title: Dilution volume of botulinum toxin type A for the treatment of glabellar rhytides: does it matter?
abstract: BACKGROUND
  Because well-controlled studies examining the efficacy and safety of various dilutions of botulinum toxin type A (BTX-A) have not been performed, dilutions used in clinical practice are chosen at the discretion of the clinician.
  
  
  OBJECTIVE
  The objectives were to determine the most effective BTX-A dilution for the glabellar region, the relationship between dilution and duration of effect, and the side effect profile of each dilution in women with glabellar rhytides.
  
  
  METHODS
  Eighty women with moderate-to-severe wrinkles at maximum frown were randomized to one of four dilution groups in a 48-week, single-center, double-blind, parallel-group study. Subjects received 30 U BTX-A (BOTOX, Allergan, Inc.) injected into the glabellar region at dilutions of 100, 33.3, 20, or 10 U/mL. Outcome measures included trained-observer and subject assessment of wrinkle severity at repose and at maximum muscle contraction using the Facial Wrinkle Scale (FWS) and adverse events.
  
  
  RESULTS
  All dilutions of BTX-A effectively improved glabellar rhytides as assessed by both trained observers and subjects using the FWS. No significant differences on FWS scores were seen among the dilution groups by trained observers at any time point. Although a difference among groups was seen in subject-assessed responder rates, there was no obvious relationship between dilution and response. BTX-A treatment was well tolerated, and there were no significant differences between the four dilution groups in the number of subjects reporting adverse effects.
  
  
  CONCLUSIONS
  In this study, the dilution of BTX-A was not critical to the success of treatment.
authors.affiliation: Division of Dermatology, University of British Columbia, Vancouver, British Columbia, Canada. alastair@carruthers.net
authors.forename: Alastair
authors.initials: A
authors.lastname: Carruthers
authors.forename: Jean
authors.initials: J
authors.lastname: Carruthers
authors.forename: Joel
authors.initials: J
authors.lastname: Cohen
mesh_terms: D000328:Adult; D019274:Botulinum Toxins, Type A / Q000008:administration & dosage*; D004311:Double-Blind Method; D005145:Face; D005260:Female; D006801:Humans; D007267:Injections; D008875:Middle Aged; D009465:Neuromuscular Agents / Q000008:administration & dosage*; D015595:Skin Aging / Q000187:drug effects*; D016896:Treatment Outcome
chemical_list: D009465:Neuromuscular Agents; D019274:Botulinum Toxins, Type A