Adverse events associated with botulinum toxin injection: a multidepartment, retrospective study of 5310 treatments administered to 1819 patients.

Background: The injection of botulinum toxin is now commonly used for many therapeutic and cosmetic purposes but because of its increased use more adverse events are being reported.

Objective: To retrospectively evaluate and analyze the safety of botulinum toxin injections in terms of purpose and the type of toxin administered.

Materials And Methods: Data were collected on 1819 patients who underwent a total of 5310 treatments between 2005 and 2011 at a single tertiary medical center. Information on the dosage, treatment purpose, type of botulinum toxin, and any adverse events associated with these treatments were collected and analyzed. The generalized estimating equation (GEE) with the logistic link function was used to estimate the overall frequencies of adverse events. A multivariable GEE with the logistic link function was used to identify the factors associated with adverse events.

Results: Among the 5310 botulinum toxin treatments in our study cohort, 2258 of which (42.5%) were used to treat hemifacial spasm, 184 adverse events (3.73%) were recorded, 114 (2.26%) muscle-related, and 71 (1.47%) muscle-unrelated. The highest number of adverse events (8.29%) was associated with the treatment of blepharospasm and the lowest (1.07%) with masseter hyperplasia. By multivariate analysis, the odds ratio for females was 1.577 (95% confidence interval [CI] = 1.052-2.364; p = 0.027) and for the dose was 1.006 (95% CI = 1.002-1.010; p = 0.005). When compared with upper face wrinkles, the odds ratio was 2.510 (95% CI = 1.400-4.499; p = 0.002) for blepharospasm, 0.375 (95% CI = 0.202-0.695; p = 0.002) for cervical dystonia, and 0.114 (95% CI: 0.015-0.862; p = 0.035) for masseter hyperplasia.

Conclusion: When injecting botulinum toxin for cosmetic purposes, practitioners should be cautious, especially when targeting the areas around the eyes, as these treatments are prone to cause adverse events.