A promising means of insulin delivery
Alternative insulin delivery concepts focus on reducing the pain of injection and finding faster routes for insulin absorption. A number of these concepts have focused on the skin, which has the potential for higher absorption rates for insulin because it has greater vascularity than the subcutaneous tissue.
Profil has conducted clinical trials on insulin injection into the skin via microneedles that are 1–2 mm long. Another interesting approach that is currently in the latest stages of preclinical development is a transdermal patches lined with arrays of insulin-loaded microneedles that dissolve upon insertion. If the rate of the dissolving insulin can be kept relatively constant over time, such insulin patches could be the foundation of needle-free basal insulin therapy.
Until now, clinical research with intradermal insulin administration has focused on demonstrating improvements in the speed of insulin absorption and postprandial glucose excursions. The overall relative bioavailability of intradermal insulin is comparable to that of subcutaneous insulin, but faster and higher absorption of the intradermal insulin gives it the desired ‘faster-in, faster-out’ profile. Using this means of insulin delivery, maximum insulin concentrations are more pronounced and are reached approximately 20 minutes earlier than after subcutaneous injection of the same rapid-acting insulin analogue.
In clamp and meal studies, the faster insulin absorption also resulted in significant differences in the glucose-lowering effect, showing promise that intradermal application may be at least as efficacious as subcutaneous insulin in larger comparative clinical studies. The potential reduction in intra- and intersubject variability with intradermal insulin could contribute to achieving a highly effective therapeutic option, and even reduce the risk of hypoglycemia.
It is exciting to note that the first clinical studies with a continuous intradermal insulin infusion via an insulin pump and microneedle have demonstrated the feasibility of this approach.