A study conducted in Canada by University of Alberta scientists suggests that natural remedies could cause many more harmful side effects than once thought. Mixing herbal medicines and prescriptions could pose undiscovered health risks because many negative reactions are not being reported or tracked.
Pharmacists seldom report adverse reactions experienced by people who use natural health products along with prescription drugs, even though almost half suspect they have seen patients who have had negative side-effects.
AdvertisementThe adverse effects of taking prescription drugs with natural health products are dramatically under-reported or not reported at all, so their potential risks may be underestimated by health-care professionals and the public, the study found.
"People look at risks based on what's known. If it's not being reported, it can't be known," said Dr. Sunita Vohra, an associate professor of pediatrics at the University of Alberta and the study's lead author, which was reported in this month's edition of the medical journal The Annals of Pharmacotherapy. "Lack of reporting is a major issue of our knowledge of harms," "If we don't report what natural products react with what medications, how can we effectively counsel patients in what they should avoid combining?"
Vohra said 71 per cent of Canadians use natural health products, such as St. John's wort, echinacea, Chinese medicines, vitamins, herbal remedies or garlic pills. Many of those people also have chronic health issues and take prescription medications, yet because so little research has been done on the topic, they and health-care providers don't understand the potential risks of mixing the substances.
For instance, 95 per cent of the pharmacist respondents said they didn't feel comfortable counseling patients on the possible side-effects of combining garlic with the HIV medication Ritonavir even though reports suggest garlic lowers the concentration of the prescribed drug in the blood. Half had not heard that organ transplant patients taking the anti-rejection drug Cyclosporine along with St. John's wort -- commonly used to fight depression -- could cause them to reject their new organ. Many didn't recognize that St. John's wort can cause failure of oral contraceptives, or that cranberry juice -- taken medically to calm bladder infections -- can make the blood-thinning drug Warfarin unstable.
The findings point to an "urgent need" for additional safety data on herbal and other natural products used by millions of Canadians, said the University of Alberta scientists behind the research.
"This [study] leads us to believe that natural-health product [NHP] adverse events are far more common than previously suspected,"
The lack of reporting of safety problems by health professionals is aggravated by the fact that patients assume natural treatments will cause them no harm, argue the researchers at U of A's Complementary and Alternative Research and Education (CARE) program.
Vohra says "Just because it came from nature doesn't mean it is not active," "It means that, in fact, it may be active, it may be effective, but may also be potentially harmful."
A representative of the Canadian natural-health industry said the research underlines the need for more education, but cautioned against jumping to conclusions about the extent of natural-health side effects until more research is done. Meanwhile, there is increasing evidence of the benefits of natural treatments, said Penelope Marrett, president of the Canadian Health Food Association.
Dr. Vohra, a pediatrician who also has degrees in pharmacology and epidemiology, and her team recently were awarded federal funding for a new pilot project that will see 16 drug stores across the country systematically inquire about and report natural-cure mishaps.
People should make their doctors and pharmacists aware of all the traditional and complementary medicines they are taking, as well as any alternative therapies they are involved with. And health-care workers should routinely ask about the products.
Health Canada is doing its own research on specific interactions between drugs and natural health products, as well as trying to better educate pharmacists and consumers about the issues.