Botulinum toxin in men: review of relevant anatomy and clinical trial data.

BACKGROUND Botulinum toxin is widely used for facial aesthetics, and its use in men continues to increase. OBJECTIVE To provide a review of pertinent male anatomic features and updated clinical information on the use of botulinum toxin in men. METHODS A Medline search was performed for publications on sex differences in facial anatomy and on clinical studies examining the role of sex in botulinum toxin treatment. RESULTS There are substantial facial anatomic differences between the sexes, with men having increased cranial size, unique cranial shape, greater skeletal muscle mass, higher density of facial blood vessels, and more-severe facial rhytides. A review of sex and botulinum toxin treatment identified 17 clinical studies with 5,646 total participants, of whom 629 (11.1%) were male. Only two studies accounted for sex in study design or subgroup analysis. Both studies found abobotulinumtoxinA to be less effective in men. An additional study examining onabotulinumtoxinA dosing in men found that higher doses than typically used in women were more efficacious. There were not more adverse events in male participants in any study. CONCLUSION Despite sex differences in facial anatomy, the use of botulinum toxin in men is inadequately studied with regard to dosing, efficacy, and safety.