Depot medroxyprogesterone acetate concentrations in patients with and without use of anti-seizure medications

Objectives To measure plasma concentrations of medroxyprogesterone acetate (MPA) in users with epilepsy treated with anti-seizure medications and compare these to MPA concentrations in those without epilepsy. Methods For this multi-site cross-sectional study, we obtained a single blood sample from those with epilepsy treated with various anti-seizure medications (n=18) within the week before their next depot medroxyprogesterone (DMPA) injection. Among the participants without epilepsy (n=20), 10 similarly were scheduled within the week prior to the next injection, and 10 were scheduled at earlier intervals to attempt to balance the time intervals between groups. MPA concentrations were determined by a validated assay. Results MPA concentrations were similar among those with epilepsy and controls, and between groups with and without use of enzyme-inducing medications. The lowest MPA concentrations, under 0.07 ng/mL, were observed among two of eight using enzyme-inducing anti-seizure medications; one of 10 using non-inducing medications, and one of 19 controls had concentrations below 0.2 ng/mL. Conclusions In this exploratory study, lower MPA concentrations in some participants using enzyme-inducing anti-seizure medications suggest a potential interaction that could reduce DMPA efficacy.