# Butterbur (Petasites hybridus)

**Petasites*; pestilence wort, German *Pestwurz**

**Known today as.** *Petasites hybridus*, of the daisy family, with huge rhubarb-like leaves in damp places.

Kind: Plant  
Poisoning: Pyrrolizidine alkaloids (veno-occlusive disease) (https://thethinkingpress.org/materia-medica/poisons/pyrrolizidine)  
Toxic: yes

> **Caution.** The unprocessed plant is toxic to the liver.

## What was it used for?

Against the plague and pestilential fevers, the root in powder or wine; for the stone, the cough, and worms.

## What does modern science say?

A purified extract prevented migraines in controlled trials, but the raw plant contains pyrrolizidine alkaloids that injure the liver, and concern about liver harm has since made neurologists cautious of it.

## Pharmacognosy and toxicology

- **petasin**: the active sesquiterpene
- **senecionine**: a pyrrolizidine alkaloid

**Mechanism.** Petasins block calcium channels and leukotriene synthesis; the alkaloids injure the liver.

**Dose.** Cumulative from the raw plant; the purified extract is alkaloid-free.

**Standing.** A purified extract prevented migraine in trials; withdrawn in Britain in 2012 over liver cases, and advised against by the American Academy of Neurology since 2015.

## What lore surrounds it?

Its great leaves were used to wrap butter in the heat of summer, hence its English name.

## What did the older authorities say?

**Gerard.** Calls it a sovereign medicine against the plague and pestilent fevers.

## Sources

- Gerard, J. (1597). *The Herball*.
- Grieve, M. (1931). *A Modern Herbal*, “Butterbur.”
- Lipton, R. B., et al. (2004). “Petasites hybridus root (butterbur) is an effective preventive treatment for migraine.” *Neurology* 63.

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*Butterbur.* In *Materia Medica*, edited by B. C. P. Statema. Version 1, revised 2026-09-30. The Thinking Press. https://thethinkingpress.org/materia-medica/butterbur

Historical description, not medical advice.