title: Current evidence on the unit equivalence of different botulinum neurotoxin A formulations and recommendations for clinical practice in dermatology.
abstract: BACKGROUND
  The unit equivalence between the two main Botulinum neurotoxin A (BoNTA) preparations, Dysport (Ipsen Ltd., Slough, Berkshire, UK) and BOTOX (Allergan Inc., Irvine, CA), is a matter of discussion. The UK assay used to test Dysport is more sensitive than the U.S. assay used for BOTOX, resulting in a different efficacy per unit in both formulations. Ratios ranging from 6:1 to 1:1 can be found in the literature, but the more recently published literature suggests that 1 unit of BOTOX is equivalent to approximately 2 to 4 units of Dysport (ratio 2:1-4:1).
  
  
  OBJECTIVE
  Because the number of BoNTA treatments is constantly increasing, these differences warrant a systematic review of published evidence about the unit equivalence of UK and U.S. formulations.
  
  
  METHODS
  The review is based on a detailed literature research in all relevant databases (MEDLINE, PubMed, Cochrane Library, specialist textbooks).
  
  
  RESULTS
  The present review supports the recent assumption that dose ratios of less than 3:1 (e.g., 2.5:1 or even 2:1) between Dysport and BOTOX are probably more suitable.
  
  
  CONCLUSIONS
  The current evidence is still insufficient, and further investigation of lower dose ratios is recommended.
authors.affiliation: Laserklinik Karlsruhe, Karlsruhe, Germany.
authors.forename: Syrus
authors.initials: S
authors.lastname: Karsai
authors.forename: Christian
authors.initials: C
authors.lastname: Raulin
mesh_terms: D000818:Animals; D019274:Botulinum Toxins, Type A / Q000008:administration & dosage*; D006801:Humans; D006945:Hyperhidrosis / Q000188:drug therapy*; D009129:Muscle Tonus / Q000187:drug effects*; D012867:Skin / Q000187:drug effects*; D015595:Skin Aging / Q000187:drug effects
chemical_list: D019274:Botulinum Toxins, Type A