Introduction: A new U.S. Botulinum toxin type A (BoNT-A) has been shown to be safe and effective when administered once, but there is a paucity of clinical evidence regarding long-term use.
Objective: To evaluate the long-term efficacy and tolerability of repeated treatment with BoNT-A in the correction of moderate-to-severe glabellar lines. STUDY DESIGN/METHODOLOGY: Multicenter, phase 3, randomized, placebo-controlled, double-blind study comparing the efficacy of BoNT-A (50 units) with placebo upon re-treatment of glabellar lines following two-to-three cycles of open-label BoNT-A treatment in 311 patients.
Results: At endpoint, BoNT-A produced a significantly higher proportion of responders versus placebo. The incidence of treatment-emergent adverse effects (TEAEs) was slightly lower during additional treatment cycles; the frequency was comparable between BoNT-A and placebo groups.
Conclusion: Multiple treatment cycles of BoNT-A were well tolerated in the majority of patients, and there was no tachyphylaxis seen during the study duration of up to 23 months.