Moderate. These medicines may cause some risk when taken together. Contact your healthcare professional (e.g. doctor or pharmacist) for more information.
How the interaction occurs:
Efavirenz may speed up how quickly your liver processes rifabutin.
What might happen:
The amount of rifabutin in your blood may decrease and it may not work as well against your infection.
What you should do about this interaction:
Let your healthcare professionals (e.g. doctor or pharmacist) know that you are taking these medicines together. Your doctor may want to change the dose of your medicine.Your healthcare professionals may already be aware of this interaction and may be monitoring you for it. Do not start, stop, or change the dosage of any medicine before checking with them first.
1.Sustiva (efavirenz) US prescribing information. Bristol-Myers Squibb Company March, 2016.
2.Atripla (efavirenz/emtricitabine/tenofovir disoproxil fumarate) US prescribing information. Gilead Sciences, Inc. February, 2016.
3.Weiner M, Benator D, Peloquin CA, Burman W, Vernon A, Engle M, Khan A, Zhao Z. Evaluation of the drug interaction between rifabutin and efavirenz in patients with HIV infection and tuberculosis. Clin Infect Dis 2005 Nov 1;41(9):1343-9.
4.Hsu O, Hill CJ, Kim M, Tan B, O'Brien JG. Decreased plasma efavirenz concentrations in a patient receiving rifabutin. Am J Health Syst Pharm 2010 Oct 1;67(19):1611-4.
5.Edelstein HE, Cuadros Y. Failure of treatment of tuberculous adenitis due to an unexpected drug interaction with rifabutin and efavirenz. AIDS 2004 Aug 20;18(12):1748-9.