ADAM I-123 is a radiopharmaceutical containing the serotonin transporter (SERT) ligand ADAM [2-((2-((dimethylamino)methyl)phenyl)thio)-5-iodophenylamine] labeled with the radioisotope iodine I 123, with SERT-binding and radioisotope activities. Upon administration, iodine I 123 ADAM selectively binds to SERT-expressing cells; subsequently, SERT-expressing tissues may be visualized using single photon emission computed tomography (SPECT). SERT is a monamine transporter protein found in the membranes of neurons and platelets; in neurons it transports the neurotransmitter serotonin from synaptic spaces into presynaptic neurons, terminating serotonin's function.