Question

An HIV patient is on treatment with didanosine, stavudine, and indinavir. He is diagnosed to have pulmonary tuberculosis. Which one of the following ATT drugs is to be avoided?

• A. INH
• B. Rifampin
• C. PZA
• D. Ethambutol

Hint:

Rifampin strongly induces liver enzymes that break down protease inhibitors.

Answer 1

The Correct Option is B

Step 1: Note the patient's current ART regimen.
The patient is already on didanosine, stavudine, and indinavir. Indinavir belongs to the protease inhibitor class of antiretroviral drugs.

Step 2: Recall how protease inhibitors are broken down.
Protease inhibitors such as indinavir are metabolized in the liver mainly through the cytochrome P450 3A4 (CYP3A4) enzyme system. Anything that strongly induces this enzyme speeds up the breakdown of indinavir and lowers its blood level.

Step 3: Look at the standard anti-tubercular therapy (ATT) drugs.
INH (isoniazid) is a mild enzyme inhibitor and is generally safe to combine with protease inhibitors.
Rifampin is a very strong inducer of CYP3A4 and related liver enzymes. Giving rifampin along with indinavir causes a large drop in indinavir blood levels, enough to make the antiretroviral drug ineffective and to risk treatment failure and drug resistance.
Pyrazinamide (PZA) does not have this strong CYP3A4 induction effect and is usually continued.
Ethambutol is also not a significant enzyme inducer and can be safely continued.

Step 4: Decide the practical solution.
Because rifampin lowers protease inhibitor levels so strongly, standard practice is to either replace rifampin with rifabutin, which has much weaker enzyme induction, or adjust the antiretroviral regimen if rifampin absolutely must be used. In a patient already established on indinavir, avoiding rifampin is the safer path.

Final Answer:
Rifampin should be avoided in this patient because it drastically lowers indinavir levels through strong enzyme induction. \[ \boxed{\text{Rifampin}} \]