March 2, 2001
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.