In view of the widespread application of methylphenidate for attention-deficit/hyperactivity
            disorder (ADHD) therapy its interaction with alcohol was investigated in an in-vitro assay and in a study involving 9 male volunteers. The study conditions were: methylphenidate
            (20 mg) only, ethylphenidate followed by ethanol (0.8 g/kg body weight) and ethanol
            followed by methylphenidate. Methylphenidate (CAS 113-45-1), ritalinic acid (CAS 19395-41-6)
            and ethylphenidate (CAS 57413-43-1) were assayed in blood samples collected up to
            7 h after ingestion using liquid chromatography-mass spectrometry (LC/MS). It was
            found that methylphenidate is hydrolyzed to ritalinic acid by the same esterase that
            de grades cocaine. In the presence of ethanol this is inhibited and the active metabolite
            ethylphenidate is formed. The pharmacokinetic evaluation showed that methyl-phenidate
            concentrations were not markedly affected by ethanol, but ritalinic acid concentrations
            were lower, especially if ethanol was ingested first Ethylphenidate concentrations
            were low with only about 10% of methylphenidate concentrations suggesting that concurrent
            ethanol use does not impair methylphenidate’s therapeutic efficacy. Unexpectedly one
            subject exhibited amethylphenidate hydrolysis defect yielding very high methylphenidate
            and lowritalinic acid concentrations in all studyconditions.
         Key words
CAS 113-45-1 - Ethanol, drug interaction - Genetic polymorphisms - Liquid chromatography-massspectrometry
            - Methylphenidate, drug interaction, metabolite kinetics