Attention deficit hyperactivity disorder management
There are two major medications derived from methylphenidate's isomers: a racemic mixture of half d-threo-methylphenidate and half l-threo-methylphenidate called methylphenidate (Ritalin, Concerta), and an enantiopure formulation containing just d-threo-methylphenidate called dexmethylphenidate (Focalin).
Nortilidine
Nortilidine is the major active metabolite of tilidine. It is formed from tilidine by demethylation in the liver. The racemate has opioid analgesic effects roughly equivalent in potency to that of morphine but virtually all of the opioid activity resides in the (1S,2R) isomer. The (1R,2S) isomer has NMDA antagonist activity. The drug also acts as a dopamine reuptake inhibitor. The reversed-ester of nortilidine is also known which has almost identical properties to nortilidine.