The Effect of Topiramate on Etonogestrel Concentrations in Contraceptive Implant Users

Inclusion Criteria: * Healthy women, who have had an ENG implant for 12-36 months at the time of enrollment; * Will maintain their implant during the study without modifications. Exclusion Criteria: * Women who are taking any medications or supplements known to be 1. Cytochrome P-450 enzyme inducers, inhibitors, or substrates, and 2. are not willing to abstain from any of these medications or supplements during the entire course of the study. * Women with liver disease (i.e. hepatitis, fatty liver disease), and * Women with abnormal liver or renal function, or * Women with abnormal electrolytes on their screening blood work.