Just because it’s natural doesn’t mean it’s safe

Question: My mother is taking herbal supplements. Her physician suspects they interacted with the other medications she’s on and may have contributed to her stroke. Are there guidelines for mixing prescribed medications with herbal supplements?

It is very important to talk with your doctor about herbal medicines that you may be taking.

Herbals are widely used, particularly by women 65 and older. Information from the Slone Survey – a comprehensive, ongoing population-based survey of medication use in the U.S. – shows that more than 25 per cent of older women take some form of herbal or other natural product. (Usage is likely similar in Canada).

Herbals are often taken to target chronic medical conditions. Frequently used products include glucosamine for arthritis, garlic for elevated cholesterol, and ginkgo biloba for improving memory.

Perhaps the reason herbal medicines are so popular is the misconception that because they are “natural”, they are entirely safe. This is not true!

Herbal medicines can have pharmacologic activity; numerous examples exist of commonly prescribed drug therapies that originally came from plants. The powerful opioid analgesics (pain-relieving medicines) first came from the poppy plant. The widely-used heart drug, digoxin, came from the foxglove plant. Some reports suggest herbal medicines may interact with prescribed drug therapies, leading to an adverse drug event. For example, ginkgo biloba may interact with warfarin, a prescribed blood thinner, causing an increased risk of bleeding. St. John’s wort, taken in combination with some forms of prescribed antidepressants, may make patients confused and agitated. Much more work is required to better understand these possible interactions.

It’s important to talk to your doctor before you start taking a herbal medicine. Survey data suggest that more than 50 per cent of people taking a herbal medicine do not bring this to their doctor’s attention. This may be because patients feel uncomfortable talking about herbals with their doctor. As part of a medication review, doctors and pharmacists need to routinely ask patients about their use of herbal and other natural products. It is important for patients to bring all their medications to their physician visit, including any natural health products, over- the-counter medications, and any other preparation they may be taking.
Despite the fact herbal medicines are widely used, there is relatively little high quality scientific evidence available to determine how patients can safely use these medicines. Recognizing this need, The National Centre for Complementary and Alternative Medicinewas established in 1998 as a new centre of the U.S. National Institutes of Health (NIH). While the quality of herbal medicine studies has improved over time, many clinical trials evaluating these therapies do not thoroughly describe the herbal medicine being studied. This is important because herbal medicines are natural products and the active ingredient can vary due to many factors, including how and where the product was grown.
A recent initiative led by investigators at the University of Toronto, and funded by the Canadian Institutes of Health Research, brought together an international group of experts to develop recommendations for standardizing the reporting of information about the herbal intervention being studied in clinical trials. Having better quality standardized studies will be a major step forward to creating the needed rigorous science in this area.

In the meantime, it’s important to remember that herbal medicines, like all prescribed drug therapies, have risks and benefits and should only be used under medical supervision.

Dr. Paula Rochon is a geriatrician and senior scientist at the Baycrest Geriatric Health Care System in Toronto. She has received peer-reviewed funding to study issues related to herbal medicines.

Ask The Doctor appears every other Tuesday in the Globe & Mail. E-mail questions to askthedoctor@globeandmail.ca