Microneedle-mediated Drug Delivery

This chapter aims to review some of the work performed on the transdermal delivery of low and high molecular weight compounds using various microneedle (MN) systems. It describes the mechanisms of MN systems. The chapter demonstrates that addition of hyaluronidase, an enzyme that breaks down hyaluronic acid within skin collagen fibres, to the infusion liquid increased flow rate sevenfold. Pre-treatment of the skin with a solid MN array, followed by application of a drug formulation for diffusion through the resulting skin pores, was the first reported strategy for MN use. Coated MNs, which have the drug adhered on to the surface of the needles, offer a more controlled and potentially efficient route of transdermal drug delivery than that described for skin pre-treatment with solid MNs. Hydrogel microparticles were incorporated into biodegradable PLGA MNs, in an attempt to achieve sustained delivery of both hydrophobic and hydrophilic drugs.