RTI-51
-2β-Carbomethoxy-3β-tropane is a semi-synthetic alkaloid in the phenyltropane group of psychostimulant compounds. First publicized in the 1990s, it has not been used enough to have gained a fully established profile. RTI-51 can be expected to have properties lying somewhere in between RTI-31 and RTI-55. It has a ratio of monoamine reuptake inhibition of dopamine > serotonin > norepinephrine which is an unusual balance of effects not produced by other commonly used compounds. It has been used in its radiolabelled form to map the distribution of dopamine transporters in the brain.
Modern research seems to confirm the above hypothesis. However, earlier work produced more scattered results. Based upon what is obvious from the table, RTI-31, RTI-51, and RTI-55 are all similarly potent TRIs.
| Compound | CFT | DA | Nisoxetine | NE | Paroxetine | 5-HT |
| Cocaine | 89.1 | 275 cf. 241 | 3300 | 119 cf. 161 | 1050 | 177 cf. 112 |
| WIN 35,065-2 | 23 | 49.8 | 920 | 37.2 | 1960 | 173 |
| WIN 35,428 | 13.9 | 23.0 | 835 | 38.6 | 692 | 101 |
| RTI-31 | 1.1 | 3.68 | 37 | 5.86 | 44.5 | 5.00 |
| RTI-113 | 1.98 | 5.25 | 2,926 | 242 | 2,340 | 391 |
| RTI-51 | 1.7 | ? | 37.4 | ? | 10.6 | ? |
| RTI-55 | 1.3 | 1.96 | 36 | 7.51 | 4.21 | 1.74 |
| RTI-32 | 1.7 | 7.02 | 60 | 8.42 | 240 | 19.4 |
Data in above table is from rats brains. More recent work has advocated using cloned human transporters.