PHARMACOKINETICS OF RADIOPHARMACEUTICALS

The pharmacokinetics of various radiopharmaceuticals following i.v. ad ministration in mice and rats has been studied and compared. Before in jection the radiochemical purity (RP) of the compounds were determined by HPLC and PAGE. In all cases RP-s were higher than 90%. ne biodistr ibution of 99mTc labelled anti CEA IgG was studied in mice bearing hum an colon carcinoma xenografts. Animals with different tumour weights s howed different blood kinetic and tumor uptake. The pilot clinical stu dy of the 99mTc labelled anti melanoma Fab and 111-In-DTPA labelled an ti melanoma F(ab')2 showed differences in the pharmacokinetic paramete rs. (99mTc labelled: comp.A. 84.6%; T1/2:0.6 h, 111-In-labelled: comp. A.:46%, T1/2 1.5 h.) The various isonitril derivatives synthetized in our laboratory were labelled with 99mTc and the biodistribution were t ested in rats. The kinetic study showed that all the three molecules h ave different half lifes in the heart and liver (T1/2 for heart ranged 5.1-18.6 h, for liver T1/2:1.2-2.5 h). Reversed phase HPLC study of t he collected bile showed the 15-100% of injected compounds are metabol ized during hepatic excretion. Literature date and our recent observat ions confirm that the knowledge of pharmacokinetics of radiolabelled c ompounds both in research, development and clinical practice is of bas ic importance.