Etonogestrel concentrations among contraceptive implant users in Botswana using and not using dolutegravir-based antiretroviral therapy

Objectives:

To evaluate whether etonogestrel concentrations are reduced to a level that could potentially reduce contraceptive efficacy when the etonogestrel contraceptive implant is used concomitantly with dolutegravir-based antiretroviral therapy (ART).

Study Design:

We conducted a non-randomized, open-label, cross-sectional pharmacokinetic study among women using single-rod etonogestrel contraceptive implants in Botswana. We compared plasma etonogestrel concentrations, sampled at a single time-point between 3 and 12 months from implant insertion, among implant users living with HIV and receiving dolutegravir-based ART with HIV-negative implant users. We also assessed concentrations among implant users living with HIV and receiving efavirenz-based ART. We compared geometric mean etonogestrel concentrations analyzing data from 142 participants: 97 HIV-negative, 30 using dolutegravir, and 15 using efavirenz.

Results:

The groups were similar. Duration of implant use was between 3 and 12 months (median=5). Geometric mean etonogestrel plasma concentrations and 90% confidence intervals of the mean were 227.5(212.4-243.8), 289.6(251.8-333.0) and 76.4(63.9-91.4) pg/mL among the HIV-negative, dolutegravir- and efavirenz-based ART groups, respectively. All women in the HIV-negative and dolutegravir-based ART groups had etonogestrel concentrations above 90pg/mL; 9/15 women (60%) using efavirenz-based ART had concentrations below 90 pg/mL. On average, etonogestrel levels were lower among individuals who had implants inserted for longer durations.

Conclusions:

Implant users receiving dolutegravir-based ART had a higher mean etonogestrel concentration compared to HIV-negative women, and none had etonogestrel concentrations below the posited threshold for ovulation suppression. In contrast, women in the efavirenz-group had much lower etonogestrel concentrations. Overall, these data provide evidence that the etonogestrel implant may be effectively combined with dolutegravir-based ART regimens.