A 35 year old man heroin addict on methadone maintenance therapy for the last one year, is positive for TB on Chest x-ray. He was started on standard quadri anti-TB drug. He is rushed to ER complaining of withdrawal symptoms. Which of the following anti-TB drugs is likely to cause this patient’s withdrawal reaction?

Correct Answer: B

Rationale: The correct answer is B: Rifampicin. Rifampicin is known to induce cytochrome P450 enzymes, leading to increased metabolism of methadone and subsequently causing withdrawal symptoms in methadone-maintained patients. Streptomycin (A) is an aminoglycoside antibiotic used in TB treatment but does not interact with methadone. INH (C) and Pyrazinamide (D) do not have significant interactions with methadone metabolism. Therefore, Rifampicin is the likely cause of this patient's withdrawal symptoms.

Correct Answer: C

Rationale: The correct answer is C because Steven-Johnson syndrome is a severe and life-threatening skin reaction that can occur with certain medications like Trimethoprim/Sulfamethoxazole. Once a patient experiences this reaction, they should never be given the same drug again to avoid a potentially fatal outcome. The other choices, GI upset from Clarithromycin, skin rash from Ampicillin, and Clostridium difficile superinfection from Ofloxacin, are adverse reactions that can be managed or treated without completely excluding the drug from future use.

Correct Answer: A

Rationale: Cloxacillin is a beta-lactam antibiotic effective against Staphylococci. Staphylococci commonly cause skin and soft tissue infections. Streptococci are not typically treated with cloxacillin. Gonococci are not susceptible to cloxacillin. Therefore, the correct answer is A, as it is the only organism listed that is indicated for treatment with cloxacillin.

Correct Answer: C

Rationale: The correct answer is C: Trimethoprim/Sulfamethoxazole. This combination is the first-line treatment for Pneumocystis carinii pneumonia in patients with HIV-AIDS due to its efficacy against the organism. Trimethoprim inhibits dihydrofolate reductase, while sulfamethoxazole inhibits dihydropteroate synthase, both essential enzymes for folate synthesis in bacteria and protozoa like P. carinii. Metronidazole (A) is used for anaerobic infections, Carbenicillin (B) is a penicillinase-resistant penicillin used for Gram-negative infections, and Penicillin G (D) is a narrow-spectrum antibiotic mainly used for Gram-positive infections.

Correct Answer: A

Rationale: The correct answer is A: Two nucleoside reverse transcriptase inhibitors (NRTIs) + one protease inhibitor (PI). This regimen is typically reserved for advanced cases of AIDS or repeated treatment failures due to its high potency and effectiveness in suppressing HIV replication. NRTIs work by blocking the reverse transcriptase enzyme, while PIs inhibit the protease enzyme, both essential for HIV replication. Combining two NRTIs with a PI targets the virus at multiple stages, reducing the likelihood of resistance development. In contrast, the other choices (B, C, D) do not offer the same level of efficacy or resistance prevention as the combination in choice A. B: Three NRTIs may lead to increased toxicity without added benefit. C: Two NRTIs + one non-NRTI lacks the potency of a PI in advanced cases. D: One NRTI + one non-NRTI + one PI is not as effective as two NRTIs + one PI in suppressing