St John’s wort: interaction with hormonal contraceptives, including implants

St John’s wort interacts with hormonal contraceptives reducing the effectiveness and increasing the risk of unplanned pregnancy.

Article date: March 2014

St John’s wort (Hypericum perforatum L.) is a herbal medicine traditionally used to relieve slightly low mood and mild anxiety.

We have received two Yellow Card reports in the last quarter of 2013 of suspected interactions in women with implanted contraceptives containing etonogestrel (Nexplanon and Implanon). These women started taking St John’s wort and then had unplanned pregnancies. A total of 19 reports of suspected interactions between St John’s wort and hormonal contraceptives have been received through the Yellow Card scheme since 2000 (four for contraceptive implants and 15 for contraceptive pills). Of these suspected interactions, 15 cases resulted in unplanned pregnancies and the remaining four cases in association with contraceptive pills resulted in breakthrough bleeding without pregnancies.

There are warnings about these interactions and their consequences in the product information provided with all contraceptives and the authorised St John’s wort products. Some unlicensed products on the UK market or available online do not include the appropriate warnings regarding possible interactions. The lack of warnings does not mean these products do not interact with other products.

Advise women who are using combined and progestogen-only hormonal contraceptives that herbal products containing St John’s wort can decrease the effect of this contraceptive cover. Therefore, women taking hormonal contraception for pregnancy prevention should not take herbal products that contain St John’s wort. This applies to all hormonal contraceptives except intrauterine devices, for which there are currently no data.

Advice for healthcare professionals:

  • Advise women taking hormonal contraceptives for pregnancy prevention not to take herbal products containing St John’s wort
  • Encourage women to read the Patient Information Leaflet that comes with their hormonal contraceptive

Further information:

Guidance for consumers: the Traditional Herbal Registration (THR) certification mark

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