A randomised, double-blind comparison of 20 units of onabotulinumtoxinA with 30 units of incobotulinumtoxinA for glabellar lines

Background : Biological activity data indicate that the units of incobotulinumtoxinA are not equivalent to those of onabotulinumtoxinA. Objective: This study compared 20 units of onabotulinumtoxinA with 30 units of incobotulinumtoxinA in the treatment of glabellar lines. Methods and materials : In this multicenter, randomised, double-blind study, subjects with moderate or severe glabellar lines received a single treatment with 20 units of onabotulinumtoxinA (n = 112), or 30 units of incobotulinumtoxinA (n = 112). The primary endpoint was the percentage of subjects with a reduction of >= 1 point on the Facial Wrinkle Scale at maximum contraction as rated by injectors on day 28 post injection. The same variable was evaluated on days 84, 98, and 112. Results: At the primary endpoint, 20 units of onabotulinumtoxinA was as effective as 30 units of incobotulinumtoxinA (96% vs. 95% responders, respectively; difference in proportion of responders = 0.02, 95% confi dence interval [CI] = 0.04, 0.07). At subsequent time points, a trend towards a higher percentage of responders was observed in the group treated with 20 units of onabotulinumtoxinA. Given that the 95% CI surpassed the upper equivalence margin at these time points, equivalence was not established. Conclusion: These data support the non-interchangeability of units of onabotulinumtoxinA and incobotulinumtoxinA, and the absence of a fixed dose ratio in clinical practice.