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Pharmacokinetics of the Etonogestrel Contraceptive Implant in Obese Women
American Journal of Obstetrics and Gynecology, 05/15/2012
Clinical Article
Mornar S et al. – Obese women have lower plasma etonogestrel concentration than normal–weight women in the first six months after implant insertion. These findings should not be interpreted as decreased contraceptive effectiveness without additional considerations.
Methods- Authors developed and validated a plasma etonogestrel concentration assay and enrolled 13 obese (BMI≥30) women and 4 normal–weight (BMI<25) women, who ensured comparability with historical controls.
- Etonogestrel concentrations were measured at 50–hour intervals through 300 hours post–insertion, then at 3 and 6 months to establish a pharmacokinetic curve.
- All obese participants were African American, while all normal–weight participants were white.
- Across time, the plasma etonogestrel concentrations in obese women were lower than published values for normal–weight women and 31–63% lower than in the normal–weight study cohort, although these differences were not statistically significant.
- The implant device was found highly acceptable among obese women.