Conference Coverage

Efavirenz-based ART may hamper vaginal ring contraception


Key clinical point: Some anti-HIV agents may interfere with the efficacy of hormone-based contraceptives.

Major finding: Estrogen exposure in women on efavirenz was 53%-57% lower than among controls.

Study details: A pharmacokinetic study in 74 HIV-infected women.

Disclosures: The study was supported by the National Institutes of Health. Merck provided the vaginal ring used in the study. Dr. Scarsi reported having no conflicts of interest to disclose.

Source: Scarsi KK et al. CROI 2018, Abstract 141.



She noted that the findings have important implications for developers of vaginal rings designed to prevent HIV transmission as well as provide hormone-based contraception.

Dr. Scarsi and colleagues conducted a phase 2, international, nonrandomized, parallel pharmacokinetic study comparing levels of estrogen in the form of ethinyl estradiol (EE) and progestin in the form of etonogestrel among women with HIV infection who had not yet begun ART, as well as women on efavirenz- or atazanavir-based regimens.

Participants 16 years and older from centers in Africa, Asia, and North and South America were enrolled. The patients had to be willing to use a second, nonhormonal form of effective contraceptive, and if they were not on ART had to have CD4 cell counts of 350 cells/m3 or higher at screening. Participants on ART had to be on stable therapy for at least 30 days, and have HIV-1 RNA of 400 copies/mL or less.

A total of 25 control subjects, 25 women on efavirenz, and 24 on atazanavir were available for the primary pharmacokinetic analysis.

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