Pharmacokinetic interaction between nevirapine and ethinyl estradiol/norethindrone when administered concurrently to HIV-infected women.

OBJECTIVE: To determine the effects of nevirapine (NVP), a nonnucleoside reverse-transcriptase inhibitor of HIV-1 and P450 inducer, on the pharmacokinetics (PK) of ethinyl estradiol (EE)/norethindrone (NET), a widely used oral contraceptive, and to assess the effects of EE/NET on the steady-state PK of NVP.
METHODS: Ten HIV-1-infected women underwent intensive PK sampling after single-dose administration of EE/NET (days 0-1). Oral NVP 200 mg once daily (days 2-15), followed by 200 mg twice daily (days 16-29), was added to background potent antiretroviral therapy. On day 30, intensive PK sampling was performed after concurrent administration of NVP 200 mg and a single dose of EE/NET.
RESULTS: Concomitant administration of NVP at steady state with EE/NET resulted in a significant (29%) median reduction in the area under the plasma concentration time curve (AUC(infinity)) and a significant reduction in mean residence time (MRT) and half-life (t(1/2)) of EE. There was a significant (18%) median reduction in the AUC(infinity) for NET that was not associated with a detectable change in NET C(max), MRT, or t(1/2).
CONCLUSION: Oral contraceptives should not be the primary method of birth control in women of child-bearing potential who are treated with NVP.