WHOLE-BODY QUANTITATIVE AUTORADIOGRAPHIC STUDY OF THE BIODISTRIBUTIONOF IOBITRIDOL IN RATS

RATIONALE AND OBJECTIVES. Iobitridol is a new nonionic low-osmolality contrast medium, During preclinical development of this agent, it was of interest to verify that it behaves like other urographic and angiog raphic contrast agents (i.e,, as a tracer of extracellular fluid). MET HODS. Male and female rats were imaged using a quantitative autoradiog raphic method after intravenous administration of iodine-125-labeled p roduct at a dose of 300 mg iodine/kg. RESULTS. The radioactivity was r apidly distributed with substantial uptake in the thyroid, kidneys, an d skin after 10 minutes, The central nervous system showed no uptake. The radioactivity was rapidly eliminated (i.e,, after 24 and 48 hours, only traces were found) except in the thyroid (because of free radiol abeled iodides present in small quantities in the administered solutio n). The considerable renal uptake after administration can be attribut ed to urinary excretion of the radioactivity (86% of the administered dose after 24 hours), Total elimination was achieved after 48 hours. N o sex-related effects were observed. CONCLUSION. The absence of a targ et organ, the abundant and rapid urinary elimination, and the absence of transfer across the blood-brain barrier suggest that iobitridol is a tracer of extracellular fluid.