It is complicated to explain which isomers are desired. For example, although Alan P. Kozikowski showed that "R/S" nocaine is less addictive than "SS" Nocaine, studies on variously substituted phenyltropanes by F. Ivy Carroll "et at." revealed that the ββ isomers were less likely to cause convulsions, tremor and death than the corresponding "trans" isomers (more specifically, what is meant is the 1"R",2"R",3"S" isomers). While it does still have to be conceded that RTI-55 caused death at a dosage of 100 mg/kg, it's therapeutic index of safety is still much better than the corresponding "trans" isomers because it is more potent compound.