The reddish substance in the flowers of St. John’s wort contains numerous biologically active compounds, including hypericin and hyperforin.
(See also Overview of Dietary Supplements.)
Claims for St. John’s Wort
People take St. John’s wort mostly to relieve symptoms of mild to moderate depression.
St. John’s wort also has been used in the treatment of skin disorders, including psoriasis, and attention-deficit/hyperactivity disorder (ADHD) in children.
There are claims that St. John’s wort can inhibit HIV, the virus that causes AIDS. However, it interferes with the effects of many of the medications that are more effective for HIV infection.
Evidence for St. John’s Wort
The effectiveness of St. John’s wort in treating ADHD or skin disorders has not been well-studied and is considered unproved.
Side Effects of St. John’s Wort
St. John’s wort may increase sensitivity to sunlight. Other side effects include dry mouth, constipation, fatigue, confusion, and, in people with bipolar disorder, mania.
During pregnancy, St. John’s wort increases muscle tone in the uterus and thus may increase the risk of a miscarriage.
Drug Interactions with St. John’s Wort
One of the larger problems with St. John’s wort is that it interacts negatively with a number of medications people take (see table ). These interactions may lead to toxic reactions or ineffectiveness of the medication.
Some Drug Interactions With St. John's Wort
Affected Drugs | Interaction |
|---|---|
Benzodiazepines | St. John’s wort may reduce the effectiveness of these medications in reducing anxiety and may increase the risk of side effects such as drowsiness. |
St. John’s wort may reduce blood levels of factor Xa inhibitors. | |
Iron | St. John’s wort may reduce iron absorption. |
Monoamine oxidase inhibitors (MAOIs) | St. John’s wort may intensify the effects of MAOIs, possibly causing very high blood pressure that requires emergency treatment. |
Nonnucleoside reverse transcriptase inhibitors | St. John’s wort increases the metabolism of these medications, reducing their effectiveness. |
Oral contraceptives | St. John’s wort increases the metabolism of oral contraceptives, reducing their effectiveness. |
When taken with these medications, St. John’s wort may increase the risk of sun sensitivity. | |
St. John’s wort may reduce blood levels of protease inhibitors, making them less effective. | |
St. John’s wort may intensify the effects of these medications. | |
Tricyclic antidepressants | St. John’s wort may decrease the effects of these medications. |
Recommendations for St. John’s Wort
St. John’s wort may help ease symptoms of anxiety and mild to moderate depression. The American College of Physicians has stated that it may help symptoms of mild to moderate depression and may cause fewer side effects than conventional antidepressants.
However, St. John’s wort interacts negatively with many medications people take, so they should check with their doctor before taking it. Some countries have banned its use due to the numerous drug interactions.
Pregnant women and people taking medications for HIV infection should not take St. John’s wort.
More Information
The following English-language resource may be useful. Please note that THE MANUAL is not responsible for the content of this resource.
National Institutes of Health's National Center for Complementary and Integrative Health: St. John’s Wort
