Dose conversion ratio, comparative efficacy, and adverse events after switching from onabotulinum toxin A to abobotulinum toxin A for neurological conditions.

OBJECTIVES: Onabotulinum toxin A (ONA, Botox(R)) and abobotulinum toxin A (ABO, Dysport(R)) are most frequently used in the treatment of movement disorders. The aim of this study was to identify the dose conversion ratio (ABO dose:ONA dose), comparative efficacy, and adverse events in patients who switched from ONA to ABO. METHODS: There were 64 patients with cervical dystonia (39), hemifacial spasm (16), oromandibular dystonia (5), blepharospasm (3), and extremity dystonia (1) who switched from ONA to ABO. The efficacy, adverse events, duration of action, and severity of the adverse events after the final dose of ONA, initial dose of ABO, and second dose of ABO were investigated in these patients. RESULTS: The mean dose conversion ratio was 4.70 (2.27-9.62). The mean efficacy of the final ONA injection was 70.62%; initial ABO injection, 72.27%; and second ABO injection, 73.52%, which showed improvement on a visual analog scale (p = 0.71, p = 0.5). Incidence of adverse events after the final ONA injection was 18.8%; this increased to 39.1% after the initial ABO injection (p < 0.001) and decreased to 14.1% after the second ABO injection (p = 0.77). After the initial ABO injection, 20% of the adverse events were trivial, 36% were mild, and 32% were severe. After the second ABO injection, 7.8% of the adverse events were mild and 6.3% were severe. CONCLUSION: Although the mean dose conversion ratio was 4.70, the range was very wide (approximately 2-9). Therefore, we conclude that after the switch from Botox to Dysport, the doses should be tailored to the patients' clinical situation at treatment initiation, without using a dose conversion ratio.