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 ionto-phoresis 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/cm 2 or application of current for 12 h (at 0.5 mA/cm 2 ) led to 80 and 20% degradation respectively. All the samples showed biological activity comparable to intact insulin.