Overview

St. John’s wort, also called Hypericum perforatum, is a flowering shrub native to Europe. St. John’s wort gets its name because it often blooms on the birthday of the biblical John the Baptist.

The flowers and leaves of St. John’s wort have active ingredients such as hyperforin. St. John’s wort can be found as a supplement in teas, tablets, liquids, and preparations that are put on the skin.

People use St. John’s wort to treat depression and symptoms of menopause.

What the research says

Research on St. John’s wort use for specific conditions shows how the supplement may affect those conditions:

• Depression. Many studies have found St. John’s wort to be helpful in treating mild to moderate depression. In fact, some research has shown the supplement to work as well as many prescription antidepressants. It’s unclear whether the supplement helps treat severe depression.

  St. John’s wort interacts with many medicines. So it might not be a suitable choice, especially if you take any prescription medicines.

• Menopause symptoms. Some research suggests that taking St. John’s wort alone or with black cohosh or other herbs might lessen menopause symptoms such as hot flashes.
• Somatic symptom disorder. Some studies have found that St. John’s wort might help treat this condition. Somatic symptom disorder causes severe anxiety about physical symptoms such as pain, weakness, and shortness of breath.

Our take

Caution

St. John’s wort can treat mild to moderate depression. But the supplement interacts with many medicines and can cause serious side effects. Talk with your healthcare professional before taking St. John’s wort if you take any other medicines.

Safety and side effects

When taken by mouth for up to 12 weeks in appropriate doses, St. John’s wort is generally considered safe. But it may cause:

• Anxiety.
• Dizziness.
• Diarrhea, constipation, and upset stomach.
• Dry mouth.

Other side effects may include:

• Tiredness and trouble sleeping.
• Headache.
• Higher sensitivity to sunlight, also called photosensitivity.

There isn’t enough information about the safety of using St. John’s wort on the skin.

Don’t use St. John’s wort during pregnancy or while breastfeeding.

Interactions

The list below includes some known interactions when taking St. John’s wort. But other medicines also may interact with St. John’s wort. Check with your healthcare professional before using St. John’s wort in combination with any other medicines, especially prescription medicines.

• Alprazolam (Xanax). If you take St. John’s wort with this medicine used to ease anxiety symptoms, it might lessen the medicine’s effect.
• Antidepressants. If you take St. John’s wort with antidepressants, it might raise the risk of a buildup of high serotonin levels in the body. Too much serotonin can cause mild to severe side effects. Get supervision from a healthcare professional if you take St. John’s wort and an antidepressant.
• Barbiturates. If St. John’s wort is taken with a medicine that acts as a central nervous system depressant, called a barbiturate, it might lessen the amount of sleep time the medicine causes.
• Bupropion (Wellbutrin SR, Forfivo XL). If you take St. John’s wort with this antidepressant, it might lessen the medicine’s effect.
• Certain chemotherapy medicines that treat cancer. If you take St. John’s wort with irinotecan (Camptosar, Onivyde), docetaxel (Taxotere) or imatinib (Gleevec), it might lessen the chemotherapy medicine’s effects.
• Certain medicines that suppress the immune system. If you take St. John’s wort with tacrolimus (Prograf, Astagraf XL, others) or cyclosporine (Neoral, Sandimmune, others), it might lessen the medicine’s effect.
• Certain statins. If you take St. John’s wort with statins such as atorvastatin, lovastatin, and others, it might lessen how well the statin works.
• Contraceptive medicines. Use of St. John’s wort with medicines used to prevent pregnancy, called contraceptive or birth control medicines, might cause breakthrough bleeding, bleeding that’s not regular or pregnancy that’s not planned. You might need a second or different form of birth control.
• Cytochrome P450 1A2, cytochrome P450 2B6, cytochrome P450 2C19, cytochrome P450 2C9 and cytochrome P450 3A4 substrates. Don’t take St. John’s wort if you’re taking a medicine affected by these enzymes. These enzymes also are called CYP1A2, CYP2B6, CYP2C19, CYP2C9 and CYP3A4.
• Dextromethorphan. If you take St. John’s wort with this cough suppressant, it might raise the risk of the buildup of high serotonin levels in the body.
• Digoxin (Lanoxin). If you take St. John’s wort with this heart medicine, it can lessen the medicine’s effect.
• Fexofenadine (Allegra Allergy). If you take St. John’s wort with this antihistamine, it might cause too much of the medicine to build up in the body. This can worsen usual side effects.
• Ketamine (Ketalar). If you take St. John’s wort with ketamine, it might lessen the medicine’s anesthetic effect.
• Narcotics. Don’t take St. John’s wort with methadone (Methadose). Taking St. John’s wort with some narcotics might lessen how well the medicines work. Mixing the supplement with narcotics also might raise narcotic-induced sleep time and painkilling effects.
• Non-nucleoside reverse transcriptase inhibitors. If you take St. John’s wort with one of these anti-HIV medicines, it could lessen the medicine’s effect.
• Omeprazole (Prilosec). Don’t take St. John’s wort with this medicine used to treat lasting heartburn. The supplement can lessen how well the medicine works.
• Phenytoin (Dilantin, Phenytek). If you take St. John’s wort with this anticonvulsant medicine, the medicine might not work as well to stop seizures.
• Photosensitizing medicines. If you take St. John’s wort with medicine that increases sensitivity to sunlight, called photosensitizing medicine, it might raise the risk of a reaction.
• Protease inhibitors. If you take St. John’s wort with this type of antiviral medicine, it can lessen how well the medicine works.
• Triptans. Don’t take St. John’s wort with these medicines that treat migraines. The supplement might raise the risk of buildup of high serotonin levels in the body. Too much serotonin can cause mild to severe side effects.
• Voriconazole. If you take St. John’s wort with this antifungal medicine, it might lessen how well the medicine works.
• Warfarin (Jantoven). If you take St. John’s wort with this medicine used to reduce blood clotting, it might lessen how well the medicine works.