapy in TB.