A report in Wednesday's issue of the Journal of the National Cancer Institute reveals that a popular herbal supplement may interfere with the effectiveness and metabolism of a chemotherapy medication. Consumers using herbal supplements should always research the potential side effects, but this study reminds patients receiving other medical treatments to consult with his or her physician before using any dietary supplements.
Widespread use of St. John's Wort, or hypericum perforatum, began several years ago after reports indicated that the supplement may be just as effective as brand name depression drugs. The recent study, however, found that St. John's Wort increases levels of the enzyme CYP3A4, which inactivates the colorectal cancer drug irinotecan, known as Camptosar.
Led by Dr. Ron Mathijssen and Alex Sparreboom of the Erasmus MC-Daniel den Hoed Cancer Center in The Netherlands, the study followed several patients receiving both Camptosar and St. John's Wort or just the supplement. The researchers discovered that when used in combination with Camptosar, St. John's Wort compromised "overall antitumor activity." The researchers originally revealed their findings to the American Association for Cancer Research in April.