title: Trigger matters: an ergonomy analysis of insulin pens.
abstract: BACKGROUND
  Excessive force required to deliver a set dose of insulin as well as a localization of the push button and its upwards extension may result in significant difficulties to safely perform insulin injection, including bending/breakage of the injector's needle. The GensuPen2 (Copernicus/Bioton, Warsaw, Poland) pen has a unique spring-assisted delivery system and a lateral trigger device for injection of insulin to improve its ergonomics. We tested the force required to administer insulin using three pens: GensuPen2, NovoPen(®) 4 (Novo Nordisk, Bagsværd, Denmark), and HumaPen Ergo(®) (Eli Lilly, Indianapolis, IN).
  
  
  METHODS
  Using a certified dynamometer we tested injection force at three doses of insulin: 2, 30, and 60 U, using each of the three injectors (n=10) in triplicate. Area under the curve (AUC) and maximum force used were calculated for each series of injections.
  
  
  RESULTS
  When administering doses of 2, 30, and 60 units of insulin, the GensuPen2 (6.55±1.09, 6.52±1.92, and 6.89±1.15 N, respectively) required significantly lower maximum force than the NovoPen 4 (9.04±0.61, 12.96±1.45, and 15.42±0.99 N, respectively) and the HumaPen Ergo (17.66±1.88, 32.14±6.08, and 40.39±7.64 N, respectively) (all P<0.0001). The AUC of force used for insulin injection with GensuPen2 did not differ between doses (P=0.82). At all dose levels, GensuPen2 required significantly lower force than the other two injectors. Moreover, the mode of holding of GensuPen2 was more similar to the natural arrangement of the hand while gripping a cylindrical item in comparison with NovoPen 4 and HumaPen Ergo.
  
  
  CONCLUSIONS
  Usage of the GensuPen2 injector with a lateral trigger location and spring-assisted delivery system reduces the force required for drug administration, especially at high doses of insulin.
authors.affiliation: 1 Department of Pediatrics, Oncology, Hematology & Diabetology, Medical University of Lodz , Lodz, Poland .
authors.forename: Wojciech
authors.initials: W
authors.lastname: Fendler
authors.forename: Danuta
authors.initials: D
authors.lastname: Roman-Liu
authors.forename: Tomasz
authors.initials: T
authors.lastname: Tokarski
authors.forename: Radoslaw
authors.initials: R
authors.lastname: Romanczuk
authors.forename: Wojciech
authors.initials: W
authors.lastname: Mlynarski
mesh_terms: D003920:Diabetes Mellitus / Q000188:drug therapy; D004867:Equipment Design; D018737:Hand Strength; D006801:Humans; D007004:Hypoglycemic Agents / Q000008:administration & dosage*; D007279:Injections, Subcutaneous / Q000295:instrumentation; D007328:Insulin / Q000008:administration & dosage*; D008328:Man-Machine Systems; D009339:Needles / Q000592:standards; D013594:Syringes
chemical_list: D007004:Hypoglycemic Agents; D007328:Insulin