RENAL EXCRETION OF METAIODOBENZYLGUANIDINE AFTER THERAPEUTIC DOSES INCANCER-PATIENTS AND ITS RELATION TO DOSE AND CREATININE CLEARANCE

Iodine-131 radioiodinated meta-iodobenzylguanidine (I-131-MIBG) is use d for diagnostic scintigraphy and radionuclide therapy of neural crest -derived tumours. In higher doses (up to 80 mg), non-radioactive MIBG is now evaluated for palliation in carcinoid patients. After administr ation of therapeutic doses of I-131-MIBG (3.7-7.4 GBq, 1.7-5.8 mg MIBG ) to patients aged 2-73 years, 53 +/- 8.8%, 69 +/- 7.8% and 83 +/- 7.0 % of the dose was cumulatively excreted as MIBG in the urine after 24, 48 and 72 h, respectively. Within the MIBG dose range of 1.7-80.0 mg, a linear relationship was found between the excretion rate over the f irst 24 h (mg per 24 h) and the dose. In adults, the MIBG excretion ra te over the first 24 h (% of dose per 24 h) was shown to be only parti ally related to the glomerular filtration rate (GFR).