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PJ Online | Articles | March FACT: is there an interaction between ginseng and warfarin?

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PJ Online homeThe Pharmaceutical Journal
Vol 274 No 7342 p370
26 March 2005

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March FACT: is there an interaction between ginseng and warfarin?

Research published in the March issue of Focus on Alternative and Complementary Therapies is highlighted by Natalie Lane

Natalie Lane is production editor, journals, with the Pharmaceutical Press

Focus on Alternative and Complementary Therapies

What is FACT?

Focus on Alternative and Complementary Therapies (FACT), edited by Edzard Ernst (Laing Chair in Complementary Medicine, Peninsula Medical School, Universities of Exeter and Plymouth) is an evidence-based journal that is a single point of reference for current information on complementary and alternative medicine (CAM) from around the world. Current literature is summarised and commented on by members of the FACT international editorial board, reviewing topics as diverse as herbal medicines, vitamins, minerals and supplements, homoeopathy, acupuncture and manipulative therapies, and giving readers a concise and objective view of the value of such therapies currently available. FACT also contains news, short reports, focus articles and debates on CAM. The full text of FACT is available by subscription.

For further information visit

To compare Crocus sativus L. (saffron) with imipramine in mild to moderate depression, a study of 30 adult outpatients was carried out in Tehran, Iran. Assessment of the patients was by the Hamilton Rating Scale for Depression (HAM-D) and either C sativus or imipramine was administered but with no placebo control. The authors’ conclusion found that C sativus 10mg demonstrated efficacy in patients with mild to moderate depression, perhaps similar to imipramine 100mg. However, no HAM-D scores were provided and results were displayed graphically.

FACT comments that this is possibly the first published study examining efficacy of C sativus for depression but notes the need for well-designed studies looking into effective safe agents. FACT highlights that this study had many methodological flaws, primarily that it was conducted over a short period with a small number of patients, no placebo controls and no dose finding for either agent. There was particular concern about this since the C sativus dose was based on animal studies. It was also noted that the C sativus product was prepared in-house without verification of its content. FACT suggests that, had the comparator been a first-line antidepressant such as a selective serotonin reuptake inhibitor, there would have been benefit. FACT comments that this study provides useful data but its methodological flaws prevent widespread generalisation and further research is required.

Ginseng and warfarin interaction?

A four-week study of 20 healthy subjects looked at interactions between Panax quinquefolius L. (American ginseng) and warfarin. The subjects received warfarin for three days during weeks 1 and 4. Beginning in week 2, patients were randomly given P quinquefolius or placebo for three weeks. The study monitored the change in peak international normalised ratio (INR) and plasma warfarin levels, and noted that the peak INR of those subjects taking P quinquefolius significantly decreased after two weeks compared with those taking placebo. Also, the INR area under the curve (AUC), peak plasma warfarin level and warfarin AUC were significantly reduced. Although the authors acknowledged the limitations of using healthy patients in this study, they concluded that P quinquefolius reduces the warfarin anticoagulant effect and that doctors should ask their patients about ginseng use if prescribing warfarin.

FACT recognises that there are many concerns about the risks of herb and drug interactions and little evidence to provide medical advice. It highlights that this study carefully addresses the issues of the identification and characteristics of P quinquefolius when other studies on ginseng have had problems of poor identification. However, there are chemical variations within a single species and between manufactured products that can limit the transferability of results, and FACT queries the quality of the P quinquefolius used compared with products available on the market. Although the use of healthy patients and the accompanying limitations of this are acknowledged, FACT comments that this does not detract from the main message of the article — that doctors should ask patients about their use of P quinquefolius when prescribing warfarin and should discuss whether patients plan to start or stop P quinquefolius when warfarin levels have stabilised. FACT also notes that although this study is relevant solely to P quinquefolius, an overall message is that doctors should discuss with their patients the use of any herbal products, especially when drugs of a low therapeutic index are prescribed.

Can antioxidants prevent cancer?

To establish whether antioxidant supplements reduce the incidence of gastrointestinal cancer and mortality researchers identified 14 high-quality randomised trials. Neither the fixed-effect nor random-effect meta-analyses showed any effects of supplementation with the stated antioxidants compared with placebo. The researchers could not find evidence that antioxidant supplements prevented gastrointestinal cancers and supplements appeared to increase overall mortality. The exceptions were four trials in which selenium showed a significant beneficial effect and the researchers suggest that this should be studied further.

FACT observes that hypotheses and leads provided by associations of antioxidant levels and outcomes cannot replace the data of prospective clinical trials. The commentary discusses how the administration of antioxidants can have effects on cell metabolism and proliferation, unrelated to their antioxidant properties. In addition, the combinations of antioxidants are likely to interact and counteract any beneficial effects. The administration of an antioxidant in one individual may have a different biochemical effect to supplementation in another. The use of individual studies — albeit using the gold standard Cochrane analytical methodology and taking into account selection or publication bias — is ultimately based on the quality of data from the analysed studies. Such flaws prevent the absolute conclusion that antioxidants have no role in preventing gastrointestinal cancers. FACT says that the results of the meta-analysis provide a broad perspective but, without detailed information, conclusions cannot be drawn about whether specific antioxidants at determined doses would benefit selected individuals. Until better evidence is received concerning the role of supplementary antioxidants in select situations, FACT proposes proven general lifestyle changes for the general population.

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Citation: The Pharmaceutical Journal URI: 20014288

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