Azzalure and Speywood units (abobotulinumtoxinA)
The preparation measured in Speywood units — a unit system unique to abobotulinumtoxinA products and convertible to no other.
Azzalure is a preparation of botulinum toxin type A, international non-proprietary name abobotulinumtoxinA. In the UK it is supplied as a powder for solution for injection in a 125 Speywood unit vial.
The same active substance is marketed under other brand names for other indications — Dysport being the best known — and the UK product information for every botulinum toxin type A product is indexed on the electronic medicines compendium.
Speywood units
This is the point that causes the most trouble in practice. Potency here is expressed in Speywood units, a system defined by the manufacturer’s own assay and specific to abobotulinumtoxinA.
A Speywood unit is not equivalent to an Allergan Unit, nor to a Bocouture unit. The SmPC states that units are not interchangeable between products, and no conversion factor between unit systems is licensed.
This matters because ratios do circulate — in training material, on forums, in conversation between practitioners. They are not approved, they are not consistent between sources, and treating one as authoritative means dosing a prescription-only medicine on the basis of hearsay. The correct reference for any product is that product’s own SmPC.
On “converting to insulin units”
A related question appears frequently: whether product units can be read off an insulin syringe. They cannot be equated. An insulin syringe is graduated in volume — its “units” are marks on a barrel, a measure of how much liquid it holds. Product potency is a measure of biological activity, and the relationship between the two depends entirely on how the vial was reconstituted.
Volume markings and potency units are different quantities. Conflating them is a dosing error, not a shortcut.
Dose and reconstitution
Set by the manufacturer and published in the SmPC, linked below. This page does not restate them.
This page is a reference note. It carries no dose, no injection points and no dilution figures: those are set by the manufacturer and published in the Summary of Product Characteristics, which is linked below. This site sells nothing and is not a clinic.
