Ginkgo is probably OK up until about 36 hours before the operating room, but garlic and ginseng should be halted at least seven days before planned surgery, according to new guidelines.
Physicians at the University of Chicago prepared the guidelines after extensively reviewing research done on the physical effects and safety of eight commonly used herbal medicines.
It's estimated that as many as one-third of pre-surgical patients are taking herbal medications, but many fail to tell doctors they're using the supplements, even during pre-surgery assessments. And many doctors are unsure what to do with the information if patients do tell them about the use.
"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 Dr. Chun-Su Yuan.
Yuan is associate director of the Tang Center for Herbal Medicine Research at the university and senior author of the report published Wednesday in The Journal of the American Medical Association.
The researchers said their report is an effort to provide some framework for physicians to consider herbal use when planning surgery, and to encourage open discussion between doctor and patient before an operation.
Despite their reputation as "mild" or "natural" products, and although they are regulated as "dietary supplements" rather than as medicines, "herbs are actually no more than diluted drugs," said leading herbal expert Varro Tyler, a professor emeritus at Purdue University. "And as is the case with other drugs, administration of herbs may produce undesirable side effects," he added.
The Chicago researchers cite several surgical cases in which herbal medicines contributed to complications, ranging from excess bleeding to rejection of transplanted organs.
"We need to specifically ask patients about herbal medication use," said Dr. Jonathan Moss, a professor of anesthesia and critical care and a co-author of the report. Some patients may not consider herbal remedies drugs, and others may consider them medicine but be reluctant to admit to their doctor that they use them.
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. But most pre-operative evaluations take place only a few days before surgery.
That gap led the researchers to search for more specific recommendations. But they found virtually no random, controlled studies that evaluated the effects of prior herbal medicine use on surgical outcomes.
So they conducted their own review of the biological effects of the eight most commonly used herbal remedies - echinacea, ephedra, garlic, ginkgo, ginseng, kava, St. John's wort and valerian -as well as any studies or case reports of problems they caused during or after surgery.
But they caution that their study has many gaps, since the supplements are not as closely regulated or tracked as medicines. And while some manufacturers have made an effort to standardize doses, the potency and purity of herbs can vary widely from maker to maker and even lot to lot, and product labels may not always reflect what's inside a bottle.
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