Intraperitoneal povidone-iodine in experimental canine and murine peritonitis

In dogs with appendicitis-peritonitis, intraperitoneal povidone-iodine caused death more rapidly than the instillation of saline solution. The bacterial content of canine peritoneal fluid increased with time. Although fewer bacteria were found in fluid from povidone-iodine-treated dogs, the differences were not statistically significant. Qualitative chemical analysis of peritoneal fluid revealed iodide, but not free iodine, 15 to 30 minutes after instillation of povidone-iodine. Iodine was present in the peritoneum at 2 hours but not at 3 or 6 hours. The antibacterial effect of povidone-iodine was demonstrated in mice challenged intraperitoneally with lethal doses of Escherichia coli. Povidone-iodine diminished mortality when injected immediately (p less than 0.005) but not when given 1 to 3 hours later. Immediate injection of povidone-iodine into mice lowered the number of E. coli by 3 logs. Injection of povidone-iodine 3 hours after bacterial challenge lowered the number of E. coli by only 1/3 log. This lesser bactericidal effect in mice is attributed to greater dispersal and sequestration of bacteria throughout the peritoneal cavity with time and with inactivation of povidone-iodine by reduction to iodide in vivo. In dogs with appendicitis-peritonitis, the more rapid death after treatment with povidone-iodine was not associated with differences in peritoneal microflora but with peritoneal absorption of excessive amounts of iodide.