Evaluation of the injection force dynamics of a modified prefilled insulin pen.

Research paper by J J Rissler, C C Jørgensen, M M Rye Hansen, N-A NA Hansen

Indexed on: 20 Aug '08Published on: 20 Aug '08Published in: Expert opinion on pharmacotherapy


A modified version of the widely used pen FlexPen (FP), called Next Generation FlexPen (NGFP), has been designed to reduce the injection force with this pen. In this study, the injection force of NGFP was compared with another insulin pen, SoloStar (SS).The injection force of 24 pens of each type: NGFP fitted with a NovoFine 32G Tip ETW 6 mm needle; SS fitted with a NovoFine 32G Tip needle and SS fitted with a BD Micro-Fine 31G thin wall 5 mm needle, were tested during the delivery of 60 IU insulin at three constant push-button speeds - 4, 6 or 8 mm/s.NGFP had the lowest mean (+/- standard deviation) injection force at all injection speeds (8.3 +/- 0.6, 12.0 +/- 0.9 and 16.2 +/- 1.3 N at 4, 6 and 8 mm/s, respectively)--for SS fitted with a NovoFine 32G Tip needle the corresponding values were 10.2 +/- 1.1, 15.7 +/- 1.5 and 22.3 +/- 1.1 N, and for SS fitted with a BD Micro-Fine 31G needle they were 12.9 +/- 0.8, 20.5 +/- 1.3 and 29.6 +/- 1.9 N. This corresponded to an 18 - 45% lower injection force with NGFP. The time to complete each dose delivery (including the time manufacturers' recommend that the needle is left in situ after delivering the dose) was 14.2, 11.5 and 10.1 s with NGFP at injection speeds of 4, 6 and 8 mm/s, respectively, and were 16.4, 14.3 and 13.2 s with SS, respectively.This study shows that NGFP has a significantly lower injection force than SS at three specific push-button speeds.