RTI(-4229)-55, also calledRTI-55 oriometopane, is aphenyltropane-basedpsychostimulant used in scientific research and in some medical applications. This drug was first cited in 1991.[1] RTI-55 is a non-selectivedopamine reuptake inhibitor derived frommethylecgonidine. However, more selective analogs are derived by conversion to "pyrrolidinoamido"RTI-229, for instance. Due to the large bulbous nature of the weakly electron withdrawing iodo halogen atom, RTI-55 is the most strongly serotonergic of the simplepara-substitutedtroparil based analogs.[2] In rodents RTI-55 actually caused death at a dosage of 100 mg/kg, whereas RTI-51 and RTI-31 did not.[2] Another notable observation is the strong propensity of RTI-55 to causelocomotor activity enhancements,[2] although in an earlier study, RTI-51 was actually even stronger than RTI-55 in shifting baseline LMA.[3] This observation serves to highlight the disparities that can arise between studies.
RTI-55 is one of the most potent phenyltropane stimulants commercially available, which limits its use in humans, as it might have significant abuse potential if used outside a strictly controlled medical setting.[4] However, it is definitely worthy of mentioning that increasing the size of the halogen atom attached to troparil serves to reduce the number of lever responses in a session when these analogs were compared in a study.[5] Although RTI-55 wasn't specifically examined in this study the number of lever responses in a given session was of the order cocaine > WIN35428 > RTI-31 > RTI-51.
In contrast toRTI-31 which is predominantly dopaminergic, increasing the size of the covalently bonded halogen from a chlorine to an iodine markedly increases the affinity for theSERT, while retaining mostly all of itsDAT blocking activity.
RTI-55 is mainly used in scientific research into thedopamine reuptake transporter. Variousradiolabelled forms of RTI-55 (with different radioactiveisotopes ofiodine used depending on the application) are used in both humans and animals to map the distribution ofdopamine transporters andserotonin transporters in thebrain.[6][7] The123I derivative is known as iometopane.
^Shaya EK, Scheffel U, Dannals RF, Ricaurte GA, Carroll FI, Wagner HN, et al. (February 1992). "In vivo imaging of dopamine reuptake sites in the primate brain using single photon emission computed tomography (SPECT) and iodine-123 labeled RTI-55".Synapse.10 (2):169–72.doi:10.1002/syn.890100210.PMID1585258.S2CID38478862.
^Shang Y, Gibbs MA, Marek GJ, Stiger T, Burstein AH, Marek K, et al. (February 2007). "Displacement of serotonin and dopamine transporters by venlafaxine extended release capsule at steady state: a [123I]2beta-carbomethoxy-3beta-(4-iodophenyl)-tropane single photon emission computed tomography imaging study".Journal of Clinical Psychopharmacology.27 (1):71–5.doi:10.1097/JCP.0b013e31802e0017.PMID17224717.S2CID25239273.
^Staffen W, Mair A, Unterrainer J, Trinka E, Bsteh C, Ladurner G (May 2000). "[123I] beta-CIT binding and SPET compared with clinical diagnosis in parkinsonism".Nuclear Medicine Communications.21 (5):417–24.doi:10.1097/00006231-200005000-00002.PMID10874697.
