Radiopharmacological studies of 125I-labeled ifosfamide in rats

Abstract Isophosphamide, which is a phosphoramid mustard analogous to cyclophosphamide was labeled by isotopic exchange with radioactive iodines. The pharmacokinetic studies in normal rats showed a bicompartmental model with a 7 h mean of the total half-life for the second slope. 70% of the total activity is found in the urine after 48 h and is mainly non-metabolized isophosphamide. The uptake in tissues of tumorous mice (Sarcoma IA) demonstrated an accumulation of activity in liver (normal place of microsomal metabolism), in kidneys and in tumor tissue. The uptake index in the tumor is favorable but the iodide release and further accumulation of it in the thyroid and the digestive tract is an empediment for human exploration.