Safety Information

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St. Johnís Wort  Safety Information


The Medicines Control Agency (MCA), acting on the advice of the Committee on Safety of Medicines (CSM), has advised that St.Johnís 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)


Anticonvulsants (carbamazepine, phenobarbitone, phenytoin)



Oral Contraceptives


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 Ďwhole plantí preparations in much lower doses and without the high concentrations of hypericin found in those standardised extracts. However, if you are currently taking St.Johnís 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.Johnís 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.Johnís 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).


For further information call NHS Direct on 0845 46 47 or the National Institute of Medical Herbalists on 01392 426022

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For your safety I am prohibited from giving specific medical advice to individuals over the internet or telephone so please do not waste your time or mine by emailing or calling me with detailed information about your health problems - I can only undertake face-to-face consultations for what should be obvious reasons. Diagnoses cannot be made remotely, and I am unable to offer any advice or treatment until I am completely satisfied that I know what I'm dealing with!  The herb profiles and treatment suggestions on this website will help enable you to choose which herbs might be appropriate for minor ailments. For more serious or chronic conditions you should seek professional advice. This is particularly important if you are taking medication from your doctor or pharmacist, as some herbs can interact adversely with other drugs. If you would like to have a consultation with a medical herbalist then you should click here  then scroll to 'Professional Organisations' at the bottom of the page to find a qualified practitioner in your area.

Christine Haughton, MA MNIMH MCPP FRSPH

Wold Farm, West Heslerton, Malton, North Yorkshire YO17 8RY, UK

Last updated 27th November 2014     ©Purple Sage Botanicals