ACCURACY AND REPRODUCIBILITY OF LOW-DOSE INSULIN ADMINISTRATION USINGPEN-INJECTORS AND SYRINGES

Many children with diabetes require small doses of insulin administere d with syringes or pen-injector devices (at the Booth Hall Paediatric Diabetic Clinic, 20% of children aged 0-5 years receive 1-2 U insulin doses). To determine how accurately and reproducibly small doses are d elivered, 1, 2, 5, and 10 U doses of soluble insulin (100 U/ml) were d ispensed in random order 15 times from five new NovoPens (1.5 mi), fiv e ED-Pens (1.5 mi), and by five nurses using 30 U syringes. Each dose was weighed, and intended and actual doses compared. The two pen-injec tors delivered less insulin than syringes, differences being inversely proportional to dose. For 1 U (mean (SD)): 0.89 (0.04) U (NovoPen), 0 .92 (0.03) U (BD-Pen), 1.23 (0.09)U (syringe); and for 10 U: 9.8 (0.1) U (NovoPen), 9.9 (0.1)U (ED-Pen), 10.1 (0.1)U (syringe). The accuracy (percentage errors) of the pen-injectors was similar and more accurat e than syringes delivering 1, 2, and 5 U of insulin. Errors for 1 U: 1 1(4)% (NovoPen), 8(3)% (BD-Pen), 23(9)% (syringe). The reproducibility (coefficient of variation) of actual doses was similar (< 7%) for all three devices, which were equally consistent at underdosing (pen-inje ctors) or overdosing (syringes) insulin. All three devices, especially syringes, are unacceptably inaccurate when delivering 1 U doses of in sulin. Patients on low doses need to be educated that their dose may a lter when they transfer from one device to another.