THE UPTAKE AND RELEASE OF MOLECULAR-IODINE BY THE SKIN - CHEMICAL ANDBACTERICIDAL EVIDENCE OF RESIDUAL EFFECTS CAUSED BY POVIDONE-IODINE PREPARATIONS

The residual effect of iodine-based disinfectants is caused by a dynam ic back-diffusion which is the reverse of the absorption occurring dur ing application. A very sensitive photometric method was used to measu re the iodine flux of the back-diffusion after treating the skin with povidone-iodine preparations and Lugol's solution. After removal of th e preparation the intensity of the iodine flux decreases with time and correlates with the amount of iodine being resorbed. The latter depen ds on the concentration of free molecular iodine of the preparation, t he contact time and the thickness of the horny layer of the treated sk in. With Lugol's solution (approximately 170 ppm free molecular iodine ) iodine flux could be observed 12-24 h after an application of 20-60 s, while with low-level povidone-iodine preparations (0.5-20 ppm free iodine) the measurable flux lasted only 0.5-1 h after an application t ime of 3 min. The bactericidal activity of the back-diffusing iodine f rom skin previously treated with a commercial povidone-iodine preparat ion was assayed by using an inoculation with Micrococcus luteus. This showed a logarithmic reduction of 0.4 in bacterial concentration. Sinc e the skin was washed with soap for 1 min after application this bacte ricidal action reflected the residual effect of the back-diffusing iod ine.