Antitubercular drug which should not be given to a patient having both tuberculosis as well as AIDS is :
First, the core concept here is drug interactions between antitubercular medications and antiretroviral drugs used in HIV/AIDS. Specifically, the question is asking which drug should be avoided in a patient co-infected with TB and HIV.
Common antitubercular drugs include isoniazid, rifampin, rifabutin, pyrazinamide, ethambutol, and streptomycin. Now, rifampin is a known inducer of hepatic enzymes, especially CYP3A4. This can lead to decreased levels of protease inhibitors and some non-nucleoside reverse transcriptase inhibitors (NNRTIs) used in HIV treatment, making them less effective. However, in HIV-TB co-infected patients, the standard of care often involves using rifamycin derivatives like rifabutin instead of rifampin because rifabutin has a lower risk of interacting with antiretroviral drugs, particularly protease inhibitors. Wait, but maybe the correct answer is rifampin because it's the one that should be avoided due to these interactions. Let me double-check.
If the options included rifampin, then that's the answer. But if the options are between rifampin and rifabutin, then rifampin is the one to avoid. Another possibility is ethambutol, but I don't think it interacts with antiretrovirals. Isoniazid might interact with some drugs but not as significantly as rifampin. Pyrazinamide is generally safe in this context.
So the correct answer is likely rifampin. The clinical pearl here is that rifampin should be avoided in HIV-TB co-infection due to its enzyme-inducing properties, which reduce the efficacy of antiretroviral drugs. Instead, rifabutin is preferred when a rifamycin is needed. That makes sense. Therefore, the answer is rifampin.
**Core Concept**
This question tests knowledge of drug interactions between antitubercular medications and antiretroviral therapy (ART) in HIV/TB co-infection. **Rifampin**, a potent **CYP3A4 inducer**, reduces plasma concentrations of **protease inhibitors (PIs)** and **non-nucleoside reverse transcriptase inhibitors (NNRTIs)**, compromising ART efficacy.
**Why the Correct Answer is Right**
**Rifampin** induces hepatic cytochrome P450 enzymes (**CYP3A4**), accelerating the metabolism of **lopinavir/ritonavir** and **efavirenz**, leading to subtherapeutic ART levels. This interaction increases HIV viral load and treatment failure risk. Guidelines recommend **rifabutin** (a weaker inducer) as the preferred rifamycin in HIV/TB co-infection.
**Why Each Wrong Option is Incorrect**
**Option A: Isoniazid** – Does not significantly interact with ART and is safe in co-infection.
**Option B: Pyrazinamide