1995 Volume 10 Issue 6 Pages 819-829
The tissue distribution and excretion of 125I-iodixanol have been studied in the rat following single intravenous administration of 600 mg/kg.
Following single intravenous dose of 125I-iodixanol, the mean Cmax concentration of radioactivity in plasma was measured at 5 min, during the first sampling, and was 1079 μg equiv. I/ml. Mean concentrations then declined rapidly to 97.3 μg equiv. I/ml at 1 hr and to 14.3 μg equiv. I/ml at 2 hrs; at later times, concentrations were below the limit of accurate determination. There was no notable specific uptake of radioactivity into blood cells.
Following intravenous dosing, the radioactivity was rapidly and mainly excreted in the urine. During 72 hrs after dosing, the urinary excretion accounted in average for 88.3% of the dose and fecal excretion accounted for 5.9% of the dose. The total recovery of radioactivity during 72 hrs was 95.3% of the administered dose.
The highest levels of radioactivity occured at 0.5 hr and 1 hr in most tissues. At 0.5 hr, the following concentrations (expressed as μg equiv. I/g or ml) were found in kidneys (672), plasma (331), aorta (295), vena cava (246), thyroid (223) and whole-blood (202). After 2 hrs, concentrations generally declined, and by 72 hrs concentrations were near to, or below, the limit of accurate measurement, in most tissues. At 72 hrs, notable concentrations were only detected in the thyroid and kidney.
The extent of plasma protein binding of radioactivity was minimal and ranged between 1 % and 10% of the plasma radioactivity during 2 hrs after dosing.
In conclusion, this study has shown that after intravenous administration of 125I-iodixanol to rats, the drug is rapidly and generally distributed in the tissues. Radioacivity is generally rapidly cleared from most tissues and from plasma and is very rapidly excreted, almost exclusively in the urine.
