Metabolism of I-131-meta-iodobenzylguanidine (MIBG) in humans

Conference · Sun Jan 01 04:00:00 EST 1984 · J. Nucl. Med.; (United States)

OSTI ID:6606087

Mangner, T J; Tobes, M C; Wieland, D M; Sisson, J C

I-131-MIBG is used to image and treat human pheochrmocytoma. As part of a pharmacodynamic study, the authors have evaluated its excretion and metabolism in 8 pheochromocytoma patients undergoing MIBG therapy. Following diagnostic doses (0.42-0.53 mCi) of I-131-MIBG given prior to therapy, 40-55% of the administered radioactivity appears in the urine within 24 h with 70-90% recoverable within 4 days. HPLC was used to identify potential metabolites following therapeutic doses (130-213 mCi) of I-131-NIBG. Aliquots of daily urine samples were prepared for HPLC analysis by passage through C-18 Sep-pak cartridges. A reverse-phase HPLC system (..mu..Bondapak C-18; 0.2 M ammonium phosphate/THF, 80/20) with both ultraviolet (254 nm) and radioactive (Flo-one detector, solid scintillant cell) detection was used. Radioactive metabolites were identified by co-chromatography with authentic compounds at elution solvent pH's of 4.6 and 7.0. Unaltered I-131-MIBG was the primary radioactive urinary component in all 8 patients studied, representing 74-90% of the total recovered. Two ''major'' metabolites were identified: I-131-iodide and I-131-m-iodohippuric acid, representing, respectively, 2-6% and 2-16% of the total urinary radioactivity. Of 4 additional ''minor'' metabolites (< 2% of total urinary radioactivity) detected, 2 have been identified: I-131-4-hydroxy-MIBG and I-131-m-iodobenzoic acid. The 4-5 day metabolism profiles varied from patient to patient but did not change in 2 patients given 2 therapy doses 4 months apart. No obvious correlation was observed between the presence of metabolites and the location of the tumors or the plasma or urinary catecholamine levels. I-131-MIBC is a rapidly excreted, relatively stable radiopharmaceutical agent.

• Research Organization: Univ. of Michigan Medical Center, Ann Arbor, MI
• OSTI ID: 6606087
• Report Number(s): CONF-840619-
• Conference Information: Journal Name: J. Nucl. Med.; (United States) Journal Volume: 25:5
• Country of Publication: United States
• Language: English

Related Subjects

550501* -- Metabolism-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
AUTONOMIC NERVOUS SYSTEM
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BIOLOGICAL MATERIALS
BIOLOGICAL VARIABILITY
BIOLOGICAL WASTES
BODY FLUIDS
CHROMATOGRAPHY
CLEARANCE
DAYS LIVING RADIOISOTOPES
DIAGNOSIS
DISEASES
DRUGS
EXCRETION
INTERMEDIATE MASS NUCLEI
IODINE 131
IODINE ISOTOPES
ISOTOPES
LABELLED COMPOUNDS
LIQUID COLUMN CHROMATOGRAPHY
MATERIALS
METABOLISM
METABOLITES
MIBG
NEOPLASMS
NERVOUS SYSTEM
NUCLEI
ODD-EVEN NUCLEI
PATIENTS
RADIOISOTOPES
RADIOPHARMACEUTICALS
SEPARATION PROCESSES
SPECTRA
ULTRAVIOLET SPECTRA
URINE
WASTES