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Home > Treatment > HIV Meds Quarterly > Fall 2008 > Atazanavir
Atazanavir: Interactions with Efavirenz, Nevirapine, and Oral Hormonal Contraceptives

The atazanavir product label has been updated to include new information on several important drug interactions.

Efavirenz: Efavirenz is known to decrease atazanavir levels substantially. In order to offset this interaction, previous recommendations indicated that atazanavir 300 mg should be combined with ritonavir 100 mg once daily. The manufacturer now recommends a higher atazanavir dosage for ARV-naive patients who take efavirenz: atazanavir 400 mg once daily + ritonavir 100 mg once daily. For treatment-experienced patients, the manufacturer warns that atazanavir should not be coadministered with efavirenz.
Nevirapine: Two-way interactions between atazanavir and nevirapine cause decreases in serum atazanavir levels and increases in nevirapine levels. The manufacturer warns that these drugs should not be used in combination.
Oral hormonal contraceptives: Atazanavir, like most protease inhibitors, interacts significantly with both ethinyl estradiol (EE) and norethindrone (NE). Unboosted atazanavir increases serum EE levels, and increases the risk of EE adverse effects. Ritonavir-boosted atazanavir decreases serum EE levels, and increases the risk of contraceptive failure. Atazanavir, whether combined with ritonavir or not, also increases NE levels, risking NE adverse effects.

The atazanavir package label provides recommendations for dosage of EE in patients taking atazanavir, but few efficacy or safety data on the use of hormonal contraceptives with atazanavir or other protease inhibitors are available; alternative methods of contraception should be considered. If oral hormonal contraceptives are given to women who take atazanavir, the efficacy and safety of the contraceptive should be monitored carefully. Few data regarding the effects of atazanavir with other, non-oral hormonal contraceptives are available.

For further information on atazanavir drug interactions, see the atazanavir product label or the HIV InSite Database of Antiretroviral Drug Interactions.