title: High versus low concentration botulinum toxin A for benign essential blepharospasm: does dilution make a difference?
abstract: OBJECTIVE
  To evaluate the efficacy and side effects of concentrated versus dilute botulinum toxin A in treating benign essential blepharospasm.
  
  
  METHODS
  The authors performed a prospective randomized clinical trial of 16 patients with an established diagnosis of benign essential blepharospasm. Patients were randomized to receive low concentration (control, 10 U/ml) injections on one side and high concentration (experimental, 100 U/ml) injections on the other. They were surveyed on a scale of 1 to 10 regarding pain, bruising, and redness immediately after the injection. During their return visit, at an established interval of 1 to 3 months, patients were questioned regarding complications (ptosis, diplopia, tearing, and dry eye), duration of relief, and side preferred. Patients were followed over 8 months for 1 to 6 repeat injections, with the side given the higher concentration alternated at each visit.
  
  
  RESULTS
  With 16 patients, there were a total of 42 visits and 84 observations (eyes) documented. Using the Wilcoxon rank sum test, there was a statistically significant reduction in pain scores (1.94 vs. 4.59, p < 0.001) on the experimental side versus the control side. Patient assessment revealed no significant difference in bruising, redness, complications of injection, side preference, or length of relief of symptoms.
  
  
  CONCLUSIONS
  Compared with the control, the high concentration botulinum toxin A demonstrated a 58% reduction in perceived pain. Patients did not report a significant difference in efficacy or complications with either dilution.
authors.affiliation: Alabama Ophthalmology Associates, P.C., Division of Ophthalmic Plastic and Reconstructive Surgery, Birmingham, Alabama, USA. aoa_boyle@bellsouth.net
authors.forename: Michael H
authors.initials: MH
authors.lastname: Boyle
authors.forename: Gerald
authors.initials: G
authors.lastname: McGwin
authors.forename: Courtney E
authors.initials: CE
authors.lastname: Flanagan
authors.forename: Matthew G
authors.initials: MG
authors.lastname: Vicinanzo
authors.forename: John A
authors.initials: JA
authors.lastname: Long
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001764:Blepharospasm / Q000188:drug therapy*; D019274:Botulinum Toxins, Type A / Q000008:administration & dosage* / Q000009:adverse effects; D003288:Contusions / Q000139:chemically induced; D004305:Dose-Response Relationship, Drug; D004890:Erythema / Q000139:chemically induced; D005260:Female; D006801:Humans; D007267:Injections; D008297:Male; D008875:Middle Aged; D009465:Neuromuscular Agents / Q000008:administration & dosage* / Q000009:adverse effects; D009994:Osmolar Concentration; D010146:Pain / Q000139:chemically induced / Q000503:physiopathology; D012720:Severity of Illness Index; D016896:Treatment Outcome
chemical_list: D009465:Neuromuscular Agents; D019274:Botulinum Toxins, Type A