What is the evidence supporting Botox for migraine?

The FDA approved Botox for chronic migraine based on the results of two studies, PREEMPT 1 and PREEMPT 2. These studies, published in the March 2010 issue of Cephalalgia, and involving 1,384 adults in North America and Europe, demonstrated that patients treated with Botox experienced a major decrease in the frequency of headache days.

Specifically, the studies showed that Botox (OnabotulinumtoxinA) was statistically significantly superior to placebo for the primary endpoint, frequency of headache days per 28 days relative to baseline. In those patients receiving Botox, there was a significant reduction from baseline in both headache and migraine days, cumulative hours of headache on headache days and frequency of moderate/severe headache days. It was safe and well tolerated, with few treatment-related adverse events. Few patients (3.5% Botox/1.4% placebo) discontinued due to adverse events. Botox was also significantly favored in all secondary endpoint comparisons. Based on the strength of this evidence, the FDA approved Botox for the treatment of Chronic Migraine Headaches in adults.