Credit: CDC
A new study indicates that a fair share of patients may be mixing the herbal supplement St. John’s wort with prescribed medications, which can have dangerous results.
St. John’s wort can reduce the concentration of numerous drugs in the body, including anticoagulants and chemotherapeutic agents. And this can result in impaired effectiveness and treatment failure.
But the supplement can also interact with medications to produce serious adverse events.
“Patients may have a false sense of safety with so-called ‘natural’ treatments like St. John’s wort,” said study author Sarah Taylor, MD, of Wake Forest Baptist Medical Center in Winston-Salem, North Carolina.
“And it is crucial for physicians to know the dangers of ‘natural’ treatments and to communicate the risks to patients effectively.”
Dr Taylor and her colleagues investigated the use of St. John’s wort and reported their findings in The Journal of Alternative and Complementary Medicine.
To determine how often the supplement was being prescribed or taken with other medications, the researchers conducted a retrospective analysis of nationally representative data collected by the National Ambulatory Medical Care Survey from 1993 to 2010.
The team found the use of St. John’s wort in potentially harmful combinations in 28% of the cases reviewed. The drugs involved were warfarin, selective serotonin reuptake inhibitors, benzodiazepines, statins, verapamil, digoxin, and oral contraceptives.
Possible drug interactions include serotonin syndrome (a potentially fatal condition that causes high levels of the chemical serotonin to accumulate in the body), heart disease due to impaired efficacy of blood pressure medications, or unplanned pregnancy due to contraceptive failure, Dr Taylor said.
A key limitation of this study is that only medications recorded by the physician were analyzed. And Dr Taylor said the rate of St. John’s wort interactions may actually be underestimated because the database did not include patients who were using St. John’s wort but did not tell their doctor.
“Labeling requirements for helpful supplements such as St. John’s wort need to provide appropriate cautions and risk information,” Dr Taylor said, adding that France has banned the use of St. John’s wort products, and several other countries, including Japan, the UK, and Canada, are in the process of including drug-herb interaction warnings on St. John’s wort products.
“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.”
