A dosing unit of Botox is an arbitrary volume that makes a vial of 50 or 100 units a convenient amount for treating one or two cosmetic patients. (Botox patients in non-cosmetic indications generally need more than 100 units per treatment.)
A dosing unit of RT002 is also an arbitrary volume. The RT002 unit volume has not been calibrated to precisely match the amount of active toxin in 1 unit of Botox, but the amount of active toxin in 1 unit of RT002 is loosely similar to the amount in 1 unit of Botox.
The same applies to other brands of botulinum toxin such as Dysport and Xeomin.
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