Relationship between Development of Diarrhea and the Concentration of SN‐38, an Active Metabolite of CPT‐11, in the Intestine and the Blood Plasma of Athymic Mice Following Intraperitoneal Administration of CPT‐11

Severe diarrhea occurred during daily intraperitoneal administration of 7‐ethyl‐10‐[4‐(l‐piperidino)‐l‐piperidino]carbonyloxycamptothecin (CPT‐11) at a dose of 50 mg/kg in athymic mouse. Serial determination of CPT‐11 and 7‐ethyl‐10‐hydroxycamptothecin (SN‐38), with the use of an on‐line solid extraction HPLC system, demonstrated that much higher levels of the compounds are retained in the intestine and the blood plasma after five consecutive daily injections than after a single injection. Histologic examination of the gastrointestinal tract showed hemorrhagic colitis on day 7 and later after five consecutive daily injections of CPT‐11. The direct cause of diarrhea associated with CPT‐11 administration is considered to be enterocolitis caused by high levels of SN‐38 and/or CPT‐11 retained for a long period in the intestine.