OnabotulinumtoxinA for the treatment of headache: an updated review.

Botulinum toxin (BT) is a neurotoxin produced by Clostridium botulinum, a gram-positive anaerobic bacterium. Systemic human intoxication from BT following oral ingestion results in acute and life-threatening muscle paralysis called botulism. BT has a wide scope of therapeutic uses, including conditions associated with increased muscle tone, smooth muscle hyperactivity, salivation, sweating, and allergies, as well as for cosmetic purposes. Several commercial forms of BT are available for medical use, including Botox (onabotulinumtoxinA). Multiple studies have found evidence of an analgesic effect of onabotulinumtoxinA and demonstrated the benefits of its use for the treatment of various chronic pain disorders. In this review, we provide an update on the use of onabotulinumtoxinA for the treatment of headache disorders.