The efficacy of two formulations of botulinum toxin type A for masseter reduction: a split-face comparison study.

[BACKGROUND] Botulinum toxin type A (BTA) is now extensively used to address cosmetic concerns. OnabotulinumtoxinA (ONA, Botox; Allergan Inc., Irvine, CA) received FDA approval for upper face rejuvenation, including glabella frown lines and crow's-feet lines. The other off-label uses for lower face conditions have been utilized for contouring purposes, especially masseter hypertrophy. Recently, a new Daewoong BTA, (NABOTA, NBT, Daewoong Pharmaceutical, Seoul, Korea), was recently introduced.

[OBJECTIVE] To compare efficacy and safety of ONA and NBT for masseter reduction.

[METHODS] Thirty-five subjects with masseter hypertrophy were randomly injected with 25 units of ONA on one side and 25 units of NBT on the other side into masseter. Standardized photographic documentation was obtained at baseline, 1, 3 and 6 months after treatment. The mean volume of masseter was acquired by using three-dimensional computed tomography (3-D CT) at baseline, 3-, and 6-month follow-up visits. In addition, patients' satisfaction and side effects were also record at every follow-up visits.

[RESULTS] The mean masseter volume on the sides treated with ONA and NBT at baseline were 21.20 ± 4.23 cm and 21.26 ± 4.58 cm, respectively. There was no statistically significant difference in the mean volume of both sides (p= 0.827). The mean masseter volume at 3- and 6-month follow-up visits reduced significantly on both ONA and NBT sides (p< 0.001 and p< 0.001, respectively). However, there was no statistically significant difference in mean masseter volume when comparing between ONA and NBT sides at 3 and 6 months after treatment (p= 0.769 and p = 0.346, respectively). There was also no statistically significant difference in masseter reduction when compared between ONA and NBT sides evaluated by physicians and patients at each follow-up visit. No side effect on both sides was reported after injection.

[CONCLUSIONS] This study demonstrated that ONA and NBT provided comparable efficacy and safety for masseter reduction.