A radiopharmaceutical containing the dopamine D2/D3 receptor agonist iodobenzamide (IBZM) labeled with the radionuclide iodine I 123 with dopamine receptor-binding and radioisotopic activities. Upon administration, iodine I 123 iodobenzamide binds to dopamine D2/D3 receptors; subsequently, tissues expressing these receptors can be visualized using single photon emission computed tomography (SPECT). Dopamine receptors are a class of metabotropic G protein-coupled receptors found in the central nervous system (CNS) and neuroendocrine tumors such as pheochromocytoma and paraganglioma.