Electrically enhanced transdermal delivery of insulin to chronic diabetic rats

Passive and electrically-enhanced iontophoretic transdermal delivery of insulin was compared. The effect of skin preparation on efficacy of transdermal delivery was also studied. Twenty diabetic rats were shaved before the study, and some groups had stubble removed using depilatory lotion. The iontophoretic drug electrode was filled with insulin and adhered to the abdomen of the rat. Experimental results were quantified by monitoring blood glucose levels (BGL). When insulin was placed on the shaved skin, BGL fell in the diabetic rat. In general, glucose levels fell more quickly and more profoundly using electrical enhancement. However, some skin preparations facilitated the movement of insulin. The most profound effect of lowered BGL occurred when depilatory lotion was used on the day of the study in conjunction with iontophoresis, where BGL fell by 61% after one hour. Passive insulin delivery with same-day depilatory treatment showed that BGL fell by 29% after one hour. When no depilatory was applied, or when the depilatory was applied 24 hours before the study, BGL did not vary significantly (p<0.05) from control results. Experimental evidence indicates a substantial increase in penetration of insulin with the same-day application of a depilatory in conjunction with iontophoretic enhancement.