Phase I/II pharmacokinetic and pharmacodynamic evaluation of two levonorgestrel-only contraceptive patches in a...

To evaluate the pharmacokinetic and pharmacodynamic effects of two novel levonorgestrel (LNG)-only contraceptive patches.

This multi-center Phase I/II trial randomized participants to use a 7-day transdermal patch designed to deliver a 40 mcg or 75 mcg daily LNG dose for 11 consecutive weeks; randomization was stratified by body mass index (BMI) <32 or 32-40 kg/m². Evaluations occurred twice weekly for 5 weeks, then once weekly with supplemental visits for participants reporting a urinary LH surge. We evaluated pharmacokinetics via the weekly trough serum LNG concentrations (≥180 pg/mL considered therapeutic). The primary pharmacodynamic outcomes were cervical mucus and ovulation, evaluated using modified Insler cervical mucus scores and serum markers of ovulation.

Randomization yielded similar groups. Of 121 enrolled women, 117 contributed analyzable data. Overall, mean LNG concentrations achieved with use of the 75 mcg patch [value] were roughly double those seen with the 40 mcg dose. Concentrations achieved in higher-BMI women (BMI=32-40 kg/m²) were 50% lower compared to lower-BMI women for both patches. During the study, 94/117 (80%) participants had at least one LNG concentration <180 pg/mL. Insler scores were ≥5 at least once in 102/117 (87%) of participants, and ovulation occurred at least once in 81/117 (69%). Sixty participants (51%) had at least one ovulation following an Insler score ≥5; this occurred most frequently among higher-BMI participants using the lower-dose patch (19/25, 76%).

Women using two investigational LNG patches did not achieve consistent concentrations of LNG >180 pg/mL, an efficacy benchmark established in other studies with LNG implants, and they experienced high rates of ovulation as well as cervical mucus scores not supportive of high contraceptive efficacy.

The novel LNG-only patches in this study may not adequately decrease pregnancy risk, particularly for higher-BMI women. Future studies of LNG-only contraceptive patches will need to employ higher LNG doses and assess the acceptability and safety of such dosing.