Etonogestrel contraceptive implant as emergency contraception: a mechanism of action pharmacodynamic pilot study.

OBJECTIVES: To evaluate the rate of ovulation suppression or delay by the etonogestrel contraceptive implant when inserted as theoretical emergency contraception. STUDY DESIGN: We conducted a pharmacodynamic pilot study among healthy, reproductive age females with regular menstrual cycles and proven prior ovulation. Starting cycle day 10, we performed serial ultrasounds on participants until identification of a dominant follicle (≥15mm). We then inserted contraceptive implants and performed laboratory and ultrasonographic monitoring every other day to identify if ovulation occurred. RESULTS: Six out of eight participants met pre-established criteria consistent with ovulation suppression or dysfunction after implant insertion. CONCLUSIONS: Our pharmacodynamic study supports further investigation of the etonogestrel implant as emergency contraception. IMPLICATIONS: An etonogestrel contraceptive implant is a potential option for an emergency contraception method. Because this study only evaluated a small sample, further research is needed to evaluate suppression in different BMI groups. GOV IDENTIFIER: NCT05237141.