St John’s wort
Let your doctor and pharmacist know if you take St John’s wort.
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
||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
||Reduces effect of HIV medicine
|Alprazolam, an anti-anxiety medicine (e.g. Alprax, Kalma, Ralozam, Xanax)
||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
- Moses GM, McGuire T. Drug interactions with complementary medicines. Aust Prescr 2010;33:177–80. www.australianprescriber.com/magazine/33/6/177/80 (accessed 9 February 2012).
- Therapeutic Goods Administration. Important interactions between St John's wort (Hypericum perforatum) preparations and prescription medicines. Canberra: TGA, March 2001. www.tga.gov.au/safety/alerts-medicine-stjwort-000313.htm (accessed 26 February 2012).