Study on the Dosing Accuracy of Commonly Used Disposable Insulin Pens

Background: Improved patient comfort and optimal glycemic control have led to the widespread use of insulin pens, particularly in Europe. Most of the former studies on the dose accuracy of insulin pens included only a small number of doses and pens. In extension to our previous large-scale study testing the dosing accuracy following a randomized dosing sequence with each pen, the present study was more directed toward the dose accuracy for one specific dose dispensed repeatedly with the same pen. This is the first study providing detailed comparative data on the accuracy of repeated dose delivery with prefilled disposable insulin pens at low, middle, and high doses, dispensed over the entire pen volume. Materials and Methods: In total, 15 previously unused insulin pens from two lots of each pen type (SoloSTAR (R) [sanofi-aventis, Paris, France], FlexPen (R) [Novo Nordisk A/S, Bagsvaerd, Denmark], Next Generation FlexPen [Novo Nordisk], and KwikPen (TM) [Eli Lilly, Indianapolis, IN]) were used to deliver 5-unit (low), 30-unit (middle), and 60-unit (high) doses, respectively, dispensed four times from each pen in a nonrandomized manner. Actual doses were determined gravimetrically taking the density of the respective insulin into account and were evaluated according to the guidelines (DIN EN ISO 116081: 2000) of the International Organization for Standardization (ISO). Results: All tested insulin pens met the requirements for accuracy with none of the single values being outside the defined range of the ISO recommendations (1 +/- 1 units, 30 +/- 1.5 units, and 60 +/- 3 units, respectively). Conclusion: The present study demonstrated a consistent and accurate dose delivery at all dosage levels for all tested insulin pens, with no clinically relevant differences among the products.