Prefilled insulin device with reduced injection force: patient perception and accuracy

The injection force and the patient perception of the Next Generation FlexPen (NGFP) with design modifications aimed at reducing injection force was assessed. The accuracy and precision of the NGFP was also tested under standard conditions.

Dosing accuracy was tested (according to ISO 11608 requirements) at 1 IU, 30 IU and 60 IU doses (acceptable limits were 1 +/- 1 IU (0-2 IU), 30 +/- 1.5 IU (28.5-31.5 IU), and 60 +/- 3 IU (57-63 IU)). Pens were tested at reference conditions (18-28 degrees C and relative humidity 25-75%). Delivered doses were measured on a sensitive balance and corrected for the specific density of the insulin aspart used (according to ISO 11608-1). Precision was calculated from the variance around the mean delivered dose. The injection force of NGFP was measured, and user-preference of NGFP and FlexPen (FP) were compared in 50 patients with type 2 diabetes.

The mean injection force with NGFP and FP was 12.57 +/- 1.81 N and 17.90 +/- 1.51 N (p<0.001), respectively. Almost twice as many patients rated the injection force as 'good' or 'very good' with NGFP (80%, 72% and 38% when delivering 20 IU, 40 IU and 60 IU, respectively) compared with FP (48%, 32% and 20% when delivering 20 IU, 40 IU and 60 IU, respectively) and 76% of patients rated NGFP as superior, in terms of simplicity and comfort, to FP. NGFP accurately delivered the set doses (means [SD] were 0.98 [0.06] IU, 29.98 [0.18] IU, and 59.93 [0.24] IU for the 1 IU, 30 IU and 60 IU doses, respectively).

These results show that NGFP has a 30% reduction in injection force compared with FP and was rated as 'more simple and comfortable to use' by patients. Furthermore, NGFP was as accurate and as precise as FP.