Pharmacokinetics of the etonogestrel contraceptive implant in obese women.
OBJECTIVE
We sought to examine the pharmacokinetics and acceptability of the etonogestrel contraceptive implant in obese women.


METHODS
We developed and validated a plasma etonogestrel concentration assay and enrolled 13 obese (body mass index ≥30) women and 4 normal-weight (body mass index <25) women, who ensured comparability with historical controls. Etonogestrel concentrations were measured at 50-hour intervals through 300 hours postinsertion, then at 3 and 6 months to establish a pharmacokinetic curve.


RESULTS
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.


CONCLUSIONS
Obese women have lower plasma etonogestrel concentration than normal-weight women in the first 6 months after implant insertion. These findings should not be interpreted as decreased contraceptive effectiveness without additional considerations.
Department of Obstetrics and Gynecology, University of Chicago, IL 60637, USA.
Sara
S
Mornar
Lingtak-Neander
LN
Chan
Stephanie
S
Mistretta
Amy
A
Neustadt
Summer
S
Martins
Melissa
M
Gilliam
D000293:Adolescent; D000328:Adult; D019540:Area Under Curve; D044383:Black People; D003271:Contraceptive Agents, Female / Q000097:blood / Q000493:pharmacokinetics*; D017135:Desogestrel / Q000097:blood / Q000493:pharmacokinetics*; D005260:Female; D006801:Humans; D009765:Obesity / Q000097:blood*; D017060:Patient Satisfaction; D044465:White People; D055815:Young Adult; D001741:Black or African American
D003271:Contraceptive Agents, Female; C044815:etonogestrel; D017135:Desogestrel