Dietary supplements can cause harmful reactions with ...

URL: http://www.news.harvard.edu/gazette/2006/10.26/11-herbs.html

Dietary supplements can cause harmful reactions with prescription medicines

By William J. Cromie
Harvard News Office


Paula Gardiner, a research fellow at HMS, says concern has grown about the interaction between prescription drugs and dietary supplements. (Staff photo Jon Chase/Harvard News Office)

More than one of every five people who take prescription drugs also use dietary supplements, like ginseng and gingko, without telling their doctors. Such combinations may lead to harmful results, such as interfering with the action of prescription medications taken for conditions ranging from insomnia to heart disease, cancer, and arthritis.

"Amid increasing numbers of reports describing interactions between prescription drugs and nonvitamin dietary supplements, concern has grown regarding the troublesome possibility of adverse effects," notes Paula Gardiner, a research fellow at Harvard Medical School. She and her colleagues at Harvard-affiliated Beth Israel-Deaconess Medical Center in Boston recently completed a study to determine how many and which people in the United States mix the two.

Using results from the 2002 National Health Interview Survey, the latest available, they conclude that 21 percent of the estimated 135 million adults in this country who took prescription drugs also used nonvitamin supplements without discussing the combinations with their doctors. This total of 28 million people was up from an estimated 15 million in 1997. Now that the U.S. population has reached 300 million, the number in 2006 is probably higher still.

The most commonly used supplements were echinacea (for colds and flu), ginseng (to increase stamina and energy), gingko (for memory enhancement), garlic (to lower cholesterol and blood pressure), glucosamine chondroitin (for arthritis), and St. John's wort (to treat mild depression).

The highest users were those with chronic but not life-threatening conditions such as menopause, stomach and intestinal woes, headaches, and insomnia. Lowest users, fortunately, included those with life-threatening conditions such as heart disease, stroke, and diabetes.

Who took what
According the study, users of supplements plus prescription drugs are most likely to be women, Hispanics, those with a college education, residents of Western states, the uninsured, former smokers, fitness center customers, and those without a regular source of primary medical care. Elderly people on prescription meds were found to be less prone to supplement use than younger people.

These patients were part of 31,044 individuals who responded to the national health survey. Sixty-seven percent (20,800) of them took prescription drugs during the preceding year, and 21 percent (6,519) took nonvitamin supplements at the same time.

Roughly one-third of those taking prescriptions for menopause problems, stomach and intestinal disorders, and severe or migraine headaches also took herbal and other dietary supplements. Less than half that number, who were being treated for congestive heart failure, heart disease, and a history of heart attacks, used such substances. Ten percent of those taking prescription meds for asthma used echinacea. Five percent added garlic to their medications for high cholesterol or irregular heartbeat.

An estimated 1.2 million prescription drug takers also used St. John's wort despite the fact that it has been proven to lower the efficacy of a wide range of medications including blood thinners, oral contraceptives, and compounds to treat heart failure, mood disorder, AIDS, stroke, and heart attack.

Hazardous combinations
Many of the herbs and dietary supplements included in the national survey, like chamomile and peppermint, are safe for most everyone. But several can lead to well-known adverse reactions. This is especially true among people with liver and kidney diseases who may have problems metabolizing herbs and supplements.

"Despite this," Gardiner notes, "we found that 26 percent of patients with liver disease and 19 percent with kidney disease were using nonvitamin dietary supplements and a prescription medication at the time of the survey. Unfortunately, there is little evidence to provide clinicians with guidance on the safety of using these supplements in patients with liver and kidney problems."

Gardiner and her colleagues also express concern about combining dietary supplements and prescription drugs with narrow margins of safety. These include medications such as digoxin, prescribed for heart failure and irregular heartbeat; warfarin, for blood clots; and valporic acid, an anti-seizure drug used to treat epilepsy. "In our analysis, patients with seizure disorders, irregular heartbeats, and congestive heart failure had relatively high non-vitamin dietary supplement use," Gardiner says.

Some of the supplements included in the Harvard analysis have been banned. In August, the 10th U.S. Circuit Court of Appeals in Denver upheld a 2003 Food and Drug Administration ruling that ephedra is illegal in the United States. The FDA said that risks associated with its use for weight loss and athletic enhancement outweigh any potential benefits.

Kava is another product on the unwanted list because it has been linked to liver poisoning. Regulatory agencies in Germany, Switzerland, France, Canada, and the United Kingdom have taken actions ranging from warning consumers about its risks to removing kava-containing products from market shelves. However, kava is still legally available in the United States, and 6 percent of those who participated in the survey said they used it along with prescribed drugs.

Given the high frequency of mixing the two types of compounds, the Harvard researchers maintain that "physicians need to know about potential adverse effects or interactions associated with any prescription medication or dietary supplements. Such supplements have complex mechanisms of action that need to be understood. Health care professionals must regularly ask their patients with chronic conditions and prescription medications about supplement use."

And patients taking such substances should tell all the professionals who care for their health what supplements and daily doses they consume, something that the majority of people evidently do not do.

URL: http://www.news.harvard.edu/gazette/2006/10.26/11-herbs.html

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