Prescription Drugs and Dietary Supplements Can Make an Unhappy Marriage

As many people know, grapefruit is a delicious and healthful fruit that can be very bad medicine when consumed with certain drugs. One of its chemical constituents, furanocoumarin, interacts with a variety of drugs that can enhance or diminish their effects. Among the more common drugs not to be consumed with grapefruit are those taken for high cholesterol (Lipitor, Zocor), high blood pressure (Plendil, Procardia), anxiety (Buspirone), depression (Zoloft) and seizures (Carbatrol, Tegretol).

Like grapefruit, many dietary supplements seem benign, but also might pose health risks when taken in the company of certain prescription drugs. A study published recently in the International Journal of Clinical Practice concluded that although interactions between drugs and herbs and dietary supplements (HDS) affect relatively few medications, health-care practitioners should be certain to address the issue when prescribing drugs to patients to avoid adverse events. We would add that patients should inquire about their safety.

More than 1 in 4 adverse incidents documented in the study were classified as “major” events. Complications included heart problems, chest and abdominal pain and headaches.

Medications affecting the central nervous system or cardiovascular system had more documented interactions with HDS. Flaxseed, Echinacea and yohimbe were more likely to cause problematic side effects when taken with drugs than were vitamins and minerals.

Researchers studied 1,491 unique pairs of HDS-drug interactions, 213separate HDS and 509 medications. They documented 882 negative interactions. HDS products containing St. John’s wort, magnesium, calcium, iron and ginkgo notched the most interactions with medications. Among the drugs, warfarin (Coumadin), insulin, aspirin, digoxin (Digitek, Lanoxin), and ticlopidine (Ticlid) had the most interactions with HDS.

As noted on, nearly half of all patients with chronic diseases who use prescription drugs also take herbs or dietary supplements. The latter are not regulated by the FDA. AboutLawsuits referred to a report by consumer watchdog Public Citizen that determined there was little benefit to healthy adults in taking HDS. Like many scientists, Public Citizen advocates for greater regulatory oversight of dietary supplements.

But the lack of systemic review of the industry and its products’ effects on human health does not excuse doctors and patients from taking responsibility for what they prescribe or consume, respectively. We’ve written about the folly of vitamin supplementation, and our newsletter “Eat, Drink and Be Wary: The Truth About Diet Supplements and Sports Drinks” offers a wider discussion.

Make sure your doctor has a full record of all medicines-prescription and over-the-counter-you take, as well as any vitamins, minerals or dietary supplements. If you are prescribed a new drug, remind him or her of what you take, and ask if it’s safe to take them with the new medication.

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