MHRA highlights reduced contraceptive effect with St John's Wort

The MHRA has highlighted the reduction in efficacy of hormonal contraceptives, including the implant, when used in combination with St John's Wort.

The herbal medicine St John’s wort (Hypericum perforatum) helps relieve low mood and anxiety. | SCIENCE PHOTO LIBRARY
The herbal medicine St John’s wort (Hypericum perforatum) helps relieve low mood and anxiety. | SCIENCE PHOTO LIBRARY

The warning applies to all hormonal contraceptives except intrauterine devices, for which there is currently no data available.

Yellow Card reports

The advice was based on two 2013 Yellow Card reports of suspected interactions in women with implanted contraceptives containing etonogestrel (Nexplanon and its predecessor Implanon) who started taking St John’s wort.

Since 2000, a total of 19 reports of suspected adverse reactions between hormonal contraceptives (4 for contraceptive implants and 15 for contraceptive pills) and St John’s wort have been received by the agency. Overall 15 cases resulted in unplanned pregnancies and 4 in breakthrough bleeding without pregnancy.

Supplement contraindicated with hormonal contraceptives

The MHRA advises that women taking hormonal contraceptives for pregnancy prevention should not take herbal products containing St John’s wort. Healthcare professionals should encourage women to read the Patient Information Leaflet supplied with their hormonal contraceptive.

MHRA Drug Safety Update March 2014

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