The special butterbur plant extract was extremely well tolerated in all three clinical trials. Compared to placebo only burping was significantly more often reported by patients.
According to a recent publication the overall frequency of suspected adverse reactions outside of clinical trials was as low as 0.02%. One reversible case of a hepatitis was evaluated by an independent expert in the field of hepatology to be “probably” caused by Petadolex. Over the counter nonsteroidal anti-inflammatory drugs (NSAIDs) that are widely used have a two- to 8 fold higher incidence of hepatitis.
Several toxicity studies were conducted in Wistar rats according to international guidelines. A NOAEL (no adverse effect level) could be established being well above and at an adequate safety distance of the recommended dose in humans.
Butterbur plant extract is included in the treatment guidelines of the German Society of Neurology and will also be include in the upcoming new version of the guideline of the German Migraine and Headache Society as a second choice treatment following beta-blockers.