PT  - JOURNAL ARTICLE
AU  - W Wargin
AU  - K Patrick
AU  - C Kilts
AU  - C T Gualtieri
AU  - K Ellington
AU  - R A Mueller
AU  - G Kraemer
AU  - G R Breese
TI  - Pharmacokinetics of methylphenidate in man, rat and monkey.
DP  - 1983 Aug 01
TA  - Journal of Pharmacology and Experimental Therapeutics
PG  - 382--386
VI  - 226
IP  - 2
4099  - http://jpet.aspetjournals.org/content/226/2/382.short
4100  - http://jpet.aspetjournals.org/content/226/2/382.full
SO  - J Pharmacol Exp Ther1983 Aug 01; 226
AB  - 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 were found to occur 2.2 hr after administration of either dose (range: 1.0-4.0). The mean (+/-S.E.) 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 liters/hr/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 to 100 times greater than MPH levels in normal adults. The clearance of RA is less than that of MPH. The absolute bioavailability of MPH was found to be 0.19 in the rat and 0.22 in the monkey, suggesting substantial presystemic elimination of MPH.