Does St John’s Wort interact with Emergency Hormonal Contraception?

Tim Meadows, Medicines Information Pharmacist, Midlands and East Medicines Advice Service (East site)Source UKMiPublished

This updated Medicines Q&A evaluates the available evidence regarding an interaction between St John’s Wort and emergency hormonal contraception.


  • Levonorgestrel is a progestogen commonly used in hormonal contraceptives to inhibit ovulation. Ulipristal acetate is a selective progesterone receptor modulator.
  • St John’s Wort (SJW) is the common name for the plant Hypericum perforatum and is a popular herbal remedy for the management of mild to moderate depression.
  • SJW has several active constituents including hypericin, hyperforin and adhyperforin. Hyperforin is a potent inducer of the cytochrome P450 enzymes, particularly CYP3A4, which appears to be the major route for inactivation of most contraceptive steroids, including levonorgestrel and also ulpristal acetate.
  • Patients currently taking SJW or who have taken it in the past 4 weeks who require emergency contraception should be recommended to use a copper intrauterine device.
  • If this is not possible, a double-dose of levonorgestrel-containing EHC (3mg as a single dose) can be used, although the interaction between double-dose levonorgestrel and enzyme-inducers has not be studied.
  • The use of ulipristal acetate EHC is not recommended in patients who are taking or who have taken SJW in the past 4 weeks.