Engineering study comparing injection force and dose accuracy between two prefilled insulin injection pens

Abstract

Objective:This study compared injection force (measured by glide force [GF] and glide force variability [GFV]) and dosing accuracy of the Humalog KwikPen (prefilled insulin lispro [Humalog pen, Eli Lilly and Company, Indianapolis, IN) and the Next Generation FlexPen (prefilled insulin aspart [NovoRapid pen, Novo Nordisk A/S, Bagsværd, Denmark).* Humalog KwikPen is a registered trademark of Eli Lilly and Company, Indianapolis, IN, USA.† Humalog is a registered trademark of Eli Lilly and Company, Indianapolis, IN, USA.‡ FlexPen is a registered trademark of Novo Nordisk A/S, Bagsværd, Denmark.§ NovoRapid is a registered trademark of Novo Nordisk A/S, Bagsværd, Denmark.Research design and methods:A total of 100 prefilled insulin pens (50 insulin lispro pens, 50 insulin aspart pens) were tested using two dose sizes (30 U and 60 U). In all, 50 devices (25 of each type) were tested at 10 U/s dosing speed and 50 were tested at 6.6 U/s. Devices were used per manufacturer instructions. Dose accuracy (represented as absolute dose error %), maximum and average GF, and GFV data were automatically collected by the test system for all datasets (dose size/dosing speed/device type). The test system controlled for potential dosing errors.Results:The insulin lispro pen demonstrated a significantly lower median maximum GF at both dosing speeds: (2.83 vs. 3.92 lbs [30 U] and 3.00 vs. 4.14 lbs [60 U]) at 10 U/s; (1.85 vs. 2.93 lbs [30 U] and 2.14 vs. 3.02 lbs [60 U]) at 6.6 U/s, all p < 0.0001. For all datasets, the median GFV was significantly lower for the insulin lispro pen, p < 0.0001. Median dose error was comparable between device types when tested at 10 U/s dosing speed; however, at 6.6 U/s, the median dose error was significantly lower for insulin lispro pen compared to insulin aspart pen (0.47 vs. 0.67% [30 U] and 0.50 vs. 0.78% [60 U], both p < 0.05).Conclusions:The insulin lispro pen had significantly lower median GF and GFV compared with insulin aspart pen when tested at two dose sizes and two dosing speeds. Median dose error was similar between the device types at the 10 U/s dosing speed, but median dose error was significantly lower for the insulin lispro pen at the 6.6 U/s dosing speed. A limitation of this study was that it was executed as an open label study.