In vitro Passive and Iontophoretically Assisted Transport of Salbutamol sulphate through Hairless Mice Skin

Abstract

Investigations were carried out to ascertain the relative importance of the described mechanism in iontophoretic transport using an ionizable drug salbutamol sulphate, which has two pKa values 9.3 (for amino group) and 10.3 (for phenolic group). Ionization of salbutamol sulphate varies with pH, hence the rate and extent of transport across the skin can be enhanced, controlled and manipulated by the application of factors like anodal and cathodal current at varied pH of donor solution and current densities. To determine these parameters, experiments were performed and data was collected at 7.4, 9.3, 10.3 and 11 pH using 4mg/ml drug concentration and 0.3mA/cm2 current density for 6 hours. After establishing the pH for optimum transport of drug, effect of current density (0.1, 0.2, 0.3 and 0.4 mA/cm2) on the transport of drug (keeping drug concentration constant) were investigated. Passive diffusion of salbutamol sulphate was maximal at pH 10.3 and 9.3, when unionized form of drug was 50%. Anodal iontophoresis at pH 7.4 was most effective (significant result,                p < 0.05) in transport of drug across skin as compared to cathodal iontophoresis at pH 11. The effect of current density on steady state flux by salbutamol sulphate during anodal iontophoresis at 7.4 pH showed 2.26 and 28.05µg/cm2/h at 0.0 i.e., passive diffusion and 0.4 mA/cm2, respectively. Thus, flux was enhanced nearly 12 times during anodal iontophoresis.