Comparisons among botulinum toxins: an evidence-based review.

BACKGROUND Botulinum neurotoxin treatment is the most common aesthetic procedure in the United States. A number of serotypes and formulations are available worldwide. Similarities and differences among these toxins were evaluated by reviewing the existing literature. METHODS Reports of botulinum neurotoxin for aesthetic use, published in peer-reviewed literature or presented at recent professional congresses, were reviewed to summarize key features of different toxins. Data from therapeutic uses in comparable anatomical areas were included in the review when aesthetic literature was limited. RESULTS Serotypes of neurotoxins share molecular structures and mechanisms of action but exhibit important differences between serotypes and between different formulations within the same serotype, including differences in distribution/diffusion patterns and risk/benefit profiles. The differences attributable to dissimilarities in bacterial strains, manufacturing techniques, and assays are likely to influence clinical performance. CONCLUSIONS Injection patterns, techniques, dilutions diffusion, and injection volumes established for a specific formulation of botulinum neurotoxin are not likely to be applicable to other formulations, and formulations are not interchangeable by any single conversion ratio. A large proportion of the clinical literature documents the aesthetic uses of the Allergan formulation of botulinum toxin type A. Additional studies are needed to establish optimal procedures for the Ipsen formulation and botulinum neurotoxin, and for diverse aesthetic uses.