The
serum levels of ethinylestradiol are moderately reduced by
topiramate, which increases the risk of breakthrough bleeding and possible contraceptive failure in women taking combined hormonal
contraceptives. Similarly, emergency hormonal
contraceptives are considered to be less effective in those taking
topiramate.
Topiramate is a weak
enzyme inducer. However, the potential for contraceptive failure still exists. The manufacturers advise that patients should be told to report any changes in their bleeding patterns. For advice on the use of
enzyme inducers, such as
topiramate, and
contraceptives, see
contraceptives.