St John’s wort

St John's Wort

Let your doctor and pharmacist know if you take St John’s wort.
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St John’s wort is a herbal medicine, also known as Hypericum perforatum. It has been tested in clinical trials and has been shown to be helpful for mild or moderate depression, but not for severe depression.

However, some authorities don’t recommend using it because it has many interactions with other medicines, there are no clear guidelines about what dose is best, and the strength varies between different brands.

St John’s wort interacts with many medicines

St John’s wort can cause dangerous interactions with many other medicines, either by making them less effective or by increasing their side effects.

Do not take St John’s wort with other antidepressants. Make sure you tell your doctor if you are taking St John’s wort, so you can avoid potentially dangerous interactions with your other medicines.

St John’s wort — Interactions*

Effect of St John’s wort on other medicine
All antidepressants
Increases risk of side effects including serotonin syndrome
Oral contraceptives (the pill)
May reduce contraceptive effect
Simvastatin, a cholesterol lowering medicine (Lipex, Ransim, Simvar, Simvasyn, Vytorin, Zimstat, Zocor)
Decreases blood level of simvastatin
Warfarin, a blood thinner (e.g. Coumadin, Marevan)
Reduces blood thinning effect
Clopidogrel, a blood thinner (e.g. Clovix, CoPlavix, DuoCover, Iscover, Piax, Plavix, Redigrel)
Increases bleeding risk
Digoxin, a heart medicine (e.g. Lanoxin, Sigmaxin)
Reduces effect of digoxin
Migraine medicines called triptans, including sumatriptan (Imigran, Sumagran, Suvalan)
Increases risk of side effects
Epilepsy medicines, including carbamazepine (e.g. Tegretol, Teril), phenytoin (e.g. Dilantin) and phenobarbitone
Reduces effect of epilepsy medicines
HIV medicines
Reduces effect of HIV medicine
Alprazolam, an anti-anxiety medicine (e.g. Alprax, Kalma)
Reduces effect of alprazolam
Pethidine and tramadol, pain medicines (e.g. Durotram, Lodam, Tramal, Tramahexal, Tramedo, Zydol)
Increases risk of side effects
Anti-organ rejection medicines, cyclosporin, (Cicloral, Neoral, Sandimmun) and tacrolimus (e.g. Prograf)
Reduces effect of cyclosporin
Theophylline, an asthma medicine (e.g. Nuelin)
Reduces effect of theophylline
Irinotecan, an anti-cancer medicine (e.g. Camptosar, Tecan)
Reduces effect of irinotecan
*This is not a complete list — if you are taking St John’s wort, ask your doctor or pharmacist whether your other medicines interact with it.

Be careful if you switch brands of St John’s wort

Different brands of St John’s wort may have different strengths, so they may have different effects on your mood — and different effects when they interact with your other medicines.

Read more about St John’s wort.

For more information