Residual hormone levels in used contraceptive rings as a measurement of adherence to vaginal ring use

Objective This study sought to measure residual contraceptive hormone levels in vaginal rings as an adherence marker for monitoring product use in clinical trials. Study design Residual etonogestrel and ethinyl estradiol levels from used NuvaRings® of 26 self-reported adherent women enrolled in a clinical trial of vaginal ring acceptability were compared to those from 16 women who used NuvaRing® as their contraceptive choice. Results Twenty-one (81%) clinical trial rings had contraceptive hormone levels within the range of those used as a contraceptive choice. Five returned rings had unused or discordant levels of residual contraceptive hormones. Conclusion Residual vaginal ring drug levels could help assess adherence in clinical trials.