About Butterbur
Petasites hybridus root. Pyrrolizidine-alkaloid-free (PA-free) CO2 extracts (e.g., Petadolex) reduced migraine frequency in RCTs, and Ze 339 has allergic-rhinitis data. CRITICAL SAFETY: only PA-free extracts are acceptable — raw/unprocessed butterbur is hepatotoxic. Some authorities withdrew endorsement over liver-toxicity signals; EU/UK restrict it.
What Butterbur supports
- May reduce migraine frequency — supported by RCTs, but only pyrrolizidine-alkaloid-free extracts are safe.
How much Butterbur to take
The RDA prevents deficiency. The effective range is what clinical trials used to actually move the outcome.
Effective
50–75
mg
PA-free extract 50-75 mg twice daily in migraine-prophylaxis RCTs.
Clinical evidence
Moderate clinical evidence. Positive migraine-prophylaxis RCTs; hepatotoxicity concern led some bodies to withdraw endorsement.
NIH Fact Sheet