OnabotulinumtoxinA improves masseter muscle prominence

OnabotulinumtoxinA treatment showed a marked reduction in masseter muscle prominence with both 48- and 72-unit doses, according to a study presented at the American Society for Dermatologic Surgery virtual meeting.

“The rational for evaluating onabotulinumtoxinA 47 units and 72 units in adults with masseter muscle prominence is that we recognize the masseter muscle participates in the widening of the lower face which is an aesthetic concern as it can make a feminine face appear more masculine,” Sabrina Fabi, MD, volunteer assistant clinical professor at Cosmetic Laser Dermatology in San Diego, said.

A 6-month, double-blind, randomized phase 2 study evaluated the effect of either 48 or 72 units of onabotulinumtoxinA in patients with masseter muscle prominence (MMP), as compared with placebo.

Of 150 patients enrolled in the study, 53 received the 48-unit dose, 46 received the 72-unit dose and 46 received a placebo injection of saline.

At day 90, 90.6% of those in the 48-unit dose group had a response of at least a 3-grade improvement in investigator-assessed Masseter Muscle Prominence Scale, while 91.3% of those in the 72-unit group experienced the same result. The placebo group had a 21.7% response rate.

An improvement of at least 2 grades in Patient Self-Assessment of Change was reported in 90.6% of those in the 48-unit group and 73.9% of those in the 72-unit group, compared with 21.7% of the placebo group.

Treatment-emergent serious adverse events occurred in one patient in the placebo group and one patient in the 48-unit group.

“Masseter muscle prominence was significantly reduced after a single treatment, whether it was 48 units or 72 units, in both the masseter muscle prominence scale used by investigators or by the participant,” Fabi said. “Most onabotulinumtoxinA-treated participants reported being less bothered by their prominence after treatment, improving their overall psychosocial well-being and having greater satisfaction with their outcomes.”