Vesicular systems for delivering conventional small organic molecules and larger macromolecules to and through human skin.

The history of using vesicular systems for drug delivery to and through skin started nearly three decades ago with a study utilising phospholipid liposomes to improve skin deposition and reduce systemic effects of triamcinolone acetonide. Subsequently, many researchers evaluated liposomes with respect to skin delivery, with the majority of them recording localised effects and relatively few studies showing transdermal delivery effects. Shortly after this, transfersomes were developed with claims about their ability to deliver their payload into and through the skin with efficiencies similar to subcutaneous administration. Since these vesicles are ultradeformable, they were thought to penetrate intact skin deep enough to reach the systemic circulation. Their mechanisms of action remain controversial, with diverse processes being reported. Parallel to this development, other classes of vesicles were produced, with ethanol being included into the vesicles to provide flexibility (as in ethosomes); vesicles were constructed from surfactants and cholesterol (as in niosomes). The ultradeformable vesicles showed variable efficiency in delivering low-molecular-weight and macromolecular drugs. This article will critically evaluate vesicular systems for dermal and transdermal delivery of drugs, considering both their efficacy and their potential mechanisms of action.