Radiochemical stability during infusion of 131I-labelled metaiodobenzylguanidine for therapeutic use.

131I-labelled metaiodobenzylguanidine ([131I]MIBG) is used both for diagnostic scintigraphy and for radionuclide therapy of neural crest derived tumours in particular neuroblastoma, malignant phaeochromocytoma and paraganglioma. This paper presents data on radiochemical stability during the infusion of 3.8, 5.7 and 7.7 GBq [131I]MIBG in 100 ml infusion fluids for therapy. The period of investigation started at the moment of dilution of the thawed infusion concentrates (t = 0), which arrived in a frozen condition from the manufacturer, and ended at the termination of infusion (t = 7 h). In 7 h the percentage of free [131I]iodide increased from 3.74 to 5.82, from 3.52 to 6.02 and from 3.72 to 6.40% in the 3.8, 5.7 and 7.7 GBq [131I]MIBG infusion fluids, respectively. The 0-7 h increases of the different radioactive concentrations did not differ significantly. All the infusion fluids contained less than 7% free [131I]iodide at the end of infusion (t = 7 h).