Respective potencies of Botox and Dysport: a double blind, randomised, crossover study in cervical dystonia
- Universitätsklinik für Neurologie, Universität Innsbruck, Anichstraβe 35, A-6020 Innsbruck, Austria
- Correspondence to: Dr W Poewe; Werner.Poewe{at}uibk.ac.at
Clinically appropriate conversion factor may be less than three
The issue of apparently different potencies of the two available formulations of botulinum toxin type A—Dysport and Botox—has continued to perplex clinicians for more than a decade. Empirically chosen doses expressed in mouse units in different series and different indications reported in the literature seemed to differ by factors of three to six.1,2 To date only two randomised controlled studies have tried to answer the question of what the correct conversion factor yielding bioequivalence should be. One was conducted in previously untreated patients with blepharospasm or hemifacial spasm and found a bioequivalence ratio of Botox to Dysport of 1:4 with duration of effect as …
