Butterbur extracts have been found to contain hepatotoxic pyrrolizidine alkaloids at the retail level before. These alkaloids have also been shown to cause cancer in animal models before and should be assumed to be carcinogenic for that reason. Germany has gone as far as to regulate these alkaloids, limiting intake to 1μg per day, for no more than 6 weeks per year. Furthermore, because of hepatotoxic concerns, these extracts are not recommended during pregnancy or breastfeeding. The adverse effects of butterbur reported in clinical trials include mainly gastrointestinal problems, such as nausea, flatulence, and belching. In 2015, the American Academy of Neurology withdrew its original endorsement of butterbur due to safety concerns. However, the Canadian Headache Society still recommends its use in migraine prevention for a selected number of patients based on their clinical features and co-existing disorders. Long-term health effects and interaction of butterbur with other drugs have not been well documented. However, it can theoretically interact with certain blood pressure and heart medications, as well as with drugs that can induce a liver enzyme called CYP3A4 (i.e. St. John's wort, carbamazepine, phenytoin, rifampin); this interaction can potentially lead to increased concentration of the toxic alkaloids. Prior cases of liver damage have been reported from patients who were taking butterbur with cases varying in adverse effects from cholestasis and inflammation, to liver failure resulting in transplantation
Petasites hybridus
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Craniopagus parasiticus
Cedecea davisae
Hydnocarpus wightianus
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Cerbera odollam