Hyaluronan: Investigations into the mode of action of hyaluronan in topical drug delivery

Hyaluronan (HA) is a polyanionic, polysaccharide ubiquitous in mammals where it has a protective, structure stabilising and shock-absorbing role. The unique viscoelastic nature of HA along with its biocompatibility and non-immunogenicity has led to its use in a number of clinical applications. The ability of HA to localise therapeutic agents in the superficial layers of the skin has led to the commericalisation of Solaraze®, a 3% diclofenac in 2.5% HA gel, for the topical treatment of actinic keratoses (AKs), the third most common skin complaint in the US. However, the means by which HA enhances topical drug delivery remains unclear. The data described in this study demonstrate that HA offers promotes the delivery and localisation of drugs in the skin. In addition, it would appear that the molecular weight and concentration of HA may be critical for such drug delivery properties.