Biodistribution and excretion of 125I ioversol in conscious dogs

Radiolabeled ioversol was injected intravenously into two male and two female beagle dogs (6.7 to 10.4 kg) at two dose levels each (0.2 and 1.0 g I/kg). Blood levels of radioactivity were monitored at 2, 5, 10, 20, 40, 60, 90, and 120 minutes and at one and two days. Urine and feces were collected in metabolism cages for two days, at the end of which the dogs were killed and organs or tissues (kidneys, liver, spleen, lungs, thyroid glands, heart, gonads, and muscle) were sampled. Radioactivity in tissues and excreta was assayed. Biexponential disappearance of radioactivity from blood was observed in three of four dogs at each dose level. Distribution half-lives averaged 2.5 to 3.5 minutes. Elimination half-lives averaged 51 to 54 minutes. Volumes of distribution averaged 25% to 27% of body weight. No organ retention was evident at 48 hours. Recovery of ioversol in urine and feces averaged 86% to 88% of the administered dose, of which all but a few percent was recovered in urine. On chromatographic assay, ioversol accounted for an average of 103% to 109% of radioiodine, suggesting, within the experimental limits of the assay, that ioversol is excreted unchanged. No dose-related differences were evident in any of these measures. The pharmacokinetics and biodistribution of ioversol are consistent with those of other extracellularly distributed iodinated contrast agents that are excreted by the kidney.