Purpose: Transdermal insulin delivery is an attractive needle-free alternative to subcutaneous injection conventionally used to treat diabetes. However, skin's barrier properties prevent insulin permeation at useful levels.
Methods: We investigated whether microdermabrasion can selectively remove skin's surface layers to increase skin permeability as a method to administer insulin to diabetic rats. We further assessed the relative roles of stratum corneum and viable epidermis as barriers to insulin delivery.
Results: Pretreatment of skin with microdermabrasion to selectively remove stratum corneum did not have a significant effect on insulin delivery or reduction in blood glucose level (BGL). Removal of full epidermis by microdermabrasion significantly reduced BGL, similar to the positive control involving subcutaneous injection of 0.1U insulin. Significant pharmacokinetic differences between microdermabrasion and subcutaneous injection were faster time to peak insulin concentration after injection and larger peak insulin concentration and area-under-the-curve after microdermabrasion.
Conclusions: Microdermabrasion can increase skin permeability to insulin at levels sufficient to reduce BGL. Viable epidermis is a barrier to insulin delivery such that removal of full epidermis enables significantly more insulin delivery than removal of stratum corneum alone.