Background: Different formulations of botulinum toxin type A (BoNTA) may have different diffusion characteristics.
Objective: The objective was to compare the diffusion characteristics of two formulations of BoNTA.
Materials and methods: A total of 20 patients with forehead hyperhidrosis received four injections of BoNTA in their forehead (one medial and lateral injection of one formulation randomly assigned to one forehead side, one medial and lateral injection of the other formulation to the other forehead side). Patients received 3 U/injection of BoNTA(1) (BOTOX, Allergan, Inc.) and were randomly assigned to receive BoNTA(2) (Dysport, Ipsen Ltd.) at a dose ratio of 1:2.5, 1:3, or 1:4. The area of anhidrosis was highlighted using iodine and starch and determined by software from standardized photography.
Results: During the 6 months after treatment, the area of anhidrosis was larger with BoNTA(2) in 93% (195/210) of medial-medial or lateral-lateral comparisons of the two products and at all dose ratios. The smaller area of anhidrosis with BoNTA(1) did not compromise its efficacy in inhibiting contraction of frontalis muscle.
Conclusion: BoNTA(2) has a greater area of diffusion in the forehead than BoNTA(1), even with identical injection volumes. This may hinder accurate localization of clinical effect, thereby increasing the potential for adverse effects.