Critical evaluation of cadexomer-iodine ointment and povidone-iodine sugar ointment

Topical iodine forms are used for infected and necrotic pressure ulcers. Despite antimicrobial advantages several potential disadvantages were observed with controversial results. To clarify the controversy, the reactivity of povidone-iodine (PI) sugar ointment and cadexomer-iodine (CI) ointment toward biological components was investigated. l-Tyrosine as a component of proteins and egg lecithin as a component of lipid membranes were reacted with forms of iodine. Furthermore, water absorption abilities of ointments were investigated. The reactions of PI sugar ointment and CI ointment with l-tyrosine were reversely dependent on iodine concentrations. CI ointment reacted with lecithin in an iodine concentration dependent manner, while PI sugar ointment reacted with lecithin in an iodine concentration independent steady manner. However, at the clinically relevant iodine concentration (0.1, w/v%) PI sugar ointment reacted efficiently with l-tyrosine and less efficiently with lecithin, while CI ointment reacted efficiently with lecithin and less efficiently with l-tyrosine. Water absorption rate constant was 29.9 mg/cm2/min0.5 for PI sugar ointment and 15.3 for CI ointment. Water absorption capacity per weight over 24 h was 76% for PI sugar ointment and 26% for CI ointment. These results suggest that PI sugar ointment and CI ointment have different characteristics for iodine reactivity and water absorption.