Botulinum toxin type B (Myobloc®) in subjects with hemifacial spasm: Results from an open‐label, dose‐escalation safety study

Ojbective Evaluate the safety of botulinum toxin type B (BoNT‐B) in subjects with hemifacial spasm (HFS). Methods This open‐label, sequential dose‐escalation study evaluated BoNT‐B in subjects with HFS. Eligible subjects were enrolled and received a single injection of one of four sequential BoNT‐B doses (100, 200, 400, or 800 U). Following injection, subjects were evaluated in person at Weeks 2 and 8 and by phone at Weeks 1, 4, and 10 and every 2 weeks thereafter until benefit was lost. Safety was assessed by adverse events (AEs), vital signs and clinical laboratory evaluation. The severity of HFS was assessed using a patient social impairment visual analog scale (VAS), subject severity of contraction VAS, the HFS physician assessment, and subject HFS frequency and severity assessment. Results Nineteen predominately Caucasian (92%) and female (67%) subjects (aged 36–80 years) with HFS participated in this study. Subjects remained in the study an average of 88 days (range of 41–332 days) after receiving a single dose of BoNT‐B. No deaths, serious AEs or AEs leading to trial discontinuation occurred during the study period. Two subjects in the 400 U dose group requested early withdrawal, whereas all other subjects completed the study. A reduction in HFS severity was observed in subjects treated with doses of 200 U or more. Improvements in subject HFS assessments tended to return to baseline values by 8 weeks following injection. Conclusion BoNT‐B was well‐tolerated and reduced HFS severity in subjects who received injections of 200 to 800 U. Additional investigation is necessary to confirm the findings from this open‐label study. © 2007 Movement Disorder Society