This updated Medicines Q&A evaluates the available evidence regarding an interaction between St John’s Wort and combined and progestogen only hormonal contraceptives.
- The interaction between combined oral contraceptives and SJW appears to be established. Its incidence is not known, but cases of breakthrough bleeding, menstrual irregularity and unplanned pregnancy have been reported. The MHRA has advised that SJW should not be used with hormonal contraceptives, except intrauterine devices, as there is a risk of contraceptive failure and unplanned pregnancy.
- Health professionals supplying hormonal contraception should ask women about their current and previous drug use including prescription, over the counter, herbal, recreational drugs and dietary supplements.
- Women using hormonal contraception should be informed about the potential for interactions with other drugs and the need to seek the advice of a health professional before starting any new drugs including herbal of dietary supplements.
- The FSRH in the UK, advise that women taking combined hormonal contraceptives, progestogen only pills or progestogen only implants should either avoid SJW or they should use an alternative form of contraception, unaffected by enzyme inducers e.g. progestogen only injection, intra-uterine devices (copper or levonorgestrel containing) or additional barrier methods.
- If St John’s Wort is continued, the general guidelines, produced by the FSRH for the use of liver enzyme inducers with hormonal contraceptives should be followed.