title: Botulinum Toxin Dosing Trends in Spasmodic Dysphonia Over a 20-year Period.
abstract: OBJECTIVE
  The study aims to (1) identify the botulinum toxin (BTX) dosing trend in a cohort of patients who received at least 20 injections for the treatment of adductor spasmodic dysphonia (ADSD), (2) describe two distinct BTX dosing trends in treating ADSD (a "classic" dosing trend that initially decreases before stabilizing, and a "fluctuating" dosing trend), and (3) determine if patients with the "classic" dosing trend differed in age or in dosing intervals from those with the "fluctuating" dosing trend.
  
  
  METHODS
  This is a retrospective case series.
  
  
  METHODS
  Of 149 patients who received a total of 2484 BTX injections for the treatment of spasmodic dysphonia in 1993-2013, 49 patients received at least 20 injections. The BTX dose and the interval between doses were recorded. The mean dose of injections 1-20 was determined. The age at initial injection, initial dose, and interval in days between treatments were compared for the "fluctuating" and "classic" groups.
  
  
  RESULTS
  The cohort exhibits a significant decrease in dose during the first 10-15 injections. The "fluctuating" group had a significantly shorter interval between injections (mean interval = 97.09 days, SD = 29.41; mean interval = 136.90 days, SD = 43.76, P = 0.002). The mean age at initial dose was not significantly different between the "classic" and "fluctuating" groups.
  
  
  CONCLUSIONS
  The average BTX dose of patients with ADSD who receive long-term injections significantly decreases during the initial 10-15 injections before stabilizing. Patients who exhibit the "fluctuating" dosing pattern have a significantly shorter interval between injections than those with the "classic" dosing pattern.
authors.affiliation: Department of Surgery, UT Southwestern Medical Center, Dallas, Texas.
authors.forename: Arya W
authors.initials: AW
authors.lastname: Namin
authors.affiliation: Saint Louis University Cancer Center, Saint Louis, Missouri.
authors.forename: Kara M
authors.initials: KM
authors.lastname: Christopher
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, Saint Louis University School of Medicine, Saint Louis, Missouri.. Electronic address: eisenbjf@slu.edu.
authors.forename: John F
authors.initials: JF
authors.lastname: Eisenbeis
mesh_terms: D065087:Acetylcholine Release Inhibitors / Q000008:administration & dosage* / Q000009:adverse effects; D000328:Adult; D000368:Aged; D019274:Botulinum Toxins, Type A / Q000008:administration & dosage* / Q000009:adverse effects; D004334:Drug Administration Schedule; D055154:Dysphonia / Q000175:diagnosis / Q000188:drug therapy* / Q000503:physiopathology; D005260:Female; D006801:Humans; D007267:Injections; D007821:Laryngeal Muscles / Q000187:drug effects* / Q000294:innervation; D008297:Male; D008875:Middle Aged; D008923:Missouri; D010818:Practice Patterns, Physicians' / Q000639:trends*; D012189:Retrospective Studies; D013997:Time Factors; D016896:Treatment Outcome; D014831:Voice / Q000187:drug effects*
chemical_list: D065087:Acetylcholine Release Inhibitors; D019274:Botulinum Toxins, Type A
keywords: Botulinum toxin; Dosing intervals; Initial dose; Spasmodic dysphonia; Trend