title: Bilateral, double-blind, randomized comparison of 3 doses of botulinum toxin type A and placebo in patients with crow's feet.
abstract: BACKGROUND
  Optimum dosing for botulinum toxin type A (BTX-A) in crow's feet remains to be defined.
  
  
  OBJECTIVE
  Our purpose was to compare the efficacy and safety of 3 doses of BTX-A and placebo in patients with crow's feet.
  
  
  METHODS
  Patients were treated with 6, 12, or 18 units of BTX-A in orbicularis oculi muscle on one side and placebo contralaterally (double-blind design). At 16 weeks after injection, patients were treated with 12 or 18 units of BTX-A bilaterally (open-label design). Trained observers and patients rated the wrinkles on a scale of 0 (none) to 3 (severe) at maximum contraction and repose and at baseline and 4-week intervals over a 16-week period after injection.
  
  
  RESULTS
  All doses of BTX-A were significantly superior to placebo with no clear dose-response relationship. Benefits of the second injection lasted longer than the first. Few and mild adverse events were seen.
  
  
  CONCLUSIONS
  BTX-A is a safe and effective treatment for crow's feet. Benefits are more sustained with repeat treatment.
authors.affiliation: Clinical Research Specialists, Santa Monica, CA 90404, USA. cranleyuk@aol.com
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Lowe
authors.forename: Gary
authors.initials: G
authors.lastname: Lask
authors.forename: Paul
authors.initials: P
authors.lastname: Yamauchi
authors.forename: Donna
authors.initials: D
authors.lastname: Moore
mesh_terms: D000368:Aged; D019274:Botulinum Toxins, Type A / Q000008:administration & dosage*; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D004334:Drug Administration Schedule; D004954:Esthetics; D005152:Facial Muscles / Q000187:drug effects*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007279:Injections, Subcutaneous; D008297:Male; D008875:Middle Aged; D009465:Neuromuscular Agents / Q000008:administration & dosage*; D011336:Probability; D011446:Prospective Studies; D012016:Reference Values; D015595:Skin Aging / Q000187:drug effects*; D016896:Treatment Outcome
chemical_list: D009465:Neuromuscular Agents; D019274:Botulinum Toxins, Type A