Eucerin impedes transdermal insulin delivery by sonophoresis in rats

The present study was designed to evaluate the effect of low-frequency ultrasound on transdermal delivery of insulin as an ointment. This was conducted in the proceeding of a previously published paper by the authors. Forty-two Wistar rats were randomly divided into 7 groups including one control and six experimental groups with six rats in each group. An ointment of insulin was prepared and applied (alone and with low-frequency ultrasound) on the skin of animals. In all the groups, blood samples were collected from the tail vein of the animals every 15 minutes of the whole 90-minute experimental period. The changes of blood glucose levels with time were assessed in the groups. The results of this study showed that the exposure of the insulin ointment to low-frequency ultrasound for a period of 60 minutes significantly decreased its potency in lowering the blood glucose levels. We conclude that eucerin impedes transdermal insulin delivery by sonophoresis in rats. We suggest that the lowering effect of ultrasound on the penetration ability of insulin is probably due to its effect on the specific molecular structure formed between the insulin and the ointment base after its preparation. However, further studies are needed in order to more precisely identify the involving mechanisms.