The most studied dose of butterbur for migraine prevention is 75 mg taken twice daily, for a total of 150 mg per day. At this dose, clinical trials found a 48% reduction in monthly migraine attacks over four months. A lower dose of 50 mg twice daily was also tested but showed weaker results, reducing attacks by only 36%, which was not statistically significant compared to placebo.
What the Clinical Evidence Shows
The key trial behind these numbers enrolled 245 people with regular migraines and randomly assigned them to one of three groups: 75 mg twice daily, 50 mg twice daily, or placebo. After four months, the higher-dose group had nearly half as many migraine days, while the placebo group saw a 26% reduction (a reminder that placebo effects in migraine trials are consistently strong). The difference between 75 mg twice daily and placebo was statistically significant. The 50 mg dose was not, making 75 mg twice daily the only dose with solid evidence behind it.
Butterbur is used for prevention, not as an acute treatment when a migraine is already underway. Like most preventive approaches, it requires consistent daily use over weeks before the effect becomes noticeable. The major trial measured outcomes at the four-month mark, so patience is part of the equation.
How Butterbur Works Against Migraines
The butterbur plant contains two active compounds, petasin and isopetasin, that work through a mechanism relevant to migraine biology. They interact with pain-sensing nerve fibers by initially activating, then desensitizing, specific ion channels on those nerves. Think of it like ringing a doorbell until the person inside stops answering. Once desensitized, these nerve fibers release less of a signaling molecule called CGRP, which plays a central role in triggering migraine pain and the inflammation that accompanies it.
This is notable because CGRP is the same target that newer prescription migraine drugs are designed to block. Butterbur appears to reach a similar endpoint through a different route: rather than blocking CGRP directly, it quiets the nerve endings that release it. The extract also reduces the production of inflammatory compounds through other pathways, giving it a multi-pronged anti-inflammatory effect.
The Safety Problem You Need to Know About
Butterbur’s story is complicated by a serious safety concern. The raw plant contains pyrrolizidine alkaloids (PAs), toxic compounds that can damage the liver, harm the lungs, and potentially cause cancer with long-term exposure. Any butterbur product must be processed to remove these alkaloids and labeled or certified as PA-free. Products containing PAs should never be used, especially during pregnancy, where they can cause birth defects and liver damage.
Even with PA-free products, the picture isn’t entirely reassuring. The National Institutes of Health notes that rare cases of liver injury have been reported with products that were labeled PA-free. Whether those cases reflect contamination, individual sensitivity, or some other compound in the plant remains unclear. This safety signal was significant enough that in 2015, the American Academy of Neurology retired its 2012 guideline that had recommended butterbur for migraine prevention. The organization stated that the recommendations in the retired guideline are no longer considered valid or supported.
That doesn’t mean butterbur is banned or proven dangerous at standard doses. It means the medical establishment decided the risk-benefit balance was uncertain enough to pull back its endorsement. For someone considering butterbur, this context matters.
Choosing a Product
If you decide to try butterbur, product quality is the single most important factor. Look for extracts explicitly labeled PA-free. The formulation used in the major clinical trials was a standardized extract called Petadolex, which set the benchmark for PA removal. Not all butterbur supplements on the market meet the same manufacturing standards, and because dietary supplements aren’t regulated as strictly as prescription drugs, labeling claims don’t always reflect what’s actually in the bottle.
Third-party testing seals from organizations that independently verify supplement contents add a layer of confidence, though no certification system specifically tests for PA levels in butterbur. Choosing a product from a manufacturer that provides a certificate of analysis showing PA content below detection limits is the closest thing to a guarantee available.
Practical Considerations
The standard approach in the clinical trials was straightforward: one 75 mg capsule in the morning and one in the evening, taken consistently for at least three to four months before judging whether it’s working. Mild gastrointestinal side effects, particularly burping, were the most commonly reported issue in trials.
Butterbur is a preventive strategy, meaning it’s aimed at reducing how often migraines occur over time rather than stopping one that’s already started. It can be used alongside acute treatments you take during an attack. Given the AAN’s withdrawal of its recommendation and the lingering liver safety questions, many neurologists now favor other preventive options first, including magnesium, riboflavin, and prescription medications, while acknowledging that butterbur has some of the stronger clinical trial data among herbal supplements for migraine.