The effect of herbal medicines on platelet function: an in vivo experiment and review of the literature.
BACKGROUND
Herbal medicines are used by a considerable number of surgical patients. An increased risk of bleeding, substantiated by anecdotal reports, has been attributed to the use of certain herbs, and numerous in vitro experiments have identified some herbal extracts as platelet inhibitors. The purpose of this investigation was to determine whether standard commercial preparations of commonly used herbal medicines have an effect on platelet function in vivo and, by extension, to provide clinical scientific evidence of the safety of their use in the perioperative period.


METHODS
Five commercially available herbal agents were investigated, including Ginkgo biloba, garlic, Asian ginseng, St. John's wort, and saw palmetto. In a blinded fashion, one of the agents was administered to 10 adult volunteers at the manufacturer's recommended dose for 2 weeks. At the end of the 2-week period, in vivo platelet function was quantified using the PFA-100 assay. After a 2-week "washout" period, the protocol was repeated using a different agent. This 4-week cycle was repeated for each of the five herbal agents, as well as the control agent aspirin.


RESULTS
In vivo platelet function was not affected by the administration of any herbal agent and was markedly inhibited with the administration of aspirin.


CONCLUSIONS
The herbal medicines investigated in this study do not affect platelet function in vivo. Neither this experiment nor a review of the literature supports the concern of perioperative bleeding in users of these herbal medicines.
Beckert
Benjamin W
BW
Columbia, Mo. From the Division of Plastic Surgery and Department of Pathology and Anatomical Sciences, University of Missouri.
Concannon
Matthew J
MJ
Henry
Steven L
SL
Smith
Daniel S
DS
Puckett
Charles L
CL
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001241:Aspirin / Q000494:pharmacology; D001777:Blood Coagulation / Q000187:drug effects*; D001780:Blood Coagulation Tests; D001792:Blood Platelets / Q000187:drug effects*; D005260:Female; D005737:Garlic / Q000009:adverse effects; D020441:Ginkgo biloba / Q000009:adverse effects; D006474:Hemorrhagic Disorders / Q000139:chemically induced; D041743:Herb-Drug Interactions; D006801:Humans; D020902:Hypericum / Q000009:adverse effects; D008297:Male; D008875:Middle Aged; D005894:Panax / Q000009:adverse effects; D010936:Plant Extracts / Q000009:adverse effects / Q000494:pharmacology; D028321:Plant Preparations / Q000009:adverse effects / Q000494:pharmacology*; D010979:Platelet Function Tests; D019106:Postoperative Hemorrhage / Q000139:chemically induced; D028024:Serenoa / Q000009:adverse effects; D016037:Single-Blind Method
D010936:Plant Extracts; D028321:Plant Preparations; C040972:saw palmetto extract; D001241:Aspirin