title: Double-blind, randomized, placebo-controlled, dose-response study of the safety and efficacy of botulinum toxin type A in subjects with crow's feet.
abstract: 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.
  
  
  OBJECTIVE
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Cranley Clinic, London, United Kingdom. cranleyuk@aol.com
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Lowe
authors.forename: Benjamin
authors.initials: B
authors.lastname: Ascher
authors.forename: Marc
authors.initials: M
authors.lastname: Heckmann
authors.forename: Catherine
authors.initials: C
authors.lastname: Kumar
authors.forename: Stephanie
authors.initials: S
authors.lastname: Fraczek
authors.forename: Nina
authors.initials: N
authors.lastname: Eadie
mesh_terms: D000328:Adult; D019274:Botulinum Toxins, Type A / Q000008:administration & dosage*; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009465:Neuromuscular Agents / Q000008:administration & dosage*; D015361:Rhytidoplasty; D015595:Skin Aging / Q000187:drug effects*
chemical_list: D009465:Neuromuscular Agents; D019274:Botulinum Toxins, Type A