Discussion regarding botulinum toxin, immunologic considerations with long-term repeated use, with emphasis on cosmetic applications. Minimal risk of antibody formation after aesthetic treatment with type a botulinum toxin.

Discussion regarding botulinum toxin, immunologic considerations with long-term repeated use, with emphasis on cosmetic applications.

Dose equivalence of two commercial preparations of botulinum neurotoxin type A: time for a reassessment?

BACKGROUND: The units of different preparations of botulinum neurotoxin type A (BoNT-A) have different potencies, and dosing recommendations for each product are not interchangeable. Historically, there has been debate concerning the dose-equivalence ratio that should be used in clinical practice. METHODS: Published evidence was considered to establish an appropriate dose-conversion ratio for the two main commercially available preparations of BoNT-A--Dysport (Dp) and Botox (Bx). RESULTS: Four key areas of evidence were identified: nonclinical and preclinical studies; studies exploring the diffusion characteristics and effects of complexing proteins; comparative experimental data from human studies; and clinical studies. Nonclinical data indicate that the principal reasons for differences in unit potency between the two products are dilution artefacts in the mouse assay. Use of saline as a diluent, at high dilutions, results in significant loss of potency in the Bx assay, whereas use of gelatin phosphate buffer in the Dp assay procedure protects the toxin during dilution. The published data on mouse assays show a Dp : Bx unit ratio range of 2.3-2.5 : 1 in saline and 1.8-3.2 : 1 in gelatin phosphate buffer. Data indicate that complexing proteins or size of the complex, which is highly pH sensitive, play no role in toxin diffusion and that Dp and Bx have similar diffusion characteristics when used at comparable doses. Randomized, controlled clinical studies indicate that 3 : 1 is more appropriate than 4 : 1, but the two products are not equivalent at this ratio. Comparative human experimental studies using the extensor digitorum brevis test, facial lines and anhidrotic action halo tests support dose-conversion ratios less than 3 : 1. LIMITATIONS: Data comparing dose equivalence ratios from the non-clinical setting should be extrapolated into the clinical setting with some caution. CONCLUSIONS: Dose-conversion ratios between Dp and Bx of 4 : 1 and greater are not supported by the recent literature.

Repeated botulinum toxin A injections for the treatment of lines in the upper face: a retrospective study of 4,103 treatments in 945 patients.

BACKGROUND: Although botulinum toxin type A (BoNT-A) is a common aesthetic intervention, there are few published data on treatment over more than two cycles. OBJECTIVE: To evaluate the effectiveness/safety of repeated doses of BoNT-A (Dysport, Ipsen Ltd., Slough, UK) in the upper face for reduction of wrinkles. METHODS: Retrospective, cross-sectional patient chart review from 945 patients who had received a minimum of three consecutive, documented treatment cycles. RESULTS: The glabella was treated most frequently (93.9%), with the majority (81.5%) of patients receiving treatment in more than one area of the face. BoNT-A treatments were combined with other aesthetic procedures in 57.5% of cases, mostly with fillers (37.1%). There was no evidence of tachyphylaxia: the dose applied, the interval between treatments, and satisfaction with the results remained stable over the course of treatment. Adverse events were those expected with BoNT-A treatment (most common: local bruising and ptosis) and were all mild or moderate in intensity. There was no sign of any cumulative adverse effects: indeed, the adverse-event rate decreased in later treatment cycles. CONCLUSIONS: Long-term, repeated injections of BoNT-A for corrections of wrinkles in the upper face yield a continuously high level of safety and effectiveness in actual practice.