Scientists Issue Warning for Mixing St. John's Wort and Some Prescriptions

Researchers at Wake Forest Baptist Medical Center have released a study showing the potential of a dangerous interaction between a common supplement and prescription medication.

In a statement the researchers said taking St. John’s wort (SJW) with some common prescriptions can reduce the concentration of some drugs including contraceptives, blood thinners, chemo therapy drugs and blood pressure pills.

Sarah Taylor, MD, the study’s lead author said the combination can make the needed prescriptions less effective and hamper treatments. “Patients may have a false sense of safety with so-called ‘natural’ treatments like St. John’s wort.”

Taylor, an assistant professor for dermatology, added, “And it is crucial for physicians to know the dangers of ‘natural’ treatments and to communicate the risks to patients effectively.”

The study, which was published in the Journal of Alternative and Complementary Medicine, involved the team looking at data collected by the National Ambulatory Medical Care Survey dating from 1993 to 2010. In all, the use of SJW proved to be potentially harmful when taken in combination with the drugs in 28 percent of the cases the team looked at.

Mixing the prescriptions and the supplement, Taylor’s team reported, can cause serotonin syndrome which can be fatal and causes high levels of serotonin to accumulate in the body. Other potential problems from the weakened medications include heart disease or unplanned pregnancies according to the report.

Looking at the results Taylor said the data was somewhat incomplete because the information only included medications listed for the individual patients by the doctor and could not account for patients who were taking the supplement but had not told their doctors. “Labeling requirements for helpful supplements such as St. John’s wort need to provide appropriate cautions and risk information,” she said.

Products that include SJW have been banned in France according to Taylor who added that other countries including Japan, the United Kingdom and Canada are working to include warning labels in products being sold there. “Doctors also need to be trained to always ask if the patient is taking any supplements, vitamins, minerals or herbs, especially before prescribing any of the common drugs that might interact with St. John’s wort.

Taylor’s team also included co-authors and Wake Forest Baptist colleagues Steven Feldman, MD, and Scott Davis, MA. The study was funded in part by the Center for Dermatology Research at Wake Forest Baptist.