Because the pharmacokinetics of three popular botulinum toxin products differ, there’s no shortcut to determining equivalent therapeutic doses, according to one expert.
Botox (onabotulinumtoxinA, Allergan) first earned Food and Drug Administration (FDA) approval in 1989. Dysport (abobotulinumtoxinA, Medicis) was approved in 2009. Xeomin (incobotulinumtoxinA, Merz) was FDA-approved in July 2010 for treatment of adults with cervical dystonia or blepharospasm.
Among FDA-approved products, “There’s no easy way to convert patients from one to the other. You can’t just multiply the Botox dosage by 2.5, put patients on Dysport and hope for the best,” says Kevin C. Smith, M.D., an Ontario-based dermatologist in private practice. “It’s not just a matter of the dose.” Because these products diffuse differently, achieving comparable results when switching from one drug to the other may require alteration in injection points, he explains.