Treatment of pain disorders with (1R,4S)-trans 4-(3,4-dichlorophenyl)-1,2,3,4-tetrahydro-1-napthalenamine; and (1S,4R)-trans 4-(3,4-dichlorophenyl)-1,2,3,4-tetrahydro-1-napthalenamine is disclosed. A process for preparing 4-(3,4-dichlorophenyl)-1,2,3,4-tetrahydro-1-napthalenamine is also disclosed. The process includes the preparation of all four isomers of N-[4-(3,4-dichlorophenyl)-1,2,3,4-tetrahydronaphthalen-1-yl]formamide, which are also useful in treatment of pain disorders.