St. John's wort labels often lack safety warnings

By Anne Harding

NEW YORK (Reuters Health) - In an analysis of product labels for St. John's wort preparations sold in the United States, investigators found that none mentioned all of the serious safety issues associated with using the herb.

People taking St. John's wort "can't rely on these labels to give them the safety-related information they need," Dr. Kevin A. Clauson of Nova Southeastern University in West Palm Beach, Florida, told Reuters Health.

And it's likely that other herbal medicines sold in the US have similarly inadequate labeling, he added.

St. John's wort, which is typically used to treat depression, is one of the most popular herbal medicines in North America and much of Europe. But taking the herb with AIDS medications or with drugs that suppress the immune system, or with oral contraceptives, or the blood-thinning drug warfarin can reduce the effectiveness of these drugs, Clauson and colleagues note in the journal BMC Complementary and Alternative Medicine.

St. John's wort is also not recommended for people with bipolar illness or those taking prescription antidepressants. Because the herb boosts levels of the brain chemical serotonin, taking it with drugs that work by the same mechanism can lead to a condition called serotonin syndrome, with consequences ranging from anxiety and sweating to death.

Clauson's team looked at labels of 74 St. John's wort products to find out how frequently these risks, along with the potential for the herb to cause excessive phototoxicity (sensitivity to light), were mentioned.

None of the products listed all of the potential drug interactions and contraindications the researchers had identified. Three mentioned seven of the eight criteria, while four listed no safety information at all.

The most common warnings included not to take the drug with antidepressants, mentioned on 23 percent of labels; phototoxicity (51.4 percent), and advice to consult a health care professional before taking the drug (87.8 percent).

Unfortunately, Clauson noted, doctors and pharmacists are often not aware of the risks associated with herbal medicines. "The consumers are going to want to be clear and persistent to make sure that their questions are not being dismissed and that the health care practitioner is going to give them specific information and not say it's not clear or there's no science behind it," he said.

"The misconception that natural equals safe is definitely still out there. People don't realize that a number of the most potent drugs we use today started out as plant products," he added. "Any herbal supplement or dietary supplement that works is going to have side effects or interactions -- period."

SOURCE: BMC Complementary and Alternative Medicine, online July 17, 2008.