Pharmacokinetics of intraperitoneal irinotecan in a pig model

Complete surgical cytoreduction of peritoneal implants and immediate intraperitoneal (lP) chemotherapy offers the greatest survival in selected patients with peritoneal carcinomatosis. This study was undertaken to describe the metabolism and pharmacokinetics of normothermic intraperitoneal CPT-11, free and glucuronized SN-38, in a pig model. Thirteen pigs were used for experimentation. Animals were grouped for IV and IP CPT-1 1 administration. Eleven pigs underwent laparotomy through a midline incision and instillation of 100, 200, and 400mg IP CPT-11. Systemic venous blood, portal blood and peritoneal fluid samples were taken at 5, 10, 20, 30, and 45 min, then every hour up to 8 hr for the 100 mg. For the three groups, peritoneal CPT-11 exposition was on average 4.9 times greater in the peritoneum than in the systemic venous or portal circulations and the systemic CPT-11 fraction absorbed from the peritoneum linearly increased with time. Free SN-38 was measurable in the earliest peritoneal samples taken. The initial instillation dose of CPT-11 did not impact on the SN-38 converted fraction, which remained stable at approximately 0.04% during the first 4 hour. Mean peritoneal SN-38: CPT-11 AUC ratio was 0.043. OPT-11 peritoneal conversion into SN-38 appeared slightly Inferior to the systemic conversion ratio. This norrnothermic IP OPT-11 pharmacokinetic study performed in a pig model confirms the possibility to achieve at least a 30 times higher peritoneal than systemic exposure. Peritoneal exposure to active SN-38 begins at the moment of CPT-11 peritoneal instillation. A fixed and small traction of less than 0.1% of CPT-11 is converted into SN-38, underlying the importance of a sufficient initial IP dose of CPT-11.