title: Insulin leakage value in relation to pen needle length and administered dose after subcutaneous injection.
abstract: OBJECTIVE
  During a subcutaneous injection with commonly used pen needles, the safety of drug administration plays an essential role. Today short needles with a length of 5.0 mm are increasingly being used. However, so far it is unresolved whether short needles of <5.0 mm affect the safety of insulin injections because of an increased backflow to the skin surface. We examined the influence of needle length and administered insulin dosage on the insulin backflow and the distribution of human insulin in the tissue by a quantitative determination of the amount of backflow of insulin to the skin surface. For the first time a new 4.5-mm pen needle was examined for its administration safety.
  
  
  METHODS
  Human insulin was radioactively marked. By means of an insulin pen different insulin dosages with pen needles of different lengths into fresh pork rind (ex vivo model) were administered. The amount of the marked insulin leaking from the tissues at the injection site was covered and absorbed immediately into a cotton swab. The amount of leakage was calculated by means of the radioactivity taken up by the swab.
  
  
  RESULTS
  The amount of leakage for each measurement was less than 1% of the total dosage administered. The amount of leakage increased with increased dosage administered in absolute terms, but expressed as a percentage of the increased dosage administered the leakage decreased.
  
  
  CONCLUSIONS
  The needle length (between 12 mm and 4.5 mm) did not have a meaningful influence on the amount of leakage; however, significant differences with different needle lengths could be observed.
authors.affiliation: Department for Safety Engineering, Occupational Health and Infection Control, University of Wuppertal, Wuppertal, Germany. andwitt@uni-wuppertal.de
authors.forename: Andreas
authors.initials: A
authors.lastname: Wittmann
authors.forename: Jan
authors.initials: J
authors.lastname: Köver
authors.forename: Nenad
authors.initials: N
authors.lastname: Kralj
authors.forename: Klaus
authors.initials: K
authors.lastname: Gasthaus
authors.forename: Hartmut
authors.initials: H
authors.lastname: Lerch
authors.forename: Marc
authors.initials: M
authors.lastname: Rommel
authors.forename: Susanne
authors.initials: S
authors.lastname: Moses
authors.forename: Friedrich
authors.initials: F
authors.lastname: Hofmann
mesh_terms: D006801:Humans; D007279:Injections, Subcutaneous / Q000295:instrumentation*; D007328:Insulin / Q000008:administration & dosage*; D009339:Needles
chemical_list: D007328:Insulin