Stability of insulin under iontophoretic conditions.

The present study focuses on the physical and chemical stability of insulin under iontophoretic conditions using HPLC, SDS-PAGE, RIA and biological assay. Influence of pH, concentration of insulin, current strength and duration of current application on the stability of insulin was studied. Anodal iontophoresis at pH 7.4 caused more than 80% degradation of insulin, while the degradation was minimal at pH 3.6. The degradation was not influenced by insulin concentration, but increase in current strength above 0.75 mA/cm2 or application of current for 12 h (at 0.5 mA/cm2) led to 80 and 20% degradation respectively. All the samples showed biological activity comparable to intact insulin.