(–)-2β-Carboisopropoxy-3β-(4-iodophenyl)tropane (RTI-121, IPCIT) is a stimulant drug used in scientific research, which was developed in the early 1990s. RTI-121 is a phenyltropane based, highly selective dopamine reuptake inhibitor and is derived from methylecgonidine. RTI-121 is a potent and long-lasting stimulant, producing stimulant effects for more than 10 hours after a single dose in mice which would limit its potential uses in humans, as it might have significant abuse potential if used outside of a medical setting. However RTI-121 occupies the dopamine transporter more slowly than cocaine, and so might have lower abuse potential than cocaine itself.

RTI-121 is mainly used in scientific research into the dopamine reuptake transporter. 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. 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.