Recommendations for the best possible use of botulinum neurotoxin type a (Speywood units) for aesthetic applications.

The botulinum neurotoxin (BoNT) product Azzalure (manufactured by Ipsen Biopharm Limited, Wrexham, UK; distributed by Galderma), measured in Speywood units (s.U) has been available since 2009 for temporary improvement in the appearance of moderate to severe glabellar lines. Although we know much about the use of Azzalure for aesthetic indications, some aspects of product use in the clinic still require an update based on continuing and prevailing misconceptions and new clinical data. Therefore, a group of experts experienced with the use of Azzalure convened to formulate the following recommendations: (1) The key to an optimal effect is adequate dosing per injection point. Ten s.U are indicated for strong muscular activity, 5 s.U for medium activity, and approximately 2 s.U for minor activity. (2) The main factor that influences the area of effectiveness is the dosage per injection point. (3) In contrast to former beliefs, we know now that Azzalure works very fast, with some patients reporting initial drug activity after hours. (4) Various volumes can be used for dilution. However, the first choice is the recommended volume, 0.63 mL per vial of 125 s.U. Nevertheless, for clinicians changing products, keeping the volume they are used to might be an option. (5) Clinicians changing products have to be very careful not to confuse the units between different products. (6) In aesthetic BoNT-A usage, the development of antibodies is very rare and is not the common reason for insufficient results. (7) Probably the most common reason when BoNT-A is not working is the absolute or relative underdosage. The present adjunctive recommendations elaborated in an informal expert meeting should help physicians to optimize their treatment with Speywood unit products.