Extracts of Petasites hybridus are prepared from the rhizomes, roots, and leaves. The main active constituents are two sesquiterpenes, petasin and isopetasin. Petasin is responsible for the antispasmodic properties of the plant by reducing spasms in smooth muscle and vascular walls, in addition to providing an anti-inflammatory effect by inhibiting leukotriene synthesis. Prostaglandins are important mediators in the inflammatory process and isopetasin’s positive impact on prostaglandin metabolism contributes to the effectiveness of Petasites extracts. Extracts of the plant also contain volatile oils, flavonoids, tannins, and pyrrolizidine alkaloids. As these alkaloids are believed to be toxic to the liver and carcinogenic in animals, extracts are available in which the pyrrolizidine alkaloids have been removed.²

Mechanisms of Action: The active constituents of Petasites have an antispasmodic effect on vascular walls and appear to have an affinity for cerebral blood vessels. Petasites’ ability to reduce smooth muscle spasm suggests it may be a useful therapeutic tool in treating urinary disorders, menstrual cramps, migraine headaches, kidney stone disorders, obstruction of bile flow, as well as other liver or gastrointestinal disorders associated with smooth muscle spasm.¹ The anti-inflammatory properties of butterbur extracts are attributed to inhibition of lipoxygenase activity and down-regulation of leukotriene synthesis, and are primarily due to the petasin content.

Clinical Indications
Migraine Headache: Two clinical studies using 50 mg of a standardized Petasites extract twice daily for 12 weeks demonstrated its effectiveness as a prophylactic treatment for migraines. Both studies were double blind, placebo controlled, and involved a total of 128 patients. The results of the two studies showed a significant reduction (as much as 60%) in frequency of migraine attacks compared to baseline. Other improvements in the Petasites group included a reduction in the number of days with migraines per month, a decrease in migraine associated symptoms, and diminished duration and intensity of pain. No adverse reactions were reported in either study. Butterbur extract’s high degree of efficacy and excellent tolerability accentuates its value in the prophylactic treatment of migraines.^3,4

Safety: Until recently, side effects from Petasites extracts had not been

reported. In September 2000, a study conducted in Taiwan noted the petasin constituent, responsible for many of butterbur’s pharmacological properties, inhibited the production of testosterone in rat testicular cells, but did not speculate whether this effect would be applicable in humans.⁴ The plant’s pyrrolizidine alkaloids are thought to cause liver damage and to be carcinogenic in animals; however, extracts are commercially available in which the pyrrolizidine alkaloids have been removed. There are no known interactions with either pharmaceutical or over-the-counter anti-inflammatory agents; however, use of Petasites extracts during pregnancy and lactation is contraindicated.¹

Dosage: Typically, Petasites extracts are standardized to contain a minimum of 7.5 mg of petasin and isopetasin. The adult dosage ranges from 50-mg two or three times daily with meals. When used to treat migraines, administration is prophylactic and dosage should be carried out daily for four to six months and then tapered until migraine incidence begins to increase.

I. Eaton J. Butterbur, herbal help for migraine. Nat Pharm 1998;

2:1,23-24.

2. Mauskop, A. Petasites hybridus: ancient medicinal plant is

effective prophylactic treatment for migraine. Townsend Lett

2000;202:104-106.

3. Mauskop A, Grossmann WM, Schmidramsl H. Petasites hybridus

(butterbur root) extract is effective in the prophylaxis of

4. Grossmann WM, Schmidramsl H. An extract of Petasites hybridus is effective in the prophylaxis of migraine. Int J Clin Pharmacol Ther 2000;38:430-435.

5. Lin H, Chien CH, Lin YL, et al. Inhibition of testosterone secretion by S-petasin in rat testicular interstitial cells. Chin J Physiol 2000:43:99-103 migraines. Results of a randomized, double-blind trial. 2000;40:4.

                                  
Hayfever
Summary
A staggering 15 million people suffer with hay fever in the UK and up to 36% of 12 to 14 year olds are affected.