Dietary Supplements with Prescription Drugs May Cause Complications

New research indicates that combining prescription medications with herbal and dietary supplements, such as St. John’s Wort or calcium, may cause potentially serious side effects.

According to a study published in the International Journal of Clinical Practice, herbal and dietary supplements may alter the pharmacokinetics of certain prescription medications, meaning the supplements affect the process of the drugs absorption, distribution, metabolization and elimination within the body.

Researchers studied 213 different herbal and botanical supplements, evaluating their interaction with 509 prescription medications. They found nearly 900 adverse reactions resulting from those interactions.

Herbal supplements like ginkgo and echinacea were more likely to have an adverse interaction with prescription medications than vitamins, amino acids or minerals such as iron or calcium, the study found.

Many of the complications included heart problems, chest and abdominal pains, and headaches. Patients taking medications for issues involving the cardiovascular system and central nervous system were more likely to experience adverse events.

Nearly 42 percent of the interactions were directly caused by the supplements altering the pharmacokinetics of the drugs and 26 percent of the adverse incidents were classified as “major” events.

The most common side effects of combining prescription drugs and supplements resulted in gastrointestinal issues, which comprised 16 percent of the events, and neurological problems, which accounted for nearly 15 percent of the cases.

Drugs such as aspirin, insulin, warfarin, ticlopidine, and diogoxin had the greatest amount of adverse interactions and the herbal supplements flaxseed, echinacea and yohimbe had the greatest amount of side effects.

Researchers estimate nearly 50 percent of patients suffering from chronic diseases who use prescribed medications also use herbal remedies or other dietary supplements, despite the fact that they are not generally regulated by the FDA.

“Our current knowledge is still woefully incomplete,” said Edzard Ernst, the study’s author and Emeritus Professor of the University of Exeter.

Scientists say the findings are the “tip of the iceberg,” of much needed research in this area and are also calling for more government control over the use of such herbal and dietary supplements. Researchers also stress the dangers of combining prescription medications with herbal remedies and dietary supplements.

The findings follow a recent report by the consumer watchdog group Public Citizen, which highlighted research from the Journal of Parenteral & Enteral Nutrition that found dietary supplements provided little benefit to healthy adults.

Researchers concluded that the use of many supplements may also be harmful. The only dietary supplement which they determined may benefit patients were Vitamin D and omega-3 fatty acids.