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Botulinum toxin A and B: a comparative dosing study for spasmodic dysphonia.
1College of Physicians and Surgeons, Columbia University, New York Center for Voice and Swallowing Disorders, New York, NY 10019, USA. AB1136@aol.com
Summary
This study determined a conversion factor of 52.3 units of Myobloc (BTX-B) to 1 unit of Botox (BTX-A) for treating spasmodic dysphonia. Myobloc offers a safe and effective alternative with a faster onset but shorter duration.
Area of Science:
- Neurology
- Pharmacology
- Otolaryngology
Background:
- Adductor spasmodic dysphonia (AdSD) is a debilitating voice disorder.
- Botulinum neurotoxin type A (BTX-A) is a standard treatment for AdSD.
- Exploring alternatives like botulinum neurotoxin type B (BTX-B) is crucial for patient management.
Purpose of the Study:
- To establish the conversion factor between BTX-A and BTX-B for laryngeal muscle injection.
- To evaluate the safety and efficacy of BTX-B as an alternative to BTX-A in AdSD patients.
Main Methods:
- A prospective study involving 32 patients with AdSD.
- Patients transitioned from stable BTX-A doses to BTX-B at a 50 U:1 U conversion ratio.
- Dosing was adjusted over a 1-year follow-up period based on patient response.
Main Results:
- The determined conversion factor was 52.3 U of BTX-B to 1 U of BTX-A.
- BTX-B demonstrated a significantly faster onset of action (2.09 days vs. 3.2 days; P=0.028).
- BTX-B had a shorter duration of benefit (10.8 weeks vs. 17 weeks; P=0.002), with similar safety profiles. Dry mouth was reported in 3 patients on Myobloc.
Conclusions:
- A conversion factor of 52.3:1 (BTX-B:BTX-A) is established for treating AdSD.
- Myobloc (BTX-B) is an effective alternative treatment for patients with spasmodic dysphonia.
- The findings support individualized treatment adjustments based on BTX-B's distinct pharmacokinetic profile.