Objective: Different formulations of botulinum toxin type A (BoNTA) are not identical and may behave differently in clinical practice. The reportedly lower incidence of adverse effects with one formulation (from Allergan, Ltd.) relative to another (from Ipsen, Ltd.) may be due to differences in the degree of migration of the neurotoxin-protein complex from its injection site. A double-blind, randomized, within-subject pilot study was performed to compare the migration characteristics of each formulation.
Methods: Twelve healthy volunteers were randomly assigned to receive three 0.1 mL intradermal injections in their forehead: 4 U BoNTA (Allergan) on one side, 12 U BoNTA (Ipsen) on the contralateral side, and saline in the center. At day 14, Minor's iodine starch test was performed, and the subjects walked around a hot room to induce sweating. The appearance of each forehead was documented using Canfield photography and the area of each anhidrotic halo calculated using software.
Results: Overall, the area of anhidrosis was significantly larger with BoNTA (Ipsen) than BoNTA (Allergan) - mean +/- SD of 2.7 +/- 0.78 cm(2) vs. 1.8 +/- 0.65 cm(2) (P = 0.005) - with the area of anhidrosis being greater with BoNTA (Ipsen) than BoNTA (Allergan) in 11 of the 12 subjects. Across all subjects, the area of anhidrosis was greater with BoNTA (Ipsen) than BoNTA (Allergan) by a mean of 77%.
Conclusions: BoNTA (Ipsen) migrates more than BoNTA (Allergan) under the conditions described. The lower potential of BoNTA (Allergan) to migrate promotes more precise localization of clinical effects, thereby helping to optimize the risk/benefit ratio.