Electronic Letters to:
|
|
E-letters: Electronic letters published:
-
![[Read eLetter]](/icons/misc/sectionDOWN.gif)
No characterisation of the extract and questionable in-vivo correlation.
- Beat Meier, Waedenswil, Switzerland (12 August 2005)
|
|
|||
|
Beat Meier, Docent for Phytopharmacy University of Applied Sciences, Waedenswil, Switzerland
Send e-letter to journal:
|
The clinical relevance of the publication is very questionable. In Germany and Switzerland herbal medicinal products made from ethanolic or isopropanolic extracts of the root of Cimicifuga racemosa have been one the market for a long time. In both countries, where a very efficient pharmacovigilance system is available, herbal medicinal products are accepted as medicines by the local authorities (Bundesamt fE Arzneimittel in Germany, Swissmedic in Switzerland). Up to now clinical interactions of Cimicifuga-extracts with other drugs were not reported. This is in agreement with a new publication of Gurley et al. (Clinical Pharmacology & Therapeutics 2005, 77: 415-26). The authors describe in-vivo studies with 12 volunteers where CYP3A4 was not influenced by a black cohosh product. Only a weak inhibition of CYP2D6 was observed. The authors conclude that "the clinical relevancy of this effect remains unclear." Neither Gurley et al. nor Tsukamoto et al. present detailed data concerning the quality of the tested extracts. This is very questionable. Drug-extract ratio, extraction solvent, phytochemical characterisation and -in case of in vivo-studies -the daily dosage of the native extract are indispensable characteristics to compare the tested extracts with European products of well established use. Furthermore, for in-vivo experiments the solubility of the extract samples and their characteristic compounds have to be discussed. Reviewers of articles in the field of herbal medicinal products should be aware of these requirements. Tsukamoto et al. speculate that 40 mg of the unknown black cohosh extract could be estimated to inhibit the metabolism of roughly half a dose of nifedipine. However, the dosage for Cimicifuga racemosa given by the commission E and approved by ESCOP is 40 mg of herbal drug and not of 40 mg of herbal preparation (extract). 40 mg of herbal drug are equivalent to 6.5 mg of native herbal drug preparation, which is the daily dosage (in one or two tablets) in Europe. Compared to ketoconazole the presented IC50-values of Cimicifuga racemosa compounds and extracts are relatively weak. The differences between the extracts and ketoconazole seem to be even more pronounced when the therapeutic dosage of both is compared: 6.5 mg of native extracts of Cimicifuga racemosa versus 200 mg of ketoconazol. As long as no relevant clinical interactions of black cohosh preparations with other drugs are observed, the risk of the mentioned European Cimicifuga racemosa products remain very low in practice. Beat Meier, PhD
B. Meier was engaged before his transfer at 1.9.2004 to the University of Applied Science in Waedenswil in the pharmaceutical development of a Black Cohosh preparation of Zeller AG, Herbal Medicinal Products. CH-8590 Romanshorn. |
|||