RTI(-4229)-55, also called RTI-55 or iometopane, is a phenyltropane-based psychostimulant used in scientific research and in some medical applications. This drug was first cited in 1991. RTI-55 is a non-selective dopamine reuptake inhibitor derived from methylecgonidine. 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 simple para-substituted troparil based analogs. In rodents RTI-55 actually caused death at a dosage of 100 mg/kg, whereas RTI-51 and RTI-31 did not. Another notable observation is the strong propensity of RTI-55 to cause locomotor activity enhancements, although in an earlier study, RTI-51 was actually even stronger than RTI-55 in shifting baseline LMA. 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. 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. 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 to RTI-31 which is predominantly dopaminergic, increasing the size of the covalently bonded halogen from a chlorine to an iodine markedly increases the affinity for the SERT, while retaining mostly all of its DAT blocking activity.
^ abcCarroll, F. I.; Runyon, S. P.; Abraham, P.; Navarro, H.; Kuhar, M. J.; Pollard, G. T.; Howard, J. L. (2004). "Monoamine Transporter Binding, Locomotor Activity, and Drug Discrimination Properties of 3-(4-Substituted-phenyl)tropane-2-carboxylic Acid Methyl Ester Isomers". Journal of Medicinal Chemistry. 47 (25): 6401–6409. doi:10.1021/jm0401311. PMID15566309.
^Weed, M. R.; MacKevicius, A. S.; Kebabian, J.; Woolverton, W. L. (1995). "Reinforcing and discriminative stimulus effects of beta-CIT in rhesus monkeys". Pharmacology Biochemistry and Behavior. 51 (4): 953–956. doi:10.1016/0091-3057(95)00032-r. PMID7675883.
^Wee, S.; Carroll, F.; Woolverton, W. (2006). "A reduced rate of in vivo dopamine transporter binding is associated with lower relative reinforcing efficacy of stimulants". Neuropsychopharmacology. 31 (2): 351–362. doi:10.1038/sj.npp.1300795. PMID15957006.
^Shaya, E.; Scheffel, U.; Dannals, R.; Ricaurte, G.; Carroll, F.; Wagner Jr, J.; Kuhar, M.; Wong, D. (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): 169–172. doi:10.1002/syn.890100210. PMID1585258.
^Shang, Y.; Gibbs, M.; Marek, G.; Stiger, T.; Burstein, A.; Marek, K.; Seibyl, J.; Rogers, J. (2007). "Displacement of serotonin and dopamine transporters by venlafaxine extended release capsule at steady state: a 123I2beta-carbomethoxy-3beta-(4-iodophenyl)-tropane single photon emission computed tomography imaging study". Journal of Clinical Psychopharmacology. 27 (1): 71–75. doi:10.1097/JCP.0b013e31802e0017. PMID17224717.
^Staffen, W.; Mair, A.; Unterrainer, J.; Trinka, E.; Bsteh, C.; Ladurner, G. (2000). "123I beta-CIT binding and SPET compared with clinical diagnosis in parkinsonism". Nuclear medicine communications. 21 (5): 417–424. doi:10.1097/00006231-200005000-00002. PMID10874697.
^Zubal, I.; Early, M.; Yuan, O.; Jennings, D.; Marek, K.; Seibyl, J. (2007). "Optimized, automated striatal uptake analysis applied to SPECT brain scans of Parkinson's disease patients". Journal of Nuclear Medicine. 48 (6): 857–864. doi:10.2967/jnumed.106.037432. PMID17504864.
^Seppi, K.; Scherfler, C.; Donnemiller, E.; Virgolini, I.; Schocke, M. F. H.; Goebel, G.; Mair, K. J.; Boesch, S.; Brenneis, C.; Wenning, G. K.; Poewe, W. (2006). "Topography of dopamine transporter availability in progressive supranuclear palsy: a voxelwise 123Ibeta-CIT SPECT analysis". Archives of Neurology. 63 (8): 1154–1160. doi:10.1001/archneur.63.8.1154. PMID16908744.
^Musachio, J.; Keverline, K.; Carroll, F.; Dannals, R. (1996). "3 Beta-(p-trimethylsilylphenyl)tropane-2 beta-carboxylic acid methyl ester: a new precursor for the preparation of 123IRTI-55". Applied Radiation and Isotopes. 47 (1): 79–81. doi:10.1016/0969-8043(95)00259-6. PMID8589674.