The beneficial antispasticity effect of botulinum toxin type A is maintained after repeated treatment cycles

Objective: To study the efficacy, safety, and incidence of BtxA antibody formation with repeated treatments with BtxA in post-stroke upper limb muscle spasticity. Methods: The study was a prospective open label trial. Patients with established post-stroke upper limb spasticity received 1000 units of BtxA (Dysport) into five muscles of the affected arm on study entry. Treatment was repeated every 12, 16, or 20 weeks as clinically indicated. Each patient received a total of three treatment cycles. Efficacy of treatment was assessed using the Modified Ashworth Scale. Patients were assessed on study entry and on week 4 and 12 of each treatment cycle for all safety and efficacy parameters. Blood samples for BtxA antibody assay were taken at baseline and on completion of the trial. Results: Fifty one patients were recruited and 41 of them completed the study. Improvement from the cycle one baseline was observed in all the outcome measures. Mild to moderately severe treatment related adverse events were reported in 24% of cases. There were no serious adverse events. No BtxA antibodies were detected. Conclusion: BtxA at a dose of 1000 units Dysport was efficacious in the symptomatic treatment of post-stroke upper limb spasticity. The study suggests that this effect can be maintained with repeated injections for up to at least three treatment cycles, with duration of effect per cycle of between 12 and 20 weeks. BtxA was safe in the dose used in this study and did not induce the formation of detectable levels of neutralising BtxA antibodies.