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News

Herbal supplements may cause risks for patients anticipating surgeries

University Of Chicago : 12 August, 2007  (Technical Article)
A new study by researchers in the University Medical Center gives patients and physicians specific recommendations for discontinuing the use of herbal medications prior to surgery. In the Journal of the American Medical Association, the three physicians assess the interactions between herbs, anesthesia and surgery and suggest ways to reduce the associated risks.
The authors wrote that their goal is to provide a framework for physicians “practicing in the current environment of widespread herbal use” and to encourage patients and physicians to discuss the topic openly and in detail prior to surgery.

“While most of these substances appear to be safe for healthy people, for surgical patients they can affect sedation, pain control, bleeding, heart function, metabolism, immunity and recovery in ways that we are just beginning to understand,” said study author Chun-Su Yuan, Assistant Professor in Anesthesia & Critical Care and a member of the Tang Center for Herbal Medicine Research at the University.

Studies suggest that as many as one-third of pre-surgical patients take herbal medications, but that many of those patients fail to disclose herbal use during pre-operative assessment, even when prompted. Further, physicians often are unsure what to do with the information.

“Physicians need to specifically ask patients about herbal medication use,” said co-author Jonathan Moss, Professor in Anesthesia & Critical Care. “Many patients think of herbal medications not as supplements but as drugs. Other patients may not want to admit to their use to physicians. But in order to optimize patient safety and pain control during and after surgery, we need to know what herbal as well as over-the-counter or prescription drugs each patient takes.”

Despite their reputation as “mild” or “natural,” herbal medications can speed up or slow down the heart rate, inhibit blood clotting, alter the immune system and change the effects and duration of anesthesia.

The American Society of Anesthesiologists has recognized the potential for adverse reactions and suggests that patients stop taking all herbal medications two weeks before surgery. This advice may be difficult to implement, however, because most pre-operative evaluations occur only a few days prior to surgery.

So the Chicago researchers began to search for more targeted recommendations. Although there are more than 1,500 herbal medications sold in the United States, they focused on the eight most commonly used herbs, echinacea, ephedra, garlic, gingko, ginseng, kava, St. John’s wort and valerian, which account for 50 percent of all single-herb preparations sold.

The authors found, first of all, a shortage of clinically relevant information. There were no randomized, controlled trials that evaluated the effects of prior herbal medicine use on the period immediately before, during and after surgery.

However, by reviewing the biology of the compounds as well as all studies, case reports, and reviews addressing the safety and pharmacological effects of these eight medications they came up with the following recommendations:

The authors caution that even this study has many gaps. Because they are regulated as dietary supplements rather than medications, herbal medications do not undergo the safety and efficacy testing required for new drugs. Further, unlike pharmaceuticals, there is no mechanism to track adverse events caused by herbs.

Herbal medications are even more difficult to study because the ingredients tend to vary enormously from maker to maker and even from lot to lot. Potency and purity are inconsistent, and product labels are not always accurate.

In fact, Yuan, who studies the effects of ginseng, has had to work closely with a Wisconsin supplier to obtain consistent supplies of that herb for his research.

Many physicians remain unaware of potential risks associated with herbal medications or how they interact with other drugs, noted the authors. Medical schools are just beginning to teach students about herbal preparations and to study their effects systematically.

“If patients use them, and we know they do, then we need to know what to expect, how to prevent problems, especially during surgery, and how to respond when something goes wrong,” added co-author Michael Ang-Lee, Senior Resident in Anesthesia & Critical Care.

The authors have appended a list of Web sites with reliable information on herbal medicines, including the FDA’s Center for Food Safety and Applied Nutrition, the National Center for Complementary and Alternative Medicine, the USDA’s Agricultural Research Service, Quackwatch, the National Council Against Health Fraud, HerbMed and ConsumerLab.
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