Question | Discussion | References | CME Credit

Case 2: Antiretrovirals and Tuberculosis Therapy

You answered:

B Rifampin will increase efavirenz levels by at least 50%.

This answer is incorrect. In combination with rifampin, efavirenz levels are reduced (maximum concentration decreased by 20% and area under the curve [AUC] decreased by 22%). It may be possible to use efavirenz in combination with rifampin, but the clinical outcomes are unknown. Rifabutin is an alternative, since it does not significantly lower efavirenz levels. Because efavirenz lowers rifabutin levels, the rifabutin dose should be increased from 300 mg qd to 450 mg qd or 600 three times per week to compensate for the enzyme induction caused by efavirenz.

A Isoniazid will markedly decrease darunavir and ritonavir levels.
C Rifampin will significantly lower darunavir and ritonavir levels.
D Ethambutol will lower efavirenz levels by at least 50%.

[Back to Case 2 Question | Go to Correct Answer]