PHARMACOKINETICS OF METHYLPHENIDATE IN MAN, RAT AND MONKEY

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  • 1 January 1983
    • journal article
    • research article
    • Vol. 226  (2) , 382-386
Abstract
The pharmacokinetics and bioavailability of methylphenidate (MPH) and a metabolite, ritalinic acid (RA), were studied in normal adults, children with hyperactivity, monkeys and rats. Adult males received 0.15 or 0.3 mg/kg of MPH orally and MPH and RA were analyzed in plasma samples obtained at various times after treatment. Maximal MPH concentrations in plasma occur 2.2 h after administration of either dose (range: 1.0-4.0). The mean (.+-. SE) maximal concentration in plasma for MPH was 3.5 .+-. 0.4 ng/ml after 0.15 mg/kg and 7.8 .+-. 0.8 ng/ml after 0.3 mg/kg. MPH clearances were high (10.1 l/h per kg) and variable (range: 3.6-23.2) for the 0.3 mg/kg dose. Pharmacokinetic parameters for children receiving 0.3 mg/kg were essentially the same as for adults. RA plasma levels were 50-100 times greater than MPH levels in normal adults. The clearance of RA is less than that of MPH. The abolute bioavailability of MPH was 0.19 in the rat and 0.22 in the monkey, suggesting substantial presystemic elimination of MPH. [MPH is a central stimulant used to treat attentional deficit disorder with hyperactivity and narcolepsy.].