Atazanavir causes a decrease in concentration of Ethinyl Estradiol in women using vaginal hormonal contraceptives. Precaution should be taken when using hormonal vaginal contraceptives when on Protease Inhibitors. Alternative contraceptive methods should be considered.
Atazanavir/Ritonavir versus Ethinyl Estradiol
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Study Design
A vaginal ring releasing Etonogestrel/Ethinyl Estradiol (ENG/EE) 120/15 mcg/day was inserted at entry in three groups of participants: (1) not yet receiving ART (control group; n=25); (2) ART containing efavirenz EFV 600mg daily (EFV group; n=25); (3) ART containing atazanavir/ritonavir ATV/r 300/100mg daily (ATV/r group; n=24). Participants returned on days 7, 14, and 21 for single measurements of ENG and EE PK, assessed by a validated LC/MS/MS method. Plasma hormone PK exposure was compared between each ART group and the control group at each visit by geometric mean ratio (GMR) with 90% CI, and by Wilcoxon-rank sum at the primary endpoint (day 21).
Study Results
Compared to the control group, participants in the EFV group had 76-79% lower ENG and 53-57% lower EE over 21 days (all p<0.001). In contrast, participants in the ATV/r group had 71-79% higher ENG (all p<0.001), yet 29-35% lower EE (p=0.066, 0.032 and 0.004 for days 7, 14 and 21, respectively) over 21 days compared to the control group. The GMR (90% CI) for ENG and EE concentrations for ATV: Control at Day 21 were 1.74 (1.38-2.20) and 0.65 (0.50-0.84) respectively.
Study Conclusions
Women on ATV/r-based ART should consider an alternative contraception method or barrier contraception in addition to the vaginal ring until the clinical relevance of these PK changes is better understood.
References
Scarsi, K, Cramer, S, Gingrich, D. Vaginal contraceptive hormone exposure profoundly altered by efv- and atv/r-based art. Conference On Retroviruses And Opportunistic Infections. Boston. 2018; March 2018.
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