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).
Ritalinic acid
Ritalinic acid is a substituted phenethylamine and an inactive major metabolite of the psychostimulant drugs methylphenidate and ethylphenidate. When administered orally, methylphenidate is extensively metabolized in the liver by hydrolysis of the ester group yielding ritalinic acid. The hydrolysis was found to be catalyzed by carboxylesterase 1 (CES1).
Ritalinic acid is used as an intermediate in the synthesis of methylphenidate and its analogues, such as ethylphenidate and isopropylphenidate.