Pharmacology of botulinum neurotoxin type A

The efficacies and potencies of Dysport and Botox, botulinum neurotoxin type A complexes approved for therapy, were investigated under various conditions. Conditions for maximal expression of biological activities of both commercial products were explored in vitro in the phrenic nerve-hemidiaphragm preparation whilst conditions for optimal distribution of Dysport were tested in vivo in a double blind trial involving volunteers, using the foot Muscles extensor digitorum brevis. Whilst Dysport and Botox expressed the same potency in vitro when albumin was added, their potencies markedly departed from each other when the products were reconstituted as recommended by the manufacturer. The biological availability of Dysport could be enhanced in vivo by (1) lowering its concentration, (2) supplementing with albumin and (3) increasing the injection volume. Thus, Dysport can be recovered more efficiently by deviating from the manufacturer's recommendations allowing a more economical use of Dysport.