Information for Consumers

Published: April 2000

St. John's Wort and Prescribed Medicines

Read this information if you are taking St John's wort together with any medicine prescribed for you by your doctor. If you are taking St John's wort and are not taking any prescribed medicines there is no need to stop taking St John's wort or see your doctor.

Preparations containing St John's wort (Hypericum perforatum) are used for a variety of conditions including the symptoms of depression. Taken at the recommended dose, St John's wort has few adverse effects (for example nausea, rash). However, it can interfere with the action of some other medicines making them less effective. It does this by causing enzymes in the liver and gut to breakdown some medicines faster than usual.

Contact your doctor immediately if you are taking St John's wort and notice signs or symptoms indicating that your medicine is less effective than usual, for example, less control of seizures with antiepilepsy medication.

Even if you do not notice any change in your health, but are taking a prescribed medicine and St John's wort, you should see your doctor. The following table indicates when you should see your doctor:

Medicines Consult your doctor
  • immunosupressants for transplant rejection eg. cyclosporin (Neoral); tacrolimus (Prograf)
  • HIV treatments eg. indinavir (Crixivan); nelfinavir (Viracept); ritonavir (Norvir); saquinavir (Fortovase, Invirase); nevirapine (Viramune), efavirenz (Stocrin)
  • carbamazepine (Tegretol, Teril); phenobarbitone; phenytoin (Dilantin) for epilepsy
  • digoxin (Lanoxin) for heart disease
  • warfarin (Marevan, Coumadin) for blood thinning
as soon as possible
  • sumatriptan (Imigran); rizatriptan (Maxalt) for migraine
  • some antidepressants eg. citralopram (Cipramil); fluoxetine (Prozac, Fluox, Lovan, Plinzene); fluvoxamine (Luvox); paroxetine (Aropax); sertraline (Zoloft); nefazodone(Serzone)
in the near future
  • oral contraceptives
  • theophylline (Nuelin, Theo-Dur) for asthma
  • any other prescribed medicine
when you get your next prescription


Your doctor may decide that you should stop St John's wort, or that the effectiveness of the prescribed medicine should be monitored, or that it is unlikely that St John's wort will be interfering. If you are advised to stop St John's wort discuss other alternative treatment options with your doctor.

Do not stop St John's wort without consulting your doctor, because your prescribed medicine may become too potent, and the dose may need to be adjusted.

When discussing treatment options, always tell your healthcare professional if you are taking any other medicines (including any that you buy without a prescription from a pharmacy, supermarket or health food shop) or complementary healthcare product.

Information for healthcare professionals is available on this site.  This information was sent to all general practitioners, selected specialists, community and hospital pharmacies, and complementary healthcare practitioners and retailers on 31 March 2000.