Novo Nordisk's FlexiPen has proved its superiority over SoloStar, from Sanofi-Aventis, according to two independent studies.

FlexPen is more accurate when delivering insulin than other pens like the newly launched prefilled device, SoloStar, from Sanofi-Aventis, which FlexPen significantly outperformed in both studies, according to a Novo Nordisk company release.

The two studies were lead by Prof Andreas Pfützner from IKFE, Institute for Clinical Research and Development in Germany, and Dr Toshinari Asakura from the Niigata University of Pharmacy and Applied Life Sciences in Japan. The German study was published in the May 2008 issue of Diabetes Science and Technology.

"We were surprised to see great dose deviations between the different pens. Accurate insulin doses are essential to keep diabetes in good control and to avoid serious side effects, and in the longer perspective, to avoid complications deriving from the disease. In patients sensitive to insulin, even small deviations can have a great impact on the patients' daily lives. Therefore, it is important that the insulin devices are accurate," says Prof Pfützner, Institute for Clinical Research and Development, Mainz, Germany, who has been heading up the German study.

Study findings. In both studies, acceptable limits for dose accuracy were based on International Organization for Standardization (ISO) definitions of ±1 IU for a 10 IU dose, and ±1.5 IU for a 30 IU dose.

The German study tested the pens at two doses (10IU and 30IU). At both doses measured, Levemir FlexPen accurately delivered volumes of insulin with fewer deviations than Lantus SoloStar.

"These are important findings. Even a relatively small deviation of 3 units can have quite an effect, especially for patients who are requiring low doses of insulin, like children and adults with type 1 diabetes. The findings of these accuracy studies should therefore be taken into account by doctors when choosing insulin and device, especially for patients who are sensitive to insulin," stated Prof Pfützner.

In the Japanese study led by Dr Asakura, the German findings were confirmed. Results demonstrated significantly fewer deviations from the set dose with Levemir FlexPen than with Lantus SoloStar at three different doses (5IU, 10IU and 30IU) tested in the study. Combining all measured doses showed that only 0.4 per cent of the doses delivered by FlexPen were outside the specified limits whereas 14.5 per cent of doses delivered by SoloStar were outside specified limits.

In both studies, the insulin pens were prefilled with their respective brands of insulin: Levemir (insulin detemir) (FlexPen); Lantus (insulin glargine) (SoloStar).