Enhanced delivery of drugs into and across the skin by ethosomal carriers

In dermal and transdermal delivery, the skin is used as a portal of entry for drugs, for localized and systemic treatment. Because of the barrier properties of the outer layer of the skin, in many cases, permeation-enhancing agents are needed to achieve therapeutic levels of drug. Classic liposomal systems were found to be effective at forming drug reservoir in the upper layers of the skin, for local skin therapy. Recently, it was found that ethosomal carriers, phospholipid vesicular systems containing relatively high concentrations of alcohol, were very effective at enhancing dermal and transdermal delivery of both lipophilic and hydrophilic molecules. Fluorescent probes delivered from ethosomal systems reached the deep strata of the skin. Delivery of minoxidil to the pilosebaceous units from ethosomes was much greater compared to delivery from classic liposomes. In addition, clinical studies with aciclovir showed that ethosomal formulations were superior to the currently available topical therapy at treating recurrent herpes labialis. Ethosomal systems were also highly effective at transdermal delivery of drugs. In vivo skin permeation of testosterone from patches containing ethosomal drug were more effective at delivering testosterone through rabbit pinna skin than commercially available Testoderm patches. Results using trihexyphenidyl hydrochloride ethosomes indicated that this system has the potential to be further developed into an antiparkinsonian patch. Lastly, the transdermal delivery of insulin from an ethosomal carrier resulted in lower blood glucose levels in normal and diabetic rats in vivo, with a plateau effect lasting for at least 8 h. (C) 2000 Wiley-Liss, Inc.