St. John's wort (Hypericum perforatum) is a flowering shrub native to Europe. It gets its name from the fact that it often blooms on the birthday of the biblical John the Baptist.

The flowers and leaves of St. John's wort contain active ingredients such as hyperforin. St. John's wort is available as a supplement in teas, tablets, liquids and topical preparations.

St. John's wort is often used to treat depression and menopausal symptoms.

Research on St. John's wort use for specific conditions shows:

  • Depression. Several studies support the therapeutic benefit of St. John's wort in treating mild to moderate depression. In fact, some research has shown the supplement to be as effective as several prescription antidepressants. But because St. John's wort causes many drug interactions it might not be an appropriate choice, particularly if you take any prescription drugs.
  • Menopausal symptoms. Some evidence suggests that taking St. John's wort combined with a particular form of black cohosh extract might reduce menopausal symptoms such as hot flashes. The research is less compelling when St. John's wort is used alone.

Caution

St. John's wort can be effective for treating mild to moderate depression. However, the supplement interacts with many medications and can cause serious side effects. Don't use St. John's wort if you take prescription medications.

St. John's wort is generally considered safe when used orally in appropriate doses. However, it can cause:

  • Agitation
  • Anxiety
  • Burning or prickling sensation
  • Dizziness
  • Diarrhea
  • Dry mouth
  • Fatigue
  • Headache
  • Increased sensitivity to sunlight (photosensitivity)
  • Insomnia
  • Irritability
  • Low blood sugar levels (hypoglycemia)
  • Restlessness
  • Stomach discomfort
  • Vivid dreams

There isn't enough information about the safety of using St. John's wort topically.

Don't use St. John's wort during pregnancy or while breast-feeding.

Check with your doctor before using St. John's wort in combination with any prescription drug. Possible interactions include:

  • Alprazolam (Xanax). Taking St. John's wort with this drug used to relieve symptoms of anxiety might decrease the drug's effect.
  • Antidepressants. Taking St. John's wort with antidepressants might increase the risk of the accumulation of high levels of serotonin in your body. Too much serotonin can cause mild to severe side effects. Taking this supplement and an antidepressant requires a doctor's supervision. The supplement can also reduce the effectiveness of nortriptyline (Pamelor). Avoid taking St. John's wort if you're taking a monoamine oxidase inhibitor.
  • Barbiturates. Taking St. John's wort with a drug that acts as a central nervous system depressant (barbiturate) might decrease barbiturate-induced sleep time.
  • Bupropion (Wellbutrin SR). Taking St. John's wort with this antidepressant might decrease the drug's effect.
  • Certain chemotherapy drugs. Taking St. John's wort with irinotecan (Camptosar), Docetaxel (Taxotere) or Imatinib (Gleevec) might reduce the chemotherapy drug's effects.
  • Certain immunosuppressive drugs. Taking St. John's wort with tacrolimus (Prograf) or cyclosporine (Neoral, Sandimmune) might decrease the drug's effect.
  • Certain statins. Taking St. John's wort with simvastatin (Zocor) might reduce the drug's effectiveness.
  • Contraceptive drugs. Use of St. John's wort with contraceptive drugs might result in breakthrough bleeding, irregular bleeding or unplanned pregnancy. An additional or alternative form of birth control might be needed.
  • Cytochrome P450 2C19 (CYP2C19) and cytochrome P450 3A4 (CYP3A4) substrates. Don't take St. John's wort if you're taking a drug affected by these enzymes.
  • Dextromethorphan. Taking St. John's wort with this cough suppressant might increase the risk of the accumulation of high levels of serotonin in your body.
  • Digoxin (Lanoxin). Taking St. John's wort with this heart medication can reduce the drug's effect.
  • Fexofenadine (Allegra). Taking St. John's wort with this antihistamine might cause too much of the drug to build up in your body, worsening usual side effects.
  • Ketamine. Taking St. John's wort with ketamine might reduce the drug's anesthetic effect.
  • Narcotics. Don't take St. John's wort with methadone. Taking St. John's wort with certain narcotics might reduce the drug's effectiveness. Combining the supplement with meperidine (Demerol) might increase the risk of the accumulation of high levels of serotonin in your body. Combining the supplement with narcotics might also increase narcotic-induced sleep time and painkilling effects.
  • Non-nucleoside reverse transcriptase inhibitors. Taking St. John's wort with one of these anti-HIV drugs could reduce the drug's effect.
  • Omeprazole (Prilosec, Zegerid). Don't take St. John's wort with this drug used to treat persistent heartburn. The supplement can reduce the drug's effectiveness.
  • Phenytoin (Dilantin, Phenytek). Taking St. John's wort with this anticonvulsant might result in loss of seizure control.
  • Photosensitizing drugs. Taking St. John's wort with a drug that increases sensitivity to sunlight might increase the risk of a reaction.
  • Protease inhibitors. Taking St. John's wort with this type of antiviral drug can reduce the drug's effectiveness.
  • Triptans. Don't take St. John's wort with these medications used to treat migraines. The supplement might increase the risk of the accumulation of high levels of serotonin in your body. Too much serotonin can cause mild to severe side effects.
  • Voriconazole. Taking St. John's wort with this antifungal drug might reduce the drug's effectiveness.
  • Warfarin (Coumadin, Jantoven). Taking St. John's wort with this drug taken to reduce blood clotting might decrease the drug's effect.
Oct. 13, 2017