Botulinum toxin, a potent muscle relaxant, has been found to have
analgesic effects in patients with various
pain syndromes. Both in vitro and in vivo studies showed the ability of the toxin to block the release of
pain neurotransmitters, such as
substance P,
glutamate, and
calcitonin gene-related peptide. The effect of the toxin, and specifically of one of its serotypes,
botulinum neurotoxin type A, on
headaches, has been extensively studied. This serotype is available in the United States in 3 forms, including as
onabotulinumtoxinA. Data from clinical trials confirmed the efficacy, safety, and tolerability of
onabotulinumtoxinA in the prophylactic treatment of chronic
migraine, the most severe and debilitating type of
migraine, in adults. The
drug was approved by the Food and Drug Administration for this indication in 2010. The
drug was not found to be effective for episodic
migraine or
tension-type headache. Noncontrolled studies suggest the efficacy of the toxin for
headache associated with craniocervical
dystonia. Proper injection technique and appropriate patient selection are essential for achieving positive results
after treatment with
onabotulinumtoxinA. The recommended injection paradigm combines a fixed site/fixed dose and follow the
pain approaches, with the toxin injected to multiple sites of the head and neck, at a total dose of 155U-195U. The treatment is given at intervals of 12 weeks on average. The efficacy of
onabotulinumtoxinA for some
headaches, its long duration of action, and its favorable adverse effect profile make it a viable treatment option for the appropriate
headache patients. The
drug may be particularly suitable for patients who cannot tolerate, or are not compliant with, the daily intake of oral
headache preventive drugs.