Masseter muscle hypertrophy has been treated for cosmetic purposes using several modalities, including injection of type A or type B botulinum toxin into the masseter muscle. In this report, we compared the efficacy and safety of abobotulinum toxin A with onabotulinum toxin A treatment for masseteric hypertrophy in 25 Korean patients with a conversion factor of 2.5:1 through a controlled, split-face, and evaluator-blinded study. The mean grade of clinical improvement based on clinical assessment was 2.8 ± 0.9 for abobotulinum toxin A and 2.7 ± 0.8 for onabotulinum toxin A at 8 weeks after the injection. At 12 weeks after the injection, the mean grade of clinical improvement based on clinical assessment was 2.9 ± 0.9 for abobotulinum toxin A and 2.7 ± 0.8 for onabotulinum toxin A. More pronounced improvement was observed with abobotulinum toxin A than onabotulinum toxin A in three (12%) patients at 8 weeks and five (20%) patients at 12 weeks. We believe that our data can be used as an essential reference for determining the dose of type A botulinum toxin in the treatment of masseteric hypertrophy.

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