Botulinum toxin A and B: a comparative dosing study for spasmodic dysphonia.
OBJECTIVE
The purpose of this study was to find the conversion factor, safety, and efficacy of type A to type B toxin for laryngeal muscles.


METHODS
Thirty-two patients with adductor spasmodic dysphonia with stable doses of A toxin to manage their symptom were given type B toxin starting at a conversion of 1 U of BTX-A to 50 U of BTX-B. The patients were followed for 1 year, and doses adjusted according to response.


RESULTS
The conversion factor was found to be 52.3 U:1 U. The onset of action of type B was more rapid (2.09 days vs 3.2 days [P = 0.028]), with a shorter duration of benefit (10.8 weeks vs 17 weeks [P = 0.002). The safety profile for A and B toxin appeared the same, with 3 patients receiving Myobloc reporting dry mouth.


CONCLUSIONS
This study shows that a conversion factor of 52.3:1 Myobloc (BTX-B) to Botox (BTX-A) and that Myobloc is an effective alternative to Botox (BTX-A) for patients with spasmodic dysphonia.
Blitzer
Andrew
A
College of Physicians and Surgeons, Columbia University, New York Center for Voice and Swallowing Disorders, New York, NY 10019, USA. AB1136@aol.com
D001905:Botulinum Toxins / Q000008:administration & dosage* / Q000627:therapeutic use; D019274:Botulinum Toxins, Type A / Q000008:administration & dosage* / Q000627:therapeutic use; D004305:Dose-Response Relationship, Drug; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007821:Laryngeal Muscles / Q000187:drug effects / Q000503:physiopathology; D008297:Male; D008666:Metalloendopeptidases / Q000008:administration & dosage* / Q000627:therapeutic use; D009119:Muscle Contraction / Q000187:drug effects; D009465:Neuromuscular Agents / Q000008:administration & dosage* / Q000627:therapeutic use; D016896:Treatment Outcome; D014832:Voice Disorders / Q000188:drug therapy* / Q000503:physiopathology
D009465:Neuromuscular Agents; C096323:rimabotulinumtoxinB; D008666:Metalloendopeptidases; D001905:Botulinum Toxins; D019274:Botulinum Toxins, Type A