PVA Cryogel as model hydrogel for iontophoretic transdermal drug delivery investigations. Comparison with PAA/PVA and PAA/PVP interpenetrating networks

The use of polyvinyl alcohol (PVA)cryogel as a model hydrogel for iontophoretic transdermal investigations is proposed. Due to the excellent combination of its properties, it could be used for evaluating iontophoretic transdermal delivery of variety of drugs, regardless of pK_a, pH or presence of auxiliary ions. Applicability of PVA Cryogel for drug delivery purposes was compared to those of polyacrylic acid/polyvinyl alcohol (PAA/PVA)and polyacrylic acid/polyvinylpyrrolidone (PAA/PVP)adhesive interpenetrating networks. Swelling properties of PVA Cryogel were shown to be almost independent on pH and NaCl concentration, while swelling of PAA-based gels was significantly affected. Addition of PVA and PVP to PAA decreased swelling degrees and increased adhesivity and compression moduli. Iontophoretic experiments were performed using a donor gel/skin/receptor gel configuration; current density and delivery duration were varied. Dexamethasone sodium phosphate was used as model drug molecule. PVA Cryogel was used for investigating the influence of NaCl concentration, which can alter the amount of current carried by the drug ions and, therefore, the delivery rate. By using PVA Cryogel it was possible to easily determine the amount of drug permeated through the skin into the receptor gel, the amount retained by the skin and the amount remained in the donor hydrogel. Decreasing NaCl concentration in PVA Cryogel resulted in higher total amounts of drug delivered and significantly enhanced drug permeation through the lower layers of the skin into the receptor hydrogel.