Intramuscular injections of botulinum toxin (BTX) are used as symptomatic treatment for cervical dystonia. Botox and Dysport are commercial products containing BTX; however, dosage and concentration of the prepared solution vary considerably among studies. The concentration of BTX in the prepared solution affects clinical outcome. This double-blind, randomized crossover trial compares Botox and Dysport in 2 different dose conversion ratios (1:3 and 1:1.7) when diluted to the same concentration (100 U/mL).
Forty-six patients with cervical dystonia received 3 different treatments, Botox in 2 different doses and Dysport as control treatment. The efficacy was evaluated 4 and 12 weeks after treatment using 5 instruments, including Toronto Western Spasmodic Torticollis Rating Scale.
Results and Conclusion
The primary outcome was the estimated median Toronto Western Spasmodic Torticollis Rating Scale total score, which was 1.96 points higher for Botox (1:3) compared with Dysport at week 4, but the difference was not statistically significant (confidence interval, −0.88–4.61; P = 0.0799). No significant differences were seen between Botox (1:1.7) and Dysport. At week 12, a statistically significant difference in effect between Botox (1:3) and Dysport was observed, suggesting a shorter duration of effect for Botox when this ratio (low dose) was used. Furthermore, the patients' assessments showed that the ratio 1:3 resulted in suboptimal efficacy of Botox. These secondary outcome observations indicate that the dose conversion ratio between Dysport 100 U/mL and Botox 100 U/mL may be lower than 1:3, but this must be further validated in a larger patient material.