Botox, Bocouture & Azzalure (Dysport) Conversion & Dilution: One Volume, Any Brand
The practical question is not which botulinum toxin — it is how to switch between them without changing your muscle. If Botox and Bocouture are reconstituted at 1 ml per 50 U, and Azzalure is reconstituted at 0.83 ml per 125 U, then 0.1 ml delivers the equivalent dose in every syringe. All you change is the vial. The volume — and therefore the technique — stays the same.
The conversion, in one line
1 unit Botox or Bocouture ≈ 3 Speywood units of Azzalure / Dysport. Some clinicians use 2.5:1; the 3:1 ratio is the working default at HSI because it maps cleanly onto the dilution protocol below. Speywood units and Allergan units are not the same currency — do not read one label with the other in your head.
Conversion Calculator
Educational tool. Confirm dose against product SmPC and your patient's clinical assessment before injecting.
Reconstitution: the mechanism of dilution
We dilute so that 0.1 ml is the working unit of thought. Azzalure 125 U reconstituted with 0.83 ml of saline gives 15 Speywood units per 0.1 ml. Botox or Bocouture 50 U reconstituted with 1.0 ml gives 5 units per 0.1 ml. Because 15 Speywood ≈ 5 Allergan (3:1), the same 0.1 ml delivers the equivalent clinical dose whichever brand is in the syringe.
In real practice a small volume is lost in the hub of the green (drawing-up) needle, so we round up the saline: 0.9 ml into Azzalure 125 U and 1.1 ml into Botox / Bocouture 50 U. The per-0.1 ml dose stays clinically equivalent, and the practitioner never has to convert at the bedside.
| Volume injected | Botox (U) | Bocouture / Xeomin (U) | Azzalure / Dysport (Speywood U) |
|---|---|---|---|
| 0.05 ml | 2.5 | 2.5 | 7.5 |
| 0.10 ml | 5.0 | 5.0 | 15.0 |
| 0.15 ml | 7.5 | 7.5 | 22.5 |
| 0.20 ml | 10.0 | 10.0 | 30.0 |
| 0.25 ml | 12.5 | 12.5 | 37.5 |
| 0.30 ml | 15.0 | 15.0 | 45.0 |
| 0.40 ml | 20.0 | 20.0 | 60.0 |
| 0.50 ml | 25.0 | 25.0 | 75.0 |
- 50 U vial
- Saline: 1 ml (rounded up for hub loss)
- Per 0.1 ml → 5 U
- 50 U vial
- Saline: 1 ml (rounded up for hub loss)
- Per 0.1 ml → 5 U
- 125 U vial
- Saline: 0.83 ml (rounded up for hub loss)
- Per 0.1 ml → 15 U
Why standardising volume, not units, is safer
When practitioners switch brands mid-list, the commonest error is a unit-to-unit mental substitution — treating 20 units of Azzalure as 20 units of Botox. Because Speywood units are roughly a third of Allergan units, that mistake either under-doses (Azzalure treated as Botox) or dangerously over-doses (Botox treated as Azzalure).
Fixing the arithmetic at the point of reconstitution makes injection technique brand-agnostic. The clinician thinks in volume. The equivalence lives in the vial, not in the practitioner's head.
Conversions apply to onabotulinumtoxinA (Botox), incobotulinumtoxinA (Bocouture / Xeomin) and abobotulinumtoxinA (Azzalure / Dysport) only. Daxibotulinumtoxin, prabotulinumtoxin and Chinese-manufactured toxins have separate potency profiles and are not interchangeable by this ratio.
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HSI Editorial Board · Reviewed for clinical accuracy · Not a substitute for the manufacturer's Summary of Product Characteristics.