Pharmacokinetics of methylphenidate in hyperkinetic children

1 Pharmacokinetic study has been carried out following oral administration of 10-20 mg of methylphenidate hydrochloride to four behaviorally disorders children. 2 It is indicated that the drug is metabolized to ritalinic acid with an apparent plasma half life of 2.5 h. 3 The variability in magnitude of plasma concentration seems to be due not to its metabolism to ritalinic acid but due to the variability in the apparent volume of distribution. 4 The brief half life of methylphenidate which parallels the short duration of action of methylphenidate in behaviorally disordered children may be explained in part by its low protein binding which results in high percentage of free drug being made available for metabolism to pharmacologically inactive metabolites.