St. John's wort (Hypericum perforatum) is a common herbal remedy used to treat mild to moderate depression. About a year ago, we reported findings that St. John's wort may interact with certain drugs used to treat HIV infection. The herb does this by interfering with the liver's ability to break down anti-HIV medications, speeding up the body's elimination of at least one drug — indinavir (Crixivan) — and thus lowering levels of indinavir in the blood. This situation could make it easier for HIV to develop resistance to indinavir and other protease inhibitors, which would limit treatment options for PHAs. Now doctors in Amsterdam have found that St. John's wort can also reduce levels of another anti-HIV drug — the NNRTI nevirapine (Viramune) — in PHAs.
The doctors reported data on patients who were taking nevirapine along with two nucleoside analogues for more than one year. During this time, patients were having their blood tested for levels of nevirapine every three months. The doctors noticed that nevirapine levels were less-than-normal in five male patients. The five men were also taking St. John's wort for several months, along with nevirapine. The doctors then compared nevirapine levels in the five men to levels in 176 other PHAs. According to this comparison, St. John's wort significantly reduced levels of nevirapine. Less-than-normal levels of nevirapine in the blood could make it easier for HIV to develop resistance to nevirapine, as well as to other NNRTIs such as efavirenz (Sustiva) and delavirdine (Rescriptor). The Dutch doctors therefore warned that St. John's wort should not be taken by people using nevirapine.
There may be at least two ways in which St. John's wort can reduce levels of nevirapine. First, the herb could decrease absorption of nevirapine in the intestine. Second, St. John's wort could also speed up the rate at which the liver breaks down nevirapine. The findings by the doctors also underscore the importance for patients to tell their doctor(s) about the supplements and herbs they are using. For further information about St. John's wort, please see the CATIE Supplement Sheet at www.catie.ca.
REFERENCES
1. de Maat MMR, Hoetelmans RMW, Math_t RAA, et al. Drug interaction between St John's wort and nevirapine. AIDS 2001;15(3):420-421.
2. Dürr D, Stieger B, Kullak-Ublick GA, et al. St John's wort induces intestinal P-glycoprotein/MDR1 and intestinal and hepatic CYP3A4. Clinical Pharmacology and Therapeutics 2000;68(6):598-604.
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Copyright © 2001 - TreatmentUpdate. Reproduced with permission. Reproduction of this article (other than one copy for personal reference) must be cleared through the Editor, The Canadian AIDS Treatment Information Exchange, 555 Richmond St. West, Suite 505, Box 1104, Toronto, ON, M5V 3B1 • Phone: 416-203-7122 • Toll Free: 1-800-263-1638 • Fax: 416-203-8284 http://www.catie.ca.
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