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  • Title: Toxicokinetic assessment of methylphenidate (Ritalin) in a 13-week oral toxicity study in dogs.
    Author: Bakhtiar R, Ramos L, Tse FL.
    Journal: Biomed Chromatogr; 2004 Jan; 18(1):45-50. PubMed ID: 14872548.
    Abstract:
    Ritalin or methylphenidate (MPH) is often prescribed for the treatment of attention deficit hyperactivity disorder (ADHD) and narcolepsy. The therapeutic activity of MPH is principally due to D-threo-[2R,2'R]-MPH. Hence, in order to establish a kinetic relationship between doses and exposure levels in a non-rodent species, a 13-week oral (capsule) toxicity study of D-threo-[2R,2'R]-MPH was performed in beagle dogs. A previously reported chiral liquid chromatography tandem mass spectrometry (LC-MS/MS) with a limit of quantification (LLOQ) of 1.09 ng/ml was utilized. The results of this study indicated that MPH appeared to be rapidly absorbed in dogs following oral administration. The peak concentration was reached within 1-2 h. Based on the area under the curve (AUC) values, the plasma exposure of D-MPH was over-proportional to the dose. With the exception of two groups of animals (male/female, 7.5 mg/kg/day on day 1 and male/female, 3.0 mg/kg/day on week 7), the data showed no difference in MPH concentrations between the male and female dogs. Taking the statistical variations into account, concentrations of D-MPH that were observed after 7.5 mg/kg/day doses of D-MPH and 15 mg/kg/day doses of the racemate were similar. Following the racemate doses, the concentrations of L-MPH were consistently higher than those of the D-isomer. No accumulation of MPH was observed after 13 weeks of repeated daily administration.
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