oral contraceptives and St John's wort
St John's wort (SJW) interacts with oral contraceptives and may lead to reduced blood levels with a risk of breakthrough bleeding and unplanned pregnancy.
It is advised that SJW is stopped if a patient is taking an oral contraceptive.
The MHRA states "...St John's wort interacts with hormonal contraceptives. This interaction reduces the effectiveness of these contraceptives and increases the risk of unplanned pregnancy. This applies to all hormonal contraceptives except intrauterine devices, for which there are currently no data...
Advise women taking hormonal contraceptives for pregnancy prevention not to take herbal products containing St John's wort..."
- MRHA (January 2014). Drug Safety Update - St John's wort: interaction with hormonal contraceptives, including implants- reduced contraceptive effect
Last reviewed 01/2018