St. john's wort
St. john's wort

Background

St. John's wort is a plant native to Europe with yellow, star-shaped flowers. It's often used for depression but can cause serious interactions with some drugs.

St. John's wort is named after John the Baptist. The plant usually begins to flower around the 24th of June, the feast day of St. John the Baptist. It contains many chemicals that act on messengers in the brain that regulate mood.

People most commonly use St. John's wort for depression and mood disorders. There is some strong scientific evidence that it is effective for mild to moderate depression. St. John's wort is also used for symptoms of menopause and many other conditions, but there is no good scientific evidence to support most of these other uses.

St. John's wort is available in dietary supplements in the US. But France has banned its use in products because of drug interaction concerns. In other countries, St. John's wort is only available with a prescription.
When taken by mouth: St. John's wort is likely safe when used in doses up to 900 mg daily for up to 12 weeks. It can cause some side effects such as diarrhea, dizziness, trouble sleeping, restlessness, and skin tingling. St. John's wort interacts with many drugs. Let your healthcare provider know if you want to take St. John's wort.

St. John's wort is possibly unsafe when taken in large doses. It might cause severe skin reactions after sun exposure. Wear sun block outside, especially if you are light-skinned.

When applied to the skin: St. John's wort is possibly safe when it is applied to the skin once a week for four weeks. However, St. John's wort might cause severe skin reactions after sun exposure.

Special Precautions & Warnings:

Pregnancy: St. John's wort is possibly unsafe when taken by mouth during pregnancy. Taking St. John's wort while pregnant might cause birth defects in infants. Until more is known, don't use St. John's wort when pregnant.

Breast-feeding: St. John's wort is possibly unsafe when taken by mouth while breast-feeding. Infants can experience colic, drowsiness, and fussiness. Until more is known, don't use St. John's wort when breast-feeding.

Children: St. John's work is possibly safe when taken by mouth for up to 8 weeks in children 6-17 years-old.

Alzheimer disease: St. John's wort might make dementia worse in people with Alzheimer disease.

Bipolar disorder: St. John's wort can bring on mania in people with bipolar disorder, and can also speed up the cycling between depression and mania.

Depression: In people with major depression, St. John's wort might bring on mania, which can involve impulsive behavior.

Schizophrenia: St. John's wort might bring on psychosis in some people with schizophrenia.

Surgery: St. John's wort might affect serotonin levels in the brain, which could interfere with surgical procedures. Also, in people who have used St. John's wort, using anesthesia may lead to serious heart complications during surgery. Stop using St. John's wort at least two weeks before a scheduled surgery.

Effectiveness

NatMed Pro rates effectiveness based on scientific evidence according to the following scale: Effective, Likely Effective, Possibly Effective, Possibly Ineffective, Likely Ineffective, Ineffective, and Insufficient Evidence to Rate.
Likely effective Effectiveness definitions
  • Depression. Taking specific St. John's wort extracts by mouth is effective for mild or moderate depression. Certain St. John's wort products might work as well as some prescription drugs and might cause fewer side effects.
Possibly effective Effectiveness definitions
  • Symptoms of menopause. Taking St. John's wort by mouth seems to help reduce hot flashes and other symptoms of menopause.
  • Emotional distress caused by extreme focus on a physical symptom (somatic symptom disorder). Taking a specific St. John's wort product (LI 160, Lichtwer Pharma) seems to reduce symptoms of this condition.
Likely ineffective Effectiveness definitions
Possibly ineffective Effectiveness definitions
  • Burning pain in the mouth. Taking St. John's wort by mouth doesn't seem to reduce pain from burning mouth syndrome.
  • Swelling (inflammation) of the liver caused by the hepatitis C virus (hepatitis C). Taking hypericin, a chemical in St. John's wort, by mouth, doesn't seem to be effective for hepatitis C infection.
  • HIV/AIDS. Taking hypericin, a chemical in St. John's wort, by mouth or by IV, doesn't seem to be effective for treating HIV in adults. IV products can only be given by a healthcare provider.
  • A long-term disorder of the large intestines that causes stomach pain (irritable bowel syndrome or IBS). Taking St. John's wort by mouth doesn't seem to reduce symptoms of IBS.
  • Nerve damage in the hands and feet (peripheral neuropathy). Taking St. John's wort by mouth does not seem to relieve nerve pain due to diabetes or other causes.
  • A type of anxiety marked by fear in some or all social settings (social anxiety disorder). Taking St. John's wort by mouth does not seem to improve social anxiety.
There is interest in using St. John's wort for a number of other purposes, but there isn't enough reliable information to say whether it might be helpful.
Insufficient evidence Effectiveness definitions

Dosing & administration

Talk to your healthcare provider before taking St. John's wort. It can interact with many different drugs.

St. John's wort extract is most commonly used by adults in doses of 600-900 mg by mouth daily, taken in 2-3 divided doses, for up to 12 weeks. St. John's wort is also available in ointments, creams, and gels. Speak with a healthcare provider to find out what type of product and dose might be best for a specific condition.

Interactions with pharmaceuticals

Alprazolam (Xanax)

Interaction Rating=Major Do not take this combination.

The body breaks down alprazolam to get rid of it. St. John's wort can increase how fast the body gets rid of alprazolam. This might decrease the effects of alprazolam.

Ambrisentan (Letairis)

Interaction Rating=Minor Be watchful with this combination.

The body breaks down ambrisentan to get rid of it. St. John's wort might increase how quickly the body gets rid of ambrisentan. But this effect is probably not a big concern.

Aminolevulinic acid

Interaction Rating=Moderate Be cautious with this combination.

Aminolevulinic acid can make the skin sensitive to sunlight. St. John's wort might also increase sensitivity to sunlight. Taking St. John's wort along with aminolevulinic acid might increase the chances of sunburn, blistering or rashes on areas of skin exposed to sunlight. Be sure to wear sunblock and protective clothing when spending time in the sun.

Birth control pills (Contraceptive drugs)

Interaction Rating=Major Do not take this combination.

Some birth control pills contain estrogen. The body breaks down the estrogen in birth control pills to get rid of it. St. John's wort might increase the breakdown of estrogen. Taking St. John's wort along with birth control pills might decrease the effects of birth control pills. If you take birth control pills along with St. John's wort, use an additional form of birth control such as a condom.

Boceprevir (Victrelis)

Interaction Rating=Minor Be watchful with this combination.

St. John's wort contains a chemical called hypericin. Taking St. John's wort with boceprevir might increase the amount of hypericin in the body. This might increase the effects or side effects of St. John's wort.

Bupropion (Wellbutrin)

Interaction Rating=Moderate Be cautious with this combination.

The body breaks down bupropion to get rid of it. St. John's wort might increase how quickly the body breaks down bupropion. This might decrease the effects of bupropion.

Clopidogrel (Plavix)

Interaction Rating=Moderate Be cautious with this combination.

The body must convert clopidogrel to its active form. Taking St. John's wort increases how quickly the body converts clopidogrel to the active form. This might increase the effects and side effects of clopidogrel, such as bruising and bleeding.

Clozapine (Clozaril)

Interaction Rating=Moderate Be cautious with this combination.

The body breaks down clozapine to get rid of it. St. John's wort might increase how quickly the body breaks down clozapine. This might decrease how well clozapine works.

Cyclosporine (Neoral, Sandimmune)

Interaction Rating=Major Do not take this combination.

The body breaks down cyclosporine to get rid of it. St. John's wort can increase how quickly the body breaks down cyclosporine. This might decrease how well cyclosporine works.

Digoxin (Lanoxin)

Interaction Rating=Major Do not take this combination.

St. John's wort might decrease how much digoxin the body absorbs. By decreasing how much digoxin the body absorbs, St. John's wort might decrease the effects of digoxin.

Docetaxel (Taxotere)

Interaction Rating=Major Do not take this combination.

The body breaks down docetaxel to get rid of it. St. John's wort can increase how quickly the body breaks down docetaxel. This might decrease how well docetaxel works.

Fentanyl

Interaction Rating=Moderate Be cautious with this combination.

The body breaks down fentanyl to get rid of it. St. John's wort might increase how quickly the body gets rid of fentanyl. This might decrease the effects of fentanyl.

Fexofenadine (Allegra)

Interaction Rating=Moderate Be cautious with this combination.

The body breaks down fexofenadine to get rid of it. St. John's wort might decrease how quickly the body gets rid of fexofenadine. This could increase the effects and side effects of fexofenadine.

Finasteride (Proscar, Propecia)

Interaction Rating=Moderate Be cautious with this combination.

The body breaks down finasteride to get rid of it. St. John's wort might increase how quickly the body gets rid of finasteride. Taking St. John's wort along with finasteride might decrease its effects.

Gliclazide (Diamicron, others)

Interaction Rating=Moderate Be cautious with this combination.

The body breaks down gliclazide to get rid of it. St. John's wort might increase how quickly the body gets rid of gliclazide. This might decrease the effects of gliclazide.

Imatinib (Gleevec)

Interaction Rating=Major Do not take this combination.

The body breaks down imatinib to get rid of it. St. John's wort might increase how quickly the body gets rid of imatinib. Taking St. John's wort along with imatinib might decrease the effects of imatinib.

Indinavir (Crixivan)

Interaction Rating=Moderate Be cautious with this combination.

The body breaks down indinavir to get rid of it. St. John's wort might increase how quickly the body breaks down indinavir. This might decrease the effects of indinavir.

Irinotecan (Camptosar)

Interaction Rating=Major Do not take this combination.

The body breaks down irinotecan to get rid of it. St. John's wort might increase how fast the body breaks down irinotecan. This might decrease the effects of irinotecan.

Ivabradine (Corlanor)

Interaction Rating=Moderate Be cautious with this combination.

The body breaks down ivabradine to get rid of it. St. John's wort might increase how fast the body breaks down ivabradine. This might decrease the effects of ivabradine.

Medications changed by the liver (Cytochrome P450 1A2 (CYP1A2) substrates)

Interaction Rating=Moderate Be cautious with this combination.

Some medications are changed and broken down by the liver. St. John's wort might change how quickly the liver breaks down these medications. This could change the effects and side effects of these medications.

Medications changed by the liver (Cytochrome P450 2B6 (CYP2B6) substrates)

Interaction Rating=Moderate Be cautious with this combination.

Some medications are changed and broken down by the liver. St. John's wort might change how quickly the liver breaks down these medications. This could change the effects and side effects of these medications.

Medications changed by the liver (Cytochrome P450 2C19 (CYP2C19) substrates)

Interaction Rating=Moderate Be cautious with this combination.

Some medications are changed and broken down by the liver. St. John's wort might change how quickly the liver breaks down these medications. This could change the effects and side effects of these medications.

Medications changed by the liver (Cytochrome P450 2C9 (CYP2C9) substrates)

Interaction Rating=Moderate Be cautious with this combination.

Some medications are changed and broken down by the liver. St. John's wort might change how quickly the liver breaks down these medications. This could change the effects and side effects of these medications.

Medications changed by the liver (Cytochrome P450 3A4 (CYP3A4) substrates)

Interaction Rating=Major Do not take this combination.

Some medications are changed and broken down by the liver. St. John's wort might change how quickly the liver breaks down these medications. This could change the effects and side effects of these medications.

Medications for HIV/AIDS (Nonnucleoside Reverse Transcriptase Inhibitors (NNRTIs))

Interaction Rating=Major Do not take this combination.

The body breaks down medications used for HIV/AIDS to get rid of them. St. John's wort can increase how quickly the body breaks down these medications. Taking St. John's wort might decrease how well some of these medications work.

Medications for HIV/AIDS (Protease Inhibitors)

Interaction Rating=Major Do not take this combination.

The body breaks down medications used for HIV/AIDS to get rid of them. Taking St. John's wort might increase how quickly the body breaks down these medications. Taking St. John's wort might decrease how well some of these medications work.

Medications moved by pumps in cells (P-Glycoprotein Substrates)

Interaction Rating=Major Do not take this combination.

Some medications are moved in and out of cells by pumps. St. John's wort might change how these pumps work and change how much medication stays in the body. In some cases, this might change the effects and side effects of a medication.

Medications that increase sensitivity to sunlight (Photosensitizing drugs)

Interaction Rating=Moderate Be cautious with this combination.

Some medications might make the skin more sensitive to sunlight. St. John's wort might also make the skin more sensitive to sunlight. Using these products together might increase the risk of sunburn, blistering, or rashes when the skin is exposed to sunlight. Be sure to wear sunblock and protective clothing when spending time in the sun.

Medications used for lowering cholesterol (Statins)

Interaction Rating=Moderate Be cautious with this combination.

The body breaks down some medications to get rid of them. St. John's wort can increase how fast the body gets rid of some medications used for lowering cholesterol. Taking St. John's wort along with these medications might decrease their effects.

Mephenytoin (Mesantoin)

Interaction Rating=Major Do not take this combination.

Mephenytoin is changed and broken down by the body. St. John's wort increases how quickly this medication is broken down by the body. This might decrease the effects of mephenytoin.

Methadone (Dolophine)

Interaction Rating=Moderate Be cautious with this combination.

The body breaks down methadone to get rid of it. St. John's wort might increase how fast the body breaks down methadone. This might decrease the effects of methadone.

Methylphenidate (Concerta, others)

Interaction Rating=Minor Be watchful with this combination.

Taking St. John's wort along with methylphenidate might decrease how well methylphenidate works. But it's not clear if this is a big concern.

Omeprazole (Prilosec)

Interaction Rating=Major Do not take this combination.

The body breaks down omeprazole to get rid of it. St. John's wort can increase how quickly the body breaks down omeprazole. This could decrease the effects of omeprazole.

Oxycodone (Oxycontin)

Interaction Rating=Major Do not take this combination.

The body breaks down oxycodone to get rid of it. St. John's wort might increase how fast the body breaks down oxycodone. This might decrease the effects of oxycodone.

Phenobarbital (Luminal)

Interaction Rating=Major Do not take this combination.

The body breaks down phenobarbital to get rid of it. St. John's wort might increase how quickly the body breaks down phenobarbital. This could decrease how well phenobarbital works and increase the risk of seizures.

Phenprocoumon (Marcoumar, others)

Interaction Rating=Major Do not take this combination.

The body breaks down phenprocoumon to get rid of it. St. John's wort increases how quickly the body breaks down phenprocoumon. This decreases the effects of phenprocoumon.

Phenytoin (Dilantin)

Interaction Rating=Major Do not take this combination.

The body breaks down phenytoin to get rid of it. St. John's wort might increase how quickly the body breaks down phenytoin. This might decrease the effects of phenytoin and increase the possibility of seizures.

Procainamide

Interaction Rating=Moderate Be cautious with this combination.

St. John's wort extract might increase how much procainamide the body absorbs. This could increase the effects and side effects of procainamide. But it's not clear if this is a big concern.

Reserpine (Raudixin, others)

Interaction Rating=Moderate Be cautious with this combination.

Taking St. John's wort might decrease the effects of reserpine.

Rivaroxaban (Xarelto)

Interaction Rating=Major Do not take this combination.

The body breaks down rivaroxaban to get rid of it. St. John's wort can increase how quickly the body breaks down rivaroxaban. This can decrease the effects of rivaroxaban.

Serotonergic drugs

Interaction Rating=Moderate Be cautious with this combination.

St. John's wort might increase a brain chemical called serotonin. Some medications also have this effect. Taking St. John's wort along with these medications might increase serotonin too much. This might cause serious side effects including heart problems, seizures, and vomiting.

Tacrolimus (Prograf)

Interaction Rating=Major Do not take this combination.

The body breaks down tacrolimus to get rid of it. St. John's wort can increase how quickly the body breaks down tacrolimus. This can decrease the effects of tacrolimus.

Theophylline

Interaction Rating=Minor Be watchful with this combination.

The body breaks down theophylline to get rid of it. St. John's wort might increase how quickly the body gets rid of theophylline. Taking St. John's wort along with theophylline might decrease its effects in some people.

Tramadol (Ultram)

Interaction Rating=Moderate Be cautious with this combination.

The body breaks down tramadol to get rid of it. St. John's wort might increase how fast the body breaks down tramadol. This might decrease the effects of tramadol.

Voriconazole (Vfend)

Interaction Rating=Moderate Be cautious with this combination.

The body breaks down voriconazole to get rid of it. St. John's wort might increase how quickly the body gets rid of voriconazole. Taking St. John's wort along with voriconazole might decrease its effects.

Warfarin (Coumadin)

Interaction Rating=Major Do not take this combination.

The body breaks down warfarin to get rid of it. St. John's wort might increase how quickly the body gets rid of warfarin. This might decrease the effects of warfarin and increase the risk of clotting. Be sure to have your blood checked regularly. The dose of your warfarin might need to be changed.

Zolpidem (Ambien)

Interaction Rating=Moderate Be cautious with this combination.

The body breaks down zolpidem to get rid of it. St. John's wort might increase how quickly the body breaks down zolpidem. Taking St. John's wort and taking zolpidem might decrease the effects of zolpidem.

Interactions with herbs & supplements

Herbs and supplements with serotonergic properties: St. John's wort increases a brain chemical called serotonin. Taking it along with other supplements that have this effect might cause serious side effects, including heart problems, seizures, and vomiting. Examples of supplements with this effect include 5-HTP, black seed, L-tryptophan, and SAMe.
Herbs that contain cardiac glycosides: St. John's wort contains chemicals that can affect the heart. These chemicals are called cardiac glycosides. Using it along with other supplements that also contain cardiac glycosides can increase the risk of heart damage. Examples of supplements that contain cardiac glycosides include black hellebore, foxglove, lily-of-the-valley, oleander, and pleurisy root.
Iron: St. John's wort might decrease the absorption of iron.
Red yeast: St. John's wort might increase how quickly the liver breaks down some medications called statins. Red yeast contains chemicals similar to statins. St. John's wort might reduce blood levels of chemicals in red yeast and decrease the effects of red yeast.

Interactions with foods

There are no known interactions with foods.
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This monograph was last reviewed on 16/11/2023 11:00:00 and last updated on 15/12/2020 19:50:49. Monographs are reviewed and/or updated multiple times per month and at least once per year.
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