Disposition of 14C-labelled FCE 22101 in animals.

14C-FCE 22101 was given intravenously to rats (4, 16 and 38 mg/kg), dogs (69 mg/kg), rabbits (99 mg/kg) and monkeys (41 and 99 mg/kg). Radioactivity was eliminated mainly in urine, with faecal excretion being less than 10% in all animal species. Radioactivity as expired 14CO2 was detected in the rat and accounted for less than 0.5% of the dose in 24 h. Tissue distribution was also investigated in the rat (38 mg/kg). After combustion and radioactivity counts the highest concentration of radioactivity was observed in the kidneys, followed by the lung, the skin and hair, and lastly by the liver and adrenals. Brain levels of radioactivity, corrected for blood contamination, were 40 to 60 times lower than the corresponding blood levels. The results of whole body autoradiography confirmed those above. Whole body autoradiography of pregnant rats did not show any transfer of radioactivity into fetuses and only low radioactivity was present in the placenta.