Transdermal Drug Delivery of Insulin with Ultradeformable Carriers

For a long time, scientists believed that macromolecules can only be introduced through the skin with a hypodermic needle or some other harsh treatment that locally damages the skin barrier. It is now clear that macromolecules can be administered epicutaneously, so that insulin, for example, can exhibit therapeutic effects in patients with type 1 diabetes mellitus. When carriers are employed for the purpose, the drugs must be associated with specifically designed vehicles in the form of highly deformable aggregates and applied on the skin non-occlusively. Using such optimised carriers, so-called Transfersomes, ensures reproducible and efficient transcutaneous carrier and drug transport. Insulin-loaded Transfersomes, for example, can deliver the drug through the non-compromised skin barrier with a reproducible drug effect that resembles closely that of an ultralente insulin injected under the skin; the pharmacokinetic and pharmacodynamic properties of the injected and transdermal insulin are also comparable. The efficacy of transcutaneously delivered insulin in Transfersomes is not affected by the previous therapy, similar results having been measured in patients normally receiving intensified insulin therapy or a continuous subcutaneous infusion of insulin solution. Systemic normoglycaemia that lasts at least 16 hours has been achieved using a single non-invasive, epicutaneous administration of insulin in Transfersomes. Experience with other drugs suggests that the biodistribution of injected and transcutaneously delivered drugs can be very similar. This notwithstanding, Transfersomes can be designed and applied so as to mediate site-specific drug delivery into peripheral musculoskeletal tissues or into the skin, as may be desired.