OnabotulinumtoxinA for treatment of chronic migraine: pooled analyses of the 56-week PREEMPT clinical program.

Objective: To evaluate safety and efficacy of onabotulinumtoxinA (BOTOX(®) ) as headache prophylaxis in adults with chronic migraine.

Background: Chronic migraine is a prevalent, disabling, and undertreated neurological disorder. OnabotulinumtoxinA is the only approved prophylactic therapy in this highly disabled patient population.