In 2012 AAN published in Neurology guidelines entitled: "Evidence-based guideline update: NSAIDs and other complementary treatments for episodic migraine prevention in adults: report of the Quality Standards Subcommittee of the American Academy of Neurology and the American Headache Society". (https://n.neurology.org/content/80/9/868). In this paper it was written "Petasites (butterbur) is effective for migraine prevention and should be offered to patients with migraine to reduce the frequency and severity of migraine attacks (Level A)"
In 2013 Dr. Mauskop's concerns regarding the safety of Petasites (butterbur) extract and response from the authors (https://n.neurology.org/content/80/9/868) that no detectable toxic pyrrolizidine alkaloids was found in the Petadolex samples.
The recomendations from 2012 was retired and was not updated so far. What do You think ?