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Botox is the only FDA-approved botulinum toxin A, but a potential competitor, Dysport, has an FDA approval application pending. In this manufacturer-supported, double-blind, randomized, parallel-group study, the authors compared Dysport and Botox for the treatment of glabellar rhytids in 62 patients. The patients received either 20 total units of Botox or 50 total units of Dysport in their corrugator and procerus muscles and then underwent blinded assessments at maximal frown at 2, 8, 12, and 16 weeks after treatment.
Fifty-nine patients completed the study; none dropped out because of side effects or lack of efficacy. Efficacy peaked at 8 weeks in both groups, but by 12 weeks the Botox group showed greater residual effects. By 16 weeks, this difference was statistically significant: On a four-point wrinkle-severity scale, a one-point or better improvement occurred in 53% of Botox recipients and 28% of Dysport recipients. At week 16, 23% of Botox patients and 40% of Dysport patients had recurrence of rhytids. Patient satisfaction was consistently higher with Botox. Other than infrequent bruising and one small lump, there were no significant side effects.
Lowe P et al. Comparison of two formulations of botulinum toxin type A for the treatment of glabellar lines: A double-blind, randomized study. J Am Acad Dermatol 2006 Dec; 55:975-80.
Comment
At a 2.5:1.0 Dysport:Botox ratio, Botox was more effective for wrinkle treatment. In a previous study cited by the authors, a 4:1 ratio produced equivalent efficacy, but the patients receiving Dysport had a significantly higher risk for adverse effects. The evidence suggests that the optimal conversion ratio will be somewhere in between. Clearly, proper use of Dysport will involve a learning curve even for experienced Botox injectors, which will slow its wide adoption unless the cost difference significantly favors Dysport. In the U.K., where both products are approved, the cost of a 100-U vial of Botox is about $250, and the cost of a 500-U vial of Dysport is about $300. When Dysport receives FDA approval, the U.S. price may reflect the U.K. price.