What is the dose conversion formula from botulinum toxin type B (Myobloc®) to incobotulinum toxin type A (Xeomin®) or onabotulinum toxin type A (Botox®)?

There is not a set formula for converting from one formulation to another. In fact, each manufacturer warns against it. One possible guideline: Xeomin:Botox is 1:1. Dysport:Botox is 2.5-4:1 and Myobloc:Botox is 40-50:1. If I need to switch serotype, I would err on selecting a lower dose to start to ...

If a patient is maintained on 7,500-10,000 units of Myobloc then I typically would start patient on 200 units of Botox or Xeomin, or 500 units of Dysport. There is no standard conversion. Everyone use their own formula.