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April 15, 2014

Natural health products: Beware of drug interactions

(By: Protégez-Vous)

Natural health products can interact with other medications you may be taking. Always check with your doctor or pharmacist before using this type of product.

Use of natural health products (NHPs) has increased around the world, with several studies showing that people are now taking them in combination with standard medications. For the past 15 years or so, but increasingly since 2000, researchers have been reviewing interactions between drugs and NHPs. In 2000, they noted that St. John’s Wort, a plant used to treat depression, can cause dangerous side effects when taken by organ transplant recipients or patients with HIV.

Experts admit that the issue of drug interactions and NHPs is not yet fully understood and requires further study. Without being alarmist, it has nevertheless become sufficiently clear that NHPs should be used with prudence. In fact, even short-term use can lead to adverse interactions.

Examples of potential interactions

Some NHPs can increase, reduce or hinder the effects of certain drugs. Valerian, for instance, can augment the sleep-inducing properties of sleeping pills. Similarly, St. John’s Wort should never be taken with antidepressants, such as Prozac or Zoloft, since their active components all act on the levels of serotonin in the brain.

In many cases, NHPs change the way in which synthetic drugs are metabolized in the body and affects how they are absorbed. What this means is that NHPs can increase or reduce the concentration of a drug in the body. This is especially dangerous with drugs that have a narrow therapeutic index (e.g. warfarin, Coumadin), that is where there is little difference between the therapeutic and toxic doses. St. John’s Wort, ginseng, ginkgo biloba and garlic (in that order) are the plants most likely to trigger this type of serious interaction. 

Who is most at risk? 

Seniors and children and adults who have a chronic disease or problems with certain medications are some of the consumers taking NHPs and prescription drugs. Since their health is more fragile, they should talk openly about their NHP and medication intake with a well-informed health professional.

Women who are pregnant or breastfeeding must also exercise caution with natural products, given their potentially serious side effects. Many plants, such as pennyroyal mint and feverfew, are known to stimulate uterine contractions and should be avoided during pregnancy. If you are pregnant or breastfeeding, never take any type of supplement without first consulting your doctor or pharmacist.

Keep in mind that interactions can always occur when mixing NHPs and medications, even if you are in good health. A prime example: St. John’s Wort can interfere with the effectiveness of the birth control pill.

How to prevent interactions

To avoid negative interactions between NHPs and prescription medications, nothing beats communication – with your doctor and pharmacist, that is! Don’t hesitate to tell them about your use of supplements. This is usually second nature for people already taking prescription medications with interaction risks – not so for people who take medication only once in a while. They should be especially vigilant about discussing this issue with their health professional.

Declaring unwanted side effects

Any serious or unexpected adverse reactions to a therapeutic product, whether natural or synthetic, should be reported to Heath Canada – and that includes drug-NHP interactions. To do so, complete the MedEffect reporting form.

Source: Guide pratique des produits de santé naturels, Protégez-Vous, 2011 (In French only)

To learn more:

The Health Canada Natural Health Products Database
Les produits de santé naturels : parlez-en avec votre médecin ou votre pharmacien, Collège des médecins (In French only)
Produits de santé naturels et médicaments : un mélange parfois risqué, Option Consommateur (In French only)
Grossesse et produits de santé naturels, Protégez-Vous, July 2012 (In French only)

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