What’s new in neurotoxins

Kohala Coast, HI

- With new botulinum toxin products on the horizon and perhaps more to follow from Asian manufacturers, questions are arising about possible differences between these agents and how they should be used.

Addressing these issues at the Winter Clinical Dermatology Conference, Richard G. Glogau, M.D., mentioned the parable of blind men describing an elephant and also used the analogy of learning new languages. He explained different botulinum toxin preparations can be distinguished by differences in serotype, structure of the complexes, and other aspects of the formulation, such as pH and excipient content. However, whether any of these features affects biologic behavior and clinical outcomes is still unclear.

"You’re going to be told a story, each of which attempts to make sense of observed phenomena relating to the different neurotoxins. Keep your mind open and try to make sense of which portions of the stories make utilitarian sense for you," Dr. Glogau said.

He also suggested that clinicians might consider Botox Cosmetic (botulinum toxin type A, Allergan) their primary language, but he proposed that they learn to become "fluent" with alternatives, albeit perhaps with some minor modifications in technique.

"Botox Cosmetic remains the benchmark product in our hands. But, my prediction is clinicians will wind up making additions to their neurotoxin ‘language’ over time," said Dr. Glogau.

"Incorporating new botulinum toxin products into our armamentarium will be like an English-speaking person learning Spanish and then learn French. You can learn both new languages equally well, but after first acquiring skill with one, there is a learning curve and some extra skills to develop before gaining fluency with the next. At the end of the day, you can take them both to the same level."

Relative evaluations of different products are also made difficult by a lack of comprehensive overviews and direct comparative studies. There are good comparative studies of different botulinum toxin preparations for treatment of blepharospasm and some data from studies investigating diffusion based on muscle movement and anhidrosis assessment, although the relevance of some of the findings to the cosmetic applications of botulinum toxin are uncertain, and other questions about the results remain.

Dr. Glogau said there will not be changes to the basic botulinum toxin type A molecule in the near future or any increase in the duration of the botulinum toxin effect. However, clinicians can anticipate changes in marketing as the competition increases.

Dr. Glogau also cautioned clinicians to avoid being tempted by letters of solicitation from agents selling foreign products at a low cost.

"Don’t under any circumstances, purchase, use or distribute material that is not FDA approved. Either turn the letter over the FDA or throw it away," he said.DT