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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.



Over 21 days, EE levels among the efavirenz groups were 53%-57% lower than those of controls. Levels among the atazanavir groups were 29%-59% lower.

On days 7, 14, and 21, the EE geometric means ratios in efavirenz-treated patients versus controls were 0.47, 0.45, and 0.43, respectively (P less than .05 for each comparison).

In the atazanavir group, the EE geometric mean ratios versus controls at the same time points were 0.68 (P nonsignificant), 0.71 (P less than .05), and 0.65 (P less than .05).

For those in the efavirenz group, etonogestrel levels over 21 days were 76%-79% lower than in controls. In contrast, levels in the atazanavir group were 71%-79% higher than in controls.

The geometric mean ratios for the efavirenz group at 7, 14, and 21 days versus controls were 0.21, 0.22, and 0.24 (P less than .05 for all comparisons). In the atazanavir group, the respective geometric mean ratios were 1.71, 1.79, and 1.74 (P less than .05 for all comparisons).

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