The lowest effective dose of botulinum A toxin in adult patients with upper limb spasticity

Abstract

Objective: To define the lowest effective dose of botulinum toxin type A (Dysport®) and safety in the treatment of adult patients with upper limb spasticity. Design: This was a prospective, randomized, double-blind, dose-ranging study. Patients received either a placebo or one of three doses of Dysport® (350, 500, 1000 U) into five muscles of affected arm by anatomical and electromyography guidance. Efficacy was assessed periodically throughout the 6-month study period by the Modified Ashworth Scale (MAS), the Action Research Arm Test (ARA), the Barthel Index (BI) and the Visual Analogue Pain Scale (VAS). Results: Fifty patients were recruited. The four study groups were comparable at baseline with respect to their demographical characteristics and severity of spasticity. All doses of Dysport® studied showed a significant reduction from baseline of muscle tone and pain compared to placebo. However, the effect of functional disability was best at a dose of 500 U and the peak improvement was at week 8 after injection. A dose of 1000 U Dysport produced such an excess degree of muscle weakening that the number of randomized patients was reduced to five. BI and ARA of all patients were decrease after injection. No other adverse event was considered related to the study medication. Conclusion: This study suggests that treatment with Dysport® reduces muscle tone in adult patients with upper limb spasticity. The optimal dose for treatment of patients with residual voluntary movement in the upper limb appears to be 500 U.