title: Prospective, double-blind, randomized, parallel-group, dose-ranging study of botulinum toxin type A in men with glabellar rhytids.
abstract: BACKGROUND
  The effective dose for treating glabellar lines with botulinum toxin type A in men has not been studied adequately.
  
  
  OBJECTIVE
  To compare the safety, efficacy, and duration of response of four doses of botulinum toxin type A on glabellar rhytids in men.
  
  
  METHODS
  Eighty men were randomized to receive a total dose of either 20, 40, 60, or 80 U of botulinum toxin type A (BOTOX, BOTOX Cosmetic, or Vistabel, Allergan, Inc., Irvine, CA, USA) in the glabellar area. Glabellar lines were assessed at rest and maximum frown by a trained observer at baseline, 2 and 4 weeks, and monthly thereafter. Patients provided self-evaluations at the same visits. Adverse events were monitored throughout.
  
  
  RESULTS
  The 40, 60, and 80 U doses of botulinum toxin type A were consistently more effective in reducing glabellar lines than the 20 U dose (duration, peak response rate, improvement from baseline). There was a dose-dependent increase in both the response rate at maximum frown and the duration of effect assessed by the trained observer. In addition, the participants reported a dose-dependent reduction in the ability to frown, improvement in their global assessment, and increased feelings of attractiveness, self-confidence, and satisfaction. The incidence of adverse events was not increased with higher doses.
  
  
  CONCLUSIONS
  Male participants with glabellar rhytids benefit from starting doses of at least 40 U of botulinum toxin type A.
authors.affiliation: Department of Dermatology, University of British Columbia, 943 West Broadway, Ste. 820, Vancouver, British Columbia V5Z 4E1, Canada. alastair@carruthers.net
authors.forename: Alastair
authors.initials: A
authors.lastname: Carruthers
authors.forename: Jean
authors.initials: J
authors.lastname: Carruthers
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D019274:Botulinum Toxins, Type A / Q000008:administration & dosage*; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D006801:Humans; D008297:Male; D008875:Middle Aged; D009465:Neuromuscular Agents / Q000008:administration & dosage*; D011446:Prospective Studies; D012008:Recurrence; D015361:Rhytidoplasty; D015595:Skin Aging / Q000187:drug effects*; D016896:Treatment Outcome
chemical_list: D009465:Neuromuscular Agents; D019274:Botulinum Toxins, Type A