Patients on anti-clotting drugs who take herbal and dietary supplements may be putting themselves at risk without their doctors’ knowledge, researchers said. More than two-thirds of 100 patients surveyed said they used over-the-counter products such as multivitamins, glucosamine and fish oil while taking the anti-clotting drug warfarin, also sold as Coumadin by New York-based Bristol-Myers Squibb Co., according to a study presented today. Sixty-three percent didn’t talk to their doctor or pharmacist before starting the supplements, said researchers releasing the results at the American Heart Association’s annual meeting in Chicago.
Previous studies have found that herbal and dietary supplements can change the effectiveness of anti-clotting medicines, increasing the risk of strokes or bleeding, study author Jennifer Strohecker said. Today’s findings show that doctors and patients need to communicate about the use of supplements to prevent dangerous interactions, she said.
“One of the biggest issues is that people do not view supplements as drugs,” said Strohecker, a clinical pharmacist at Intermountain Healthcare in Salt Lake City, in a Nov. 9 telephone interview. Patients don’t think to tell their doctors they are taking supplements when the doctor asks if they’re using any new medications, she said.
U.S. sales of anticoagulants including warfarin were $276.6 million in 2009, according to IMS Health, a Norwalk, Connecticut-based research firm. Sales this year reached $134.7 million through June, according to IMS.
Regular Monitoring
Warfarin, developed as a rat poison, has been a standard anti-clotting treatment since it was approved in 1954. The drug requires regular blood tests to ensure a safe, effective dose. Strohecker said warfarin is responsible for the most emergency room visits by older patients due to drug-related complications.
Dietary supplements include minerals, vitamins and herbs used in a quest for greater health, according to the U.S. Food and Drug Administration. Among the most popular products are Echinacea, garlic, ginkgo biloba, ginseng and St. John’s wort, according to the American Academy of Family Physicians. Health supplements are sold over the counter in retail stores and aren’t regulated as drugs.
A study presented in May at the annual meeting of the Heart Rhythm Society in Denver, Colorado, found that people taking warfarin may have a higher risk of excessive bleeding or blood clots when using supplements containing gingko, garlic and fish oil. The researchers, including Strohecker, found that cranberry and glucosamine, for example, make the medication more potent, while ginseng and green tea extract make it too weak and ineffective at preventing clots in blood vessels.
Survey Results
In today’s study, 100 patients taking warfarin were surveyed. One-third of those taking the medicine said doctors asked about herbal supplement use, and 92 percent said they would tell their physicians if asked. Almost half said they didn’t consider the supplements to be drugs.
The most common health aids taken by those in the study were multivitamins and high-dose vitamins, glucosamine and chondroitin for the joints, and fish oil and coenzyme Q10 for the heart, Strohecker said.
Consumer education and improved doctor-patient communication are needed to reduce risk, she said, as well as statements on supplements warning they may interact with certain medicines.