Feverfew products
CMAJ 1997;157:510
See response from: K. Cottrell
The article "Herbal products begin to attract the attention of brand-name drug companies" (CMAJ 1996;155:216-9 [full text / en bref]), by Kate Cottrell, contains some errors.
The Health Protection Branch (HPB) of Health Canada regulates botanical products under its Food and Drug directorates. If a product is classified as a drug, usually after a manufacturer makes a therapeutic claim or the Drug Directorate decides it has pharmacologic activity, it must have a drug identification number (DIN) in order to be marketed legally. However, many products with widely recognized pharmacologic activity are sold in Canada with and without a DIN.
Tanacet, a feverfew-based product highlighted in the article, is correctly identified as the first modern herbal product accorded a DIN for a specific therapeutic application based on orthodox clinical data. However, the article states incorrectly that a DIN was needed "because it exceeds an HPB-specified level of parthenolide, the active ingredient." The DIN is based entirely on the therapeutic claim. As an employee of the Drugs Directorate for 20 years and the official spokesperson on herbal science, I was instrumental in establishing, along with Dr. Stan Heptinstall of the University of Nottingham's Queen's Medical Centre, the criterion of a minimum content of 0.2% parthenolide for feverfew leaf's sesquiterpene lactones in inhibiting in vitro release of serotonin from blood platelets. This theory of the mechanism of migraine is simply the best hypothesis so far and has not been demonstrated to be relevant to the prevention of migraine.
Further, the assertion that "before launching the product, McNeil identified which species of feverfew had the highest level of parthenolide" is false. McNeil was not involved in the DIN application, which was obtained by Herbal Laboratories in the UK. Although 34 species in 2 plant families have been identified as containing parthenolide, so far only feverfew (Tanacetum parthenium, dried leaf) has been clinically tested.
Finally, the statement that "Life Brand . . . products are tested to ensure standardization and shelf life of the active ingredients" displays a lack of appreciation of 2 major areas of contention in herbal medicine science today. The active constituents of a herbal medication that are responsible for its pharmacologic effects are rarely known to the degree that doseresponse relations can be meaningfully established, making expiry dates a problem. The standardization claimed by many manufacturers often has more bearing on quality control and batch-to-batch consistency than on intensity and reliability of effect and is the subject of intense debate within the industry and certain regulatory agencies.
Dennis V.C. Awang, PhD, FCIC
President
MediPlant Consulting Services
Ottawa, Ont.
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