Formulation and biological distribution of radiolabeled 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea in an animal tumor model.

A formulation of 1-[2-chloroethyl-U-14C]-3-cyclohexyl-1-nitrosourea in ethanol:propylene glycol (1:4, v/v) was administered to rats previously infiltrated with RT6 glioma tumors (astrocytic series); the organ and tumor tissue distribution was followed at 1, 4, 12, and 24 hr postinjection. From 0 to 1 hr, rapid blood disappearance of the 1-[2-chloroethyl-U-14C]-3-cyclohexyl-1-nitrosourea was observed with a concomitant increase in all organs except the lung, muscle, and brain. After 24 hr, only the blood, liver, and muscle contained < 1% of the dose. Throughout the study, the bladder, liver, small intestine and kidneys concentrated the highest percentages on a per-gram basis. The distribution of 1-[2-chloroethyl-U-14C]-3-cyclohexyl-1-nitrosourea in the tumor relative to brain, blood, and muscle showed a maximum 4 to 12 hr after administration.