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St. John’s Wort Safety Information
The Medicines Control Agency (MCA), acting on the advice of the Committee on Safety of Medicines (CSM), has advised that St.John’s Wort (Hypericum perforatum) should not be taken in conjunction with certain prescribed medicines. The CSM has acted cautiously, but it is aware of the under-reporting of adverse reactions and has the duty of protecting public safety. They refer to Hypericum as a safe herbal remedy, but advise that certain precautions should be taken. Their concern is that Hypericum induces liver cytochrome P-450 enzymes, thereby reducing the blood levels of certain drugs and so reducing their effectiveness. The Hypericum/drug interactions currently under investigation include the following:
HIV protease inhibitors (indinavir, nelfinavir, ritonavir, saquinavir)
HIV non-nucleotide reverse transcriptase inhibitors (efavirenz, nevirapine)
Cyclosporin
Anticonvulsants (carbamazepine, phenobarbitone, phenytoin)
Digoxin
Theophylline
Oral Contraceptives
Warfarin
SSRIs (citalopram, fluoxetine, fluvoxamine, paroxetine, sertraline)
Triptans (sumatriptan, naratriptan, rizatriptan, zolmitriptan)
The above list is not exclusive, and further interactions may come to light in the coming months.
The concerns of the CSM are primarily about self-prescribed over-the-counter Hypericum products, and where there have been reports of adverse reactions, standardised preparations which contain large amounts of the constituent hypericin have been involved. Medical herbalists generally use ‘whole plant’ preparations in much lower doses and without the high concentrations of hypericin found in those standardised extracts. However, if you are currently taking St.John’s Wort in any form in conjunction with any GP-prescribed medication or over-the-counter remedy from your pharmacist, please contact your GP, pharmacist or herbalist for advice. DO NOT stop taking St.John’s Wort suddenly without first seeking advice because it may be necessary for your GP to adjust the dose of your prescribed medication.
If you are considering buying St.John’s Wort products, ensure that you first read the MCA information leaflet which is available from retail suppliers of the herb or from Members of the National Institute of Medical Herbalists (NIMH).
ALWAYS TELL YOUR GP OR PHARMACIST IF YOU ARE TAKING ANY HERBAL REMEDIES OR SUPPLEMENTS. SIMILARLY, TELL YOUR HERBALIST IF YOU ARE TAKING ANY PRESCRIBED OR OVER-THE-COUNTER MEDICATION.
For further information call NHS Direct on 0845 46 47 or the National Institute of Medical Herbalists on 01392 426022