A double blind, randomised, parallel group study to investigate the dose equivalence of Dysport® and Botox®in the treatment of cervical dystonia

OBJECTIVE This study was designed to establish whether a ratio of three units of Dysport® is equivalent to one unit of Botox® for the treatment of cervical dystonia. METHODS Patients with predominantly rotational cervical dystonia, and a minimum of four previous Botox treatments, were randomised to receive either the clinically indicated dose of Botox or three times that dose in Dysport units. Study botulinum toxin was administered in a double blind fashion, to one or more clinically indicated muscles, at one or more sites per muscle. Patients returned for assessment two, four, eight, and 12 weeks after treatment. RESULTS A total of 73 patients (Dysport, 38; Botox, 35) were entered. The Dysport group received a mean (SD) dose of 477 (131) (range 240–720) Dysport units, and the Botox group received a mean (SD) dose of 152 (45) (range 70–240) Botox units. The mean (SEM) post-treatment Tsui scores for the Dysport group (4.8 (0.3)) and the Botox group (5.0 (0.3)) were not statistically different (p=0.66). The study had 91% power to detect a clinically significant difference of two points. Both groups showed substantial improvement in Tsui score by week 2 (mean (SD); Dysport, 46 (28)%; Botox, 37 (28)%), with a peak effect at week 4 (mean (SD); Dysport, 49 (29)%; Botox, 44 (28)%). A similar response profile was seen for other assessments of efficacy. The duration of effect, assessed by time to retreatment, was also similar (mean (SD); Dysport, 83.9 (13.6) days; Botox, 80.7 (14.4) days; p=0.85). During the study 22 of 38 (58%) Dysport patients reported 39 adverse events, and 24 of 35 (69%) Botox patients reported 56 adverse events (p=0.35). A global assessment of efficacy and safety considered that 29 of 38 (76%) Dysport patients and 23 of 35 (66%) Botox patients were treatment successes (p=0.32). CONCLUSION Patients with predominantly rotational cervical dystonia treated with the clinically indicated dose of Botox or three times that dose in Dysport units show similar improvements and do not have significantly different safety profiles.