Licorice Compound Potential Treatment for SARS

Glycyrrhizin, a substance that occurs naturally in licorice, is a potent inhibitor of the virus that causes severe acute respiratory syndrome (SARS), according to a report in Lancet (2003;361:2045–6). Although this study was done in the test tube, rather than in people, the results represent a potentially important breakthrough in the battle against this serious new epidemic.

SARS is a highly contagious, severe viral infection that has recently been reported in China, Canada, Europe, and elsewhere. The symptoms of SARS resemble those of influenza; however, serious breathing difficulties may develop, culminating in death in approximately 10% of cases. First reported late last year, nearly 800 people have died from SARS. As of this writing, no effective treatment has been identified, and public health officials have instituted quarantines in areas where infections are occurring.

In the new study, the effects of glycyrrhizin and four commercially available antiviral drugs were tested against viruses isolated from two patients with SARS. Glycyrrhizin and two of the drugs were found to inhibit replication of the virus. Both of the drugs also damaged the virus-infected cells, however, when present at concentrations only 6 to 12 times greater than the virus-inhibiting concentration. Glycyrrhizin, on the other hand, was nontoxic to the virus-infected cells, even at concentrations up to 67 times greater than the virus-inhibiting concentration. These results suggest that glycyrrhizin might turn out to be a safe and effective treatment for SARS.

Glycyrrhizin is available as a prescription medication in Japan. When administered intravenously, this licorice-derived compound has been found to be beneficial in the treatment of acute and chronic viral hepatitis. Preliminary studies suggest that it also may be helpful for people infected with HIV, the virus that causes AIDS.

When administered in large amounts, glycyrrhizin can cause adverse effects, including high blood pressure, potassium depletion, and severe muscle damage; such side effects have occasionally been reported after long-term ingestion of excessive quantities of licorice. Because of these potential side effects, glycyrrhizin should be used only under the supervision of a doctor. The Japanese product, which has not been approved by the U.S. Food and Drug Administration, appears to cause very few side effects. This product, known as Stronger Neo-Minophagen C (SNMC), also contains the amino acid glycine, which is believed to prevent many of the adverse effects of glycyrrhizin.

Because of the apparent safety of glycyrrhizin and the serious nature of the SARS epidemic, clinical trials using this licorice compound are urgently needed.

Alan R. Gaby, MD, an expert in nutritional therapies, testified to the White House Commission on CAM upon request in December 2001. Dr. Gaby served as a member of the Ad-Hoc Advisory Panel of the National Institutes of Health Office of Alternative Medicine. He is the author of Preventing and Reversing Osteoporosis (Prima, 1994), and co-author of The Natural Pharmacy, 2nd Edition (Healthnotes, Prima, 1999), the A–Z Guide to Drug-Herb-Vitamin Interactions (Healthnotes, Prima, 1999), Clinical Essentials Volume 1 and 2 (Healthnotes, 2000), and The Patient’s Book of Natural Healing (Prima, 1999). A former professor at Bastyr University of Natural Health Sciences, in Kenmore, WA, where he served as the Endowed Professor of Nutrition, Dr. Gaby is the Chief Medical Editor for Healthnotes, Inc.

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