IOBENGUANE I-123 (AdreView®) is a radiopharmaceutical agent for gamma-scintigraphy. It is similar in structure to the antihypertensive drug guanethidine and to the neurotransmitter norepinephrine (NE). IOBENGUANE is, therefore, largely subject to the same uptake and accumulation pathways as NE. It is taken up by the NE transporter in adrenergic nerve terminals and stored in the presynaptic storage vesicles. IOBENGUANE accumulates in adrenergically innervated tissues such as the adrenal medulla, salivary glands, heart, liver, spleen, and lungs as well as tumors derived from the neural crest. By labeling IOBENGUANE with the isotope iodine 123 (I-123), it is possible to obtain scintigraphic images of the organs and tissues in which the radiopharmaceutical accumulates. IOBENGUANE I-123 (AdreView®) is indicated for use in the detection of primary or metastatic pheochromocytoma or neuroblastoma. It is also used for scintigraphic assessment of sympathetic innervation of the myocardium by measurement of the heart to mediastinum (H/M) ratio of radioactivity uptake in patients with New York Heart Association (NYHA) class II or class III heart failure and left ventricular ejection fraction (LVEF) ≤ 35%. Among these patients, IOBENGUANE I-123 (AdreView®) may be used to help identify patients with lower one and two-year mortality risks, as indicated by an H/M ratio ≥ 1.6.