St John's wort may reduce the pill's effectiveness
22 February 2002
Women who use the herbal anti-depressant St John's wort while taking the contraceptive pill risk becoming pregnant, a Swedish medical agency has warned.
The country's pharmaceutical regulator, the Medical Products Agency (MPA) issued a new warning about the herbal extract after 2 women, aged 28 and 31, became pregnant while they were on oral contraceptives.
St John's wort contains hyperfourin, a substance that affects drug breakdown in the liver.
Per Claeson, from the MPA, said: 'We have heard of several case reports of pregnancies occurring in Sweden and the UK, and drug interactions also in Switzerland and Germany
'We issued advice on this in 1999 but we are making it clearer now because we are more sure,' Mr Claeson added.
In light of the most recent scientific evidence, Sweden has now made it compulsory for all St John's wort products except tea to carry a warning label about drug interactions.
St John's wort, a supplement taken to alleviate mild to moderate depression, is known to counteract the effect of certain drugs, including hormone-based contraceptives.
St John's wort is also said to reduce the effectiveness of HIV medicines, blood-thickening drugs and cyclosporine.
Last Reviewed: 19 February 2002
- 1. Medical Observer Weekly 15/02/02
