Britain Issues Warning on Use of St. John’s Wort

LONDON — Britain’s Health Department issued a warning Wednesday over the risks of taking St. John’s wort after studies showed the popular herbal remedy may interfere with certain prescription drugs.

The Health Department said the herb, used to relieve mild depression, may interfere with medicines prescribed to treat HIV infection, heart conditions, blood clots, asthma, depression and migraine headaches.

The herb also may interfere with the oral contraceptive pill, the department said, as well as medications given to transplant patients.

The Medicines Control Agency is consulting with alternative medicine organizations and trade associations on providing information with the unlicensed remedy, including labeling changes, the government said.

All prescription drugs most likely to interact with St. John’s wort also will include new warnings about possible drug interactions.

The warning comes on the heels of two studies published last month in The Lancet medical journal that found the herb dulls the effectiveness of both the HIV medicine indinavir and the drug cyclosporin, used to suppress the immune systems of transplant patients so their bodies do not reject the new organs.