A Comparison of Botox 100 U/mL and Dysport 100 U/mL Using Dose Conversion Ratio 1: 3 and 1: 1.7 in the Treatment of Cervical Dystonia: A Double-Blind, Randomized, Crossover Trial

Abstract

Objectives: 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).

Methods: 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.