Double-blind, randomized, placebo-controlled, dose-response study of the safety and efficacy of botulinum toxin type a in subjects with crow's feet

BACKGROUND. Published evidence suggests that botulinum toxin type A (BTX-A) is an effective treatment for crow's feet. However, few dose-ranging studies have been performed. OBJECTIVES. To assess the safety and efficacy of a single treatment with one of four doses of BTX-A (Botox/Vistabel, Allergan Inc) compared with placebo for the improvement of crow's feet. METHODS. Subjects received a single bilateral treatment of 18, 12, 6, or 3 U of BTX-A or placebo injected into the lateral aspect of the orbicularis oculi muscle (parallel-group, double-blind design). Investigators and subjects rated crow's feet severity at maximum smile on day 7 and at 30-day intervals from days 30 to 180. RESULTS. As observed by both investigators and subjects, all doses of BTX-A resulted in improvements in crow's feet severity when compared with placebo. A dose-dependent treatment effect for efficacy was observed, with higher doses having an increased magnitude and duration of effect. However, a clear differentiation between the 18 U and 12 U doses was not apparent. Few adverse events were reported, with no statistically significant differences between BTX-A and placebo in the incidence of subjects experiencing adverse events. CONCLUSION. BTX-A is safe and effective in decreasing the severity of crow's feet, with 12 U per side suggested as the most appropriate dose.