The reddish substance in the plant’s flowers contains numerous biologically active compounds, including hypericin and hyperforin. (See also Overview of Dietary Supplements.)
Medicinal claims
People take St. John’s wort mostly to relieve symptoms of depression. Study results vary, but there may be a benefit in treating mild to moderate short-term depression. Overall, some studies show St. John’s wort may benefit people with mild to moderate depression and may be as effective as some traditional antidepressants. However, St. John's wort is not effective for major depression.
St. John’s wort has been used in the treatment of skin disorders, including psoriasis, and attention-deficit/hyperactivity disorder (ADHD) in children, but its effectiveness in treating these disorders is unproved.
Possible side effects
St. John’s wort may cause increased sensitivity to sunlight. Other side effects include dry mouth, digestive tract symptoms, fatigue, confusion, and mania (in people with bipolar disorder).
Pregnant women should not take this supplement because it increases muscle tone in the uterus and thus may increase the risk of a miscarriage.
Possible drug interactions
One of the larger problems with St. John’s wort is that it may interact negatively with a number of drugs people take (see table Drug Interactions With St. John's Wort). These interactions may lead to toxic reactions or ineffectiveness of the drug.
Drug Interactions With St. John's Wort
|
Affected Drugs |
Interaction |
|
Benzodiazepines |
St. John’s wort may reduce the effectiveness of these drugs in reducing anxiety and may increase the risk of side effects such as drowsiness. |
|
Cyclosporine |
St. John’s wort may reduce blood levels of cyclosporine, making it less effective, with potentially dangerous results (such as rejection of an organ transplant). |
|
Digoxin |
St. John’s wort may reduce blood levels of digoxin, making it less effective, with potentially dangerous results. |
|
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 drugs, reducing their effectiveness. |
|
Oral contraceptives |
St. John’s wort increases the metabolism of these drugs, reducing their effectiveness. |
|
Omeprazole |
St. John’s wort decreases serum concentrations of omeprazole, reducing its effectiveness. |
|
Photosensitizing drugs (such as amiodarone, naproxen, sulfonylureas [such as glipizide], and sulfonamide antibiotics) |
When taken with these drugs, St. John’s wort may increase the risk of sun sensitivity. |
|
Protease inhibitors (such as indinavir or saquinavir), which are used to treat human immunodeficiency virus [HIV] infection |
St. John’s wort may reduce blood levels of protease inhibitors, making them less effective. |
|
Selective serotonin reuptake inhibitors (SSRIs, such as fluoxetine, paroxetine, and sertraline) |
St. John’s wort may intensify the effects of these drugs. |
|
Tricyclic antidepressants |
St. John’s wort may decrease the effects of these drugs. |
|
Warfarin |
St. John’s wort may reduce blood levels of warfarin, making it less effective and clot formation more likely. |
More Information
The following is an English-language resource that may be useful. Please note that THE MANUAL is not responsible for the content of this resource.
- National Institutes of Health (NIH), National Center for Complementary and Integrative Health: General information on the use of St. John’s wort as a dietary supplement
Drugs Mentioned In This Article
| Generic Name | Select Brand Names |
|---|---|
| Cyclosporine | NEORAL, SANDIMMUNE |
| sertraline | ZOLOFT |
| saquinavir | INVIRASE |
| amiodarone | CORDARONE |
| Omeprazole | PRILOSEC |
| paroxetine | PAXIL |
| fluoxetine | PROZAC, SARAFEM |
| glipizide | GLUCOTROL |
| indinavir | CRIXIVAN |
| naproxen | ALEVE, NAPROSYN |
| Warfarin | COUMADIN |
| Digoxin | LANOXIN |
