Treatment and Clinical Management

It is important to note that the definition of a unit of activity varies among Botox, Dysport, and Myobloc. In clinical use, Botox appears three to four times stronger (in mouse units) than Dysport, and the dose must be adjusted accordingly [15]. Determining an equivalent unit of Myobloc is more complicated due to differences in such details as the vehicle, dilution scheme, and laboratory protocols for various assays (Table 5.4) [29].

Table 5.4. Comparison of Botox and Myobloc preparations       Botox   Myobloc   Preparation   Lyophilized powder in vials of 100 U   Liquid in vials of 2,500, 5,000, and 10,000 U   pH   7.2   5.5   Complex size   500–900 kDa   500–700 kDa   Specific potency   20 U/ng   100 U/ng   Stability   Approximately 4 h after reconstitution   2 years when stored at 4–8°C   Immunogenicity   Very low   Unknown