Botulinum toxin was found to reduce migraine frequency in adults with chronic migraine by 2 days per month without significant adverse events, according to systematic review and meta-analysis results published in BMJ Open.

This review and meta-analysis of randomized controlled trials was conducted to evaluate the efficacy and safety of botulinum toxin in the prevention of migraine. The 28 trials reviewed included 4190 adults with chronic or episodic migraine with or without medication overuse headache. The researchers used Cochrane methods to review the studies and analyzed each one for a period of 12 weeks post-treatment.

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Botulinum toxin was compared with placebo in 23 trials including 3912 participants, 60% of whom had medication overuse headache. On average, treatment was associated with a reduction of 3.1 migraine days per month. After excluding studies with a high risk for bias, the 2 remaining trials (n=1384) had an average reduction of 1.9 migraine days per month with botulinum toxin compared with placebo. No significant differences were noted for the 3 trials in which botulinum toxin was compared with alternative oral prophylactic agents.

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In 4 small trials, improvements in migraine severity (assessed with a 0–10 cm visual analog scale) were assessed. In those trials, patients with chronic and episodic migraine who were treated with botulinum toxin reported improvements in migraine severity of −2.70 cm (95% CI, −3.31 to −2.09; n =75) and of −4.9 cm (95% CI, −6.56 to −3.24; n =34), respectively.

Botulinum toxin was found to have nearly double the risk for treatment-related adverse events compared with placebo, but reduced risk compared with active comparators (relative risk, 0.76; 95% CI, 0.59-0.98). The withdrawal rate with botulinum toxin was low (3%).

Study limitations include a poor rate of reporting on the primary outcome (migraine days).

“The difference between chronic and episodic migraine diagnoses is arbitrary and so there is no pathophysiological reason that treatment with botulinum toxin would be efficacious in people with 15 days of headache per month and inefficacious in people with 14 days of headache per month in a stepwise fashion,” noted the reviewers. “The treatment may well be useful for episodic migraine, particularly in high frequency episodic migraine, but data is lacking.”


Herd CP, Tomlinson CL, Rick C, et al. Cochrane systematic review and meta-analysis of botulinum toxin for the prevention of migraine [published online July 16, 2019]. BMJ Open. doi:10.1136/bmjopen-2018-027953

This article originally appeared on Clinical Pain Advisor