Double vs single-dose etonogestrel implant with efavirenz-based antiretroviral therapy

Concomitant use of efavirenz-based antiretroviral therapy and a standard-dose etonogestrel contraceptive implant causes 82% lower etonogestrel exposure than women who do not receive antiretroviral therapy. Higher rates of unintended pregnancies are observed when contraceptive implants are combined with efavirenz. A recent study hypothesized that placing two etonogestrel implants in women taking efavirenz-based antiretroviral therapy could increase etonogestrel exposure and improve contraceptive efficacy.

The study observed-

• Participation of 72 women with a median age of 31 years. 
• Study discontinuation by two participants in the control group due to undetected pregnancy at entry in one and clinically significant depression in another participant. 
• Forty-seven ovulations over 104 person-months (45%) in 25 of 34 participants in the control group and two ovulations over 108 person-months (2%) in 2 of 36 participants in the double implant group.
• Reduction in the odds of ovulation by 97.7% in the double implant group over 48 weeks. 
• >2-fold higher Etonogestrel concentration in the double implant group than in the controls at each time point, with a geometric mean ratio of 2.83 at week 48. 
• No differences in the adverse events between groups
• No participants discontinued the trial because of adverse events.

This study shows that over 48 weeks of combined use, placing two etonogestrel implants suppressed ovulation and increased plasma etonogestrel exposure than one etonogestrel implant among women on efavirenz-based antiretroviral therapy. Doubling the dose of etonogestrel during efavirenz-based antiretroviral therapy could improve contraceptive effectiveness.

Chappell CA, Lamorde M, Nakalema S, et al. A randomized trial of double vs single-dose etonogestrel implant to overcome the interaction with efavirenz-based antiretroviral therapy. American Journal of Obstetrics and Gynecology. 2024;231(2):P242.e1-242.e9