Modulation of gel formation and drug-release characteristics of lidocaine-loaded poly(vinyl alcohol)-tetraborate hydrogel systems using scavenger polyol sugars

Polyol sugars, displaying a plurality of hydroxyl groups, were shown to modulate tetrahydroxyborate (borate) cross-linking in lidocaine hydrochloride containing poly(vinyl alcohol) semi-solid hydrogels. Without polyol, demixing of borate cross-linked PVA hydrogels into two distinct phases was noticeable upon lidocaine hydrochloride addition, preventing further use as a topical system. d-Mannitol incorporation was found to be particularly suitable in circumventing network constriction induced by ionic and pH effects upon adding the hydrochloride salt of lidocaine. A test formulation (4% w/v lidocaine HCl, 2% w/v d-mannitol, 10% w/v PVA and 2.5% w/v THB) was shown to constitute an effective delivery system, which was characterised by an initial burst release and a drug release mechanism dependent on temperature, changing from a diffusion-controlled system to one with the properties of a reservoir system. The novel flow properties and innocuous adhesion of PVA–tetrahydroxyborate hydrogels support their application for drug delivery to exposed epithelial surfaces, such as lacerated wounds. Furthermore, addition of a polyol, such as d-mannitol, allows incorporation of soluble salt forms of active therapeutic agents by modulation of cross-linking density.