In making comparisons of BoNT brands and serotypes, it is important to understand the concept of BoNT dose in mouse units (mu). The mouse lethality assay is a biologic assay used to define the activity of BoNT. The potency of BoNT is indicated as mouse units. One mouse unit is defined as the amount of BoNT required to kill 50% (LD50) of a certain weight, strain, and sex of mice.^[4] Although it is well defined, potency as defined by this biologic assay may vary from one particular test system to another.^[5] Hence, it is not surprising that dosages of botulinum toxin may vary depending on the preparation of the toxin. For the three brands of serotype A commercially available, doses of Botox for cervical dystonia (CD) range from 100 to 300 U per injection series,^[6] Xeomin appears to have the same dose range as Botox,^[7] and Dysport dosing ranges from 500 to 1000 U.^[8]Not surprisingly given the basic differences among serotypes, the dosing of BoNT/B as …