Topiramate, introduced as an antiepileptic drug (AED), is currently most widely used for prevention of migraine headaches.
Because reproductive-aged women represent a population in which migraines are prevalent, clinicians need guidance to help women taking topiramate make sound contraceptive choices.
Several issues are relevant here. First, women who have migraines with aura should avoid estrogen-containing contraceptive pills, patches, and rings. Instead, progestin-only methods, including the contraceptive implant, may be recommended to patients with migraines.
Second, because topiramate, as with a number of other AEDs, is a teratogen, women using this medication need highly effective contraception. This consideration may also lead clinicians to recommend use of the implant in women with migraines.
Finally, topiramate, along with other AEDs (phenytoin, carbamazepine, barbiturates, primidone, and oxcarbazepine) induces hepatic enzymes, which results in reduced serum contraceptive steroid levels.
Because there is uncertainty regarding the degree to which the use of topiramate reduces serum levels of etonogestrel (the progestin released by the implant), investigators performed a prospective study to assess the pharmacokinetic impact of topiramate in women with the implant.
Ongoing users of contraceptive implants who agreed to use additional nonhormonal contraception were recruited to a 6-week study, during which they took topiramate and periodically had blood drawn.
Overall, use of topiramate was found to lower serum etonogestrel levels from baseline on a dose-related basis. At study completion, almost one third of study participants were found to have serum progestin levels lower than the threshold associated with predictable ovulation suppression.
The results of this carefully conducted study support guidance from the Centers for Disease Control and Prevention that women seeking contraception and using topiramate or other enzyme-inducing AEDs should be encouraged to use intrauterine devices or injectable contraception. The contraceptive efficacy of these latter methods is not diminished by concomitant use of enzyme inducers.
I am Andrew Kaunitz. Please take care of yourself, and each other.
SOURCE: medscape.com, Andrew M. Kaunitz, MD