Combined hormonal
contraceptives, progestogen-only pills and emergency hormonal
contraceptives are less reliable during treatment with
carbamazepine. Breakthrough bleeding and spotting can take place and unintended pregnancies have occurred. Controlled studies have shown that
carbamazepine can reduce contraceptive steroid levels.
Because of the consequences of an unwanted pregnancy, especially with drugs that may cause foetal abnormalities, adjustments should be made. For general advice on the use of
enzyme inducers, such as
carbamazepine, and
contraceptives, see
contraceptives