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The Pharmaceutical Journal Vol 264 No 7086 p358
March 4, 2000 Clinical

CSM advice on St John's wort

The Committee on Safety of Medicines (CSM) has announced advice for patients taking St John's wort. This follows reports of interactions between the herb and conventional medicines. The CSM has identified five groups of patients and gives advice for each group (see Panel below).
Professor Alasdair Breckenridge (chairman, CSM) said at a press conference on March 1: "We are advising that anyone who is taking a prescribed medicine should seek the advice of their doctor or pharmacist before taking St John's wort." Describing the five points of advice, he said that it was the first group of patients (those taking cyclosporin, warfarin, digoxin, theophylline or anticonvulsants) who were of particular concern. These patients should not stop taking St John's wort without consulting a doctor or pharmacist because dose adjustment of their medicine might be needed.
Professor Breckenridge said that it was certainly important for women taking oral contraceptives to stop taking St John's wort because continuation could reduce efficacy of the contraceptive. However, because a rise in blood levels of oral contraceptive would not pose a danger to health (in the way that it could for medicines in the first group), it was not necessary for women to seek advice from a doctor before stopping St John's wort.
Professor Breckenridge discussed the mechanisms by which St John's wort interacted with other medicines. It could reduce the effectiveness of certain drugs by increasing their metabolism. This was seen when St John's wort was combined with indinavir, cyclosporin, warfarin, digoxin, theophylline, anticonvulsants and oral contraceptives. Reduced effectiveness was also seen with non-nucleoside reverse transcriptase inhibitors and, in addition to indinavir, was expected to occur with all protease inhibitors, he said.
By another mechanism, St John's wort had synergistic effects with other medicines, said Professor Breckenridge. This was seen with selective serotonin reuptake inhibitors (SSRIs) and triptans. The result was the development of serotonin syndrome, which had symptoms such as lethargy, anxiety and nausea.

CSM advice

  • Users of St John's wort and cyclosporin, warfarin, digoxin, theophylline or anticonvulsants Consult your doctor or pharmacist about stopping St John's wort. Do not stop taking St John's wort first as dose adjustment may be needed
  • Users of St John's wort and anti-HIV medicines Stop taking St John's wort. Consult your doctor in the next week or so to check viral load; there is no need to consult your doctor before stopping St John's wort
  • Users of St John's wort and oral contraceptive pill, or medicines for depression or migraine Stop taking St John's wort; there is no need to consult your doctor
  • Users of St John's wort and any other medicines Speak to your doctor or pharmacist next time you get a prescription or purchase other medicines
  • Future users of St John's wort If you use medicines, do not start taking St John's wort without seeking advice from your doctor or pharmacist

St John's Wort The CSM advice follows the recent publication of reports of problems with St John's wort therapy (PJ, February 19, p285 and January 29, p173). In addition, there have been 14 reports of interactions made via the CSM's yellow card scheme.
Dr June Raine (director of post-licensing, Medicines Control Agency [MCA]) said at the same press conference that the MCA had sent a letter to doctors and pharmacists explaining the CSM's advice. In addition, the MCA would be consulting manufacturers of herbal products and trade associations about placing appropriate warnings on St John's wort products. Changes to product information for those licensed medicines known to interact would also be made. In the long term, the licensing of St John's wort products might be examined but, in the meantime, pressure would be applied in order to get information included with the products, she said.
The MCA says it is currently in dialogue with a number of organisations across the natural health sector about the need to improve the regulation of herbal products. St John's wort is currently unlicensed and there is no statutory requirement to provide specific warning information on such products.
Mr Michael McIntyre (chairman, European Herbal Practitioner Association) said at the press conference that the idea that natural meant 100 per cent safe was "clearly wrong". Herbal medicines were very effective but care was needed when combining medicines.
The Royal Pharmaceutical Society of Great Britain responded by saying that it supported the MCA's decision to publish the safety information for St John's wort. It said: "The Society advocates the establishment of a new category of licensed herbal remedies . . . which meet standards for safety and quality and which are regulated by the MCA." Miss Ann Lewis (secretary and registrar of the Society) said: "The popular public perception of St John's wort is that it is ‘natural' or ‘safe', or both. This may not be the case. Our main concern is that these herbal therapies may not be pure and could be contaminated. The level of active ingredient may also vary between preparations."