Variations in parthenolide content and daily dose of feverfew products

Variations in the parthenolide content of feverfew products available to consumers were studied. Feverfew products were analyzed for the content of parthenolide, the purported active component. The actual weight of feverfew was determined only in those products containing dried feverfew leaf. The total daily doses of feverfew leaf and parthenolide were calculated by using the instructions on each product label. Parthenolide content was determined by high-performance liquid chromatography. The quantity of feverfew leaf in each capsule was similar to that stated on the label and ranged from 25 to 500 mg. Parthenolide content per dosage form varied 150-fold (from 0.02 to 3.0 mg), while percent parthenolide varied 5.3-fold (from 0.14% to 0.74%). If a person consumed the daily dose recommended on the label, intake of dried feverfew leaf would range from 225 to 2246 mg/day, a 10-fold variation, while intake of parthenolide would range from 0.06 to 9.7 mg/day, a 160-fold variation. Large variations were observed in the parthenolide contents and daily intake as recommended by the labeling in commercial feverfew products.