OnabotulinumtoxinA in the treatment of patients with chronic migraine: clinical evidence and experience.

Chronic migraine is a debilitating neurobiological disorder that affects approximately 1.4-2.2% of the population worldwide. Patients with chronic migraine have 15 or more headache days per month, with at least 8 days per month that meet the criteria for migraine. Injection of onabotulinumtoxinA, using a standardized injection protocol, was approved by the US Food and Drug Administration in 2010 for the treatment of chronic migraine. The approval was made based on results from two large, randomized, double-blind placebo-controlled trials: the Phase III Research Evaluating Migraine Prophylaxis Therapy (PREEMPT) trials. Since then, numerous studies have been performed investigating the short-term and long-term benefits, risks and complications of the use of onabotulinumtoxinA injections for the treatment of chronic migraine. The purpose of this narrative review is to describe the currently available clinical evidence for the use of onabotulinumtoxinA injections for treating patients with chronic migraine.