OnabotulinumtoxinA: Discussion of the evidence for effectiveness of OnabotulinumA and its place in chronic migraine treatment.

OnabotulinumtoxinA is a potent inhibitor of muscle contraction that acts by preventing the release of acetylcholine at the neuromuscular junction. In pain states such as migraine, its mechanism of action is not yet fully elucidated and probably relates to the phenomena of central and peripheral sensitization within the trigeminal system. Migraine is a prevalent and disabling disorder and, especially in its variant of chronic migraine (CM), is associated with relevant symptomatic and socioeconomic burden, the objective of preventive treatment being to reduce the frequency, duration, or severity of migraine attacks. OnabotulinumtoxinA, administered by intramuscular injection, is approved for the prevention of CM and is among the most utilized preventive treatments in CM and fundamental to clinical practice. The efficacy and safety of OnabotulinumtoxinA in the treatment of CM have been verified by the PREEMPT 1 and 2 studies and confirmed by the real-world studies that followed, including the COMPEL, REPOSE, and CM PASS. OnabotulinumtoxinA not only reduces headache days but also leads to improvement in functioning and quality of life, thereby reducing migraine impact. Data about its pathophysiology, efficacy, and its place in CM treatment in the era of CGRP monoclonal antibodies are reviewed and discussed here.