SAN FRANCISCO—Herbal products and other so-called nutritional supplements have become increasingly popular in the United States as an alternative to conventional medicines. “Many people assume that herbal products are safer because they are natural, but unfortunately, this is not always the case,” said Kent R. Olson, MD, at the Society of Critical Care Medicine’s (SCCM’s) 30th International Educational and Scientific Symposium.[1]

In addition, many patients fail to recognize that herbal products can interact with conventional medicines, at times with life-threatening consequences. Among the problems that may arise—and require intensive care—are severe arrhythmias, seizures, and coagulopathies. Dr. Olson reviewed some of the more dangerous herbal products and some of the most severe interactions between herbal ingredients and conventional medicines at the SCCM meeting.

“One of the things that has led to the explosion in the use of these products—and in their advertising—was the 1994 Dietary Supplement Health and Education Act that loosened the FDA’s [Food and Drug Administration’s] regulation of these products,” said Dr. Olson, Medical Director of the California Poison Control System, San Francisco Division, and Clinical Professor of Medicine and Pharmacy at the University of California, San Francisco. “As a result, it has been more difficult to regulate the quality of products. Sometimes, the product is inaccurately or incompletely labeled, or it contains adulterants. Even with herbal products that are properly labeled, the concentration of the active ingredient may vary, and therefore dosing may be inconsistent.”

Many products, if used on their own, are safe, and clinical trials have shown that some are effective for specific indications.

But an increasing number of case reports and other studies indicate that some ingredients in herbal products can produce severe, sometimes lethal, reactions. For example, ephedra, or ma huang (Ephedra sinica)—found in numerous weight-loss and energy-boosting products—can cause hypertension, arrhythmias, seizures, and even death.

Coltsfoot (Tussilago farfara) and comfrey (Symphytum officinale) are two of several herbal products that contain pyrrolizidine alkaloids, which can cause hepatic veno–occlusive disease. (Coltsfoot is believed to alleviate some respiratory problems; comfrey is considered an anti-inflammatory agent.) Comfrey also can be mistaken for foxglove (Digitalis purpurea); digitalis overdose can occur if a patient ingests the wrong herb.

Other plants that contain cardiac glycosides include oleander (Nerium odoratum), lily-of-the-valley (Convallaria majalis), and squill (Drimia maritima). All three of these plants have been traditionally used for cardiac disorders, but all three can cause severe arrhythmias, among other problems.

Monkshood (aconite, Aconitum napellus), which is used in Chinese medicine as a pain reliever and antirheumatic, can cause hypotension and lethal ventricular arrhythmias. Water hemlock (Cicuta maculata) contains circutoxin, a potent convulsant.

Even many commonly used herbal products are dangerous if used concomitantly with conventional medicines. Ginseng (Panax ginseng), widely used for its purported physical and mental effects, has been implicated as a cause of decreased responsiveness to warfarin. In contrast, garlic (Allium sativum) and ginkgo (Ginkgo biloba), which are believed to boost mental acuity, may promote bleeding in patients taking warfarin.

St. John’s wort (Hypericum perforatum), marketed as a dietary supplement for mild depression, has been found to decrease the bioavailability of a number of drugs, including warfarin, indinavir, and cyclosporine. Furthermore, it should not be used with prescription antidepressants, including the selective serotonin reuptake inhibitors and monoamine oxidase inhibitors; combined use may produce the serotonin syndrome. The combination of ginseng and an antidepressant may result in mania.

In addition, patients using Siberian ginseng (Eleutherococcus senticosus, touted for its ability to combat fatigue and improve concentration) have been found to have increased digoxin levels, which may increase their risk of toxicity. Plantain (Plantago laceolata), an ingredient of some herbal cold remedies, has also been reported to increase digoxin levels.

There have been reports of patients becoming addicted to products containing gamma-hydroxybutyrate (GHB), a chemical often touted to promote body building and enhance sexual responsiveness, among other things. Furthermore, said Dr. Olson, “an increasing number of patients are being seen in the ICU [intensive care unit] with GHB-withdrawal symptoms that mimic a severe alcohol withdrawal syndrome.”

To prevent these adverse events, physicians need to be aware of any products their patients are taking. Unfortunately, “patients often don’t want to admit to their doctor that they are taking herbal medicines or they may not realize that it is important,” pointed out Dr. Olson. Nonetheless, “physicians should ask all patients about the use of these products.”

—Deborah L. O’Connor