A Multicenter Phase II Study Evaluating the Safety and Efficacy of Botulax in Asian Patients with Benign Masseteric Hypertrophy

Background: Benign masseteric hypertrophy (BMH) is a condition in which the thickness of the masseter muscle is increased, resulting in jawline prominence with undesirable aesthetic appearance. Botulinum toxin type A (BTA) injection is a promising treatment option, but its effective dose remains debated. Methods: Adults over 19 diagnosed with BMH through visual examination and palpation related to a masseter muscle prominence were selected; 80 patients were randomly assigned into five groups (placebo group and 4 groups with different doses of BTA – 24U, 48U, 72U, 96U on both sides of the jaw) and treated with placebo or BTA once at their baseline visit. During each follow-up, the treatment efficacy was evaluated via ultrasound examination of the masseter muscle, 3D facial contour analysis, visual evaluation by the investigator, and patient satisfaction evaluation. Results: The mean age of the 80 patients was 42.7±9.98 years; 68.75% were women. The mean change of the MMT during the maximum clenching state after 12 weeks of drug administration compared to the baseline in the 24U, 48U, 72U, and 96U groups were -2.33±0.41 mm, -3.35±0.42 mm, -2.86±0.42 mm, and -3.79±0.42 mm. All treatment groups showed a statistically significant decrease compared to placebo. Regarding subjective satisfaction, all treatment groups, except the 24U group at 4 weeks, showed higher satisfaction than the placebo group during all visits. No significant adverse events were noted. Conclusions: BTA administration of at least 48U for BMH is more cost-effective than high-dose units and has a low possibility of side effects.