Canadian researchers have cautioned that the adverse effects of the simultaneous use of prescription drugs and natural health products (NHP) are being under-reported, and that health-care professionals and the public may be underestimating the potential risks of combining the two therapies.
Researchers at the University of Alberta in Edmonton conducted a survey of 132 pharmacists. While 47 per cent of pharmacists reported that they had encountered a patient with a suspected adverse event, only 1.5 per cent reported this to Health Canada, the department of the government of Canada with responsibility for national public health.
In contrast, 19 per cent of the pharmacists reported adverse reactions to prescription or non-prescription drugs.
"The data show that adverse events are not being reported or are being under-reported at a dramatic rate," said Dr. Sunita Vohra, one of the study authors and an Associate Professor of Paediatrics at the University of Alberta.
"Natural health products should be treated with due respect," Dr. Vohra added.
She further said that the use of natural health products may be effective, but they may have side effects too. These adverse reactions may range from mild rashes and headaches to much more serious effects, if patients are also using prescription medication like blood thinners or insulin.
While about 50,000 natural health products are sold in Canada, the majority of pharmacists felt that they knew enough about just two drug-health product interactions to counsel patients.
The survey also revealed that most pharmacists spent up to 30 minutes per day counselling patients on the use of natural health products, while only five per cent of patients who purchase such products asked about potential drug interactions.
"The public is less likely to see natural health products as risky," Dr. Vohra noted.
The lack of available data on interactions makes it difficult to provide patients and health care workers with useful advice for managing adverse reactions associated with these products.
"To improve patient safety, new ways of capturing data are necessary," Dr. Vohra said, adding that possible ways to do that include active surveillance to monitor for harms.
"Select pharmacies agree to be 'sentinel sites', actively asking every patient about possible adverse events, and reporting all data so we can learn which NHP-drug combinations are safe, and which aren't," she added.
The study, co-authored by researchers from the University of Toronto, has been published in The Annals of Pharmacotherapy.