Case 2: Antiretrovirals and Tuberculosis Therapy

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Case last updated: June 30, 2004

A 37-year-old Hispanic male is newly diagnosed with both HIV infection and pulmonary tuberculosis. His laboratory studies show a CD4 count of 6 cells/mm3 and an HIV RNA greater than 500,000 copies/ml. He is started on four-drug therapy for tuberculosis that consists of isoniazid, ethambutol, rifampin, and pyrazinamide. The plan is to start antiretroviral therapy after one month of anti-tuberculosis therapy. One of two antiretroviral therapy regimens are being considered: (1) zidovudine plus lamivudine (Combivir) plus efavirenz (Sustiva), or (2) zidovudine plus lamivudine (Combivir) plus lopinavir-ritonavir (Kaletra).

Which of the following is true regarding a potential drug-drug interaction?

	Isoniazid will markedly decrease lopinavir and ritonavir levels.
	Rifampin will increase efavirenz levels by at least 50%.
	Rifampin can significantly lower lopinavir and ritonavir levels.
	Ethambutol will lower efavirenz levels by at least 50%.