Oral contraceptives and rifampicin

An alternative method of contraception to the combined oral contraceptive pill is best used if a woman is on rifampicin - this drug is a very powerful enzyme inducer and a five-fold increase in the rate of oestrogen metabolism has been observed in some women.

• the BNF suggests that ".. rifampicin and rifabutin are such potent enzyme-inducing drugs that an alternative method of contraception (such as an IUD) is always recommended. Since enzyme activity does not return to normal for several weeks after stopping an enzyme-inducing drug, appropriate contraceptive measures are required for 4 to 8 weeks after stopping .."

Reference:

1. The Practitioner (1999), 243, 462-72.
2. BNF 7.3.1