Administration in a hypotonic solution is preferable to dose escalation in intraperitoneal cisplatin chemotherapy for peritoneal carcinomatosis in rats.

An animal model of intraperitoneal (i.p.) cisplatin chemotherapy using hypotonic solutions of sodium chloride has been developed as a treatment for peritoneal carcinomatosis. The concentrations of platinum in the plasma and in the i.p. fluid of Donryu rats were measured after i.p. injection of hypotonic (103 or 154 mosm/l) and isotonic (308 mosm/l) solutions that contained an equal amount of cisplatin. The maximum concentration (Cmax) and the area under the curve of concentration versus time (AUC) of platinum in the plasma increased proportionately with increases in the dose of cisplatin and they were significantly higher in rats given cisplatin in hypotonic solutions than in those given the drug in isotonic solution. The Cmax and AUC of total platinum were similar for the solution of 103 mosm/l with 2.5 mg/kg cisplatin and the isotonic solution with 5.0 mg/kg cisplatin. The Cmax and AUC of free platinum in the plasma did not increase with increases in the dose of cisplatin in isotonic solution but did increase after hypotonic injection. However, the solutions of lower osmolarity gave a decreased AUC of platinum in the i.p. fluid. Hypotonic conditions continued for 30 min at most after i.p. injection of hypotonic solutions. When the same dose of cisplatin was given to rats with tumors derived from AH100B carcinoma cells, the amount of platinum taken by i.p. solid tumors from the solution of 103 mosm/l was about twice that from the isotonic solution and was much the same as that taken up from the isotonic solution with twice the amount of cisplatin. These results indicate that hypotonic i.p. cisplatin chemotherapy might be preferable to escalation of the dose of i.p. cisplatin in the treatment of peritoneal carcinomatosis.