(–)-2β-Carboisopropoxy-3β-(4-iodophenyl)tropane (RTI-4229-121, IPCIT) is a stimulant drug used in scientific research, which was developed in the early 1990s.

[1] RTI-121 is a phenyltropane based, highly selective dopamine reuptake inhibitor[2] and is derived from methylecgonidine.

It is more selective for the dopamine transporter than other DAT radioligands such as β-CIT, and so has less nonspecific binding and produces "cleaner" images.

[5][6] Various radiolabelled forms of RTI-121 (with different radioactive isotopes of iodine used depending on the application) are used in both humans and animals to map the distribution of dopamine transporters in the brain.

Some jurisdictions such as the United States, Australia, and New Zealand, however, might however consider RTI-121 to be a controlled substance analogue of cocaine on the grounds of its related chemical structure.