Abstract
Ethylphenidate was recently reported as a novel drug metabolite in two overdose fatalities where there was evidence of methylphenidate and ethanol coingestion. This study explores the pharmacokinetics of ethylphenidate relative to methylphenidate and the major metabolite ritalinic acid, in six healthy subjects who received methylphenidate and ethanol under controlled conditions. Subjects (three males, three females) received a single oral dose of methylphenidate (20 mg; two 10-mg tablets) followed by consumption of ethanol (0.6 g/kg) 30 min later. Methylphenidate, ritalinic acid, and ethylphenidate were quantified using liquid chromatography-tandem mass spectrometry. Ethylphenidate was detectable in the plasma and urine of all subjects after ethanol ingestion. The mean (±S.D.) area under the concentration versus time curve for ethylphenidate was 1.2 ± 0.7 ng/ml/h, representing 2.3 ± 1.3% that of methylphenidate (48 ± 12 ng/ml/h). A significant correlation was observed between the area under the concentration versus time curve of methylphenidate and that of ethylphenidate. In view of the known dopaminergic activity of racemic ethylphenidate, it remains possible that under certain circumstances of higher level dosing, e.g., in the abuse of methylphenidate and ethanol, the metabolite ethylphenidate may contribute to drug effects.
Footnotes
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Send reprint requests to: John S. Markowitz, Pharm.D., Institute of Psychiatry, Rm 338N, Medical University of South Carolina, 67 President St., P.O. Box 250861, Charleston, SC 29425. E-mail:markowij{at}musc.edu
- Abbreviations used are::
- ADHD
- attention-deficit hyperactivity disorder
- CNS
- central nervous system
- LC
- liquid chromatography
- MS
- mass spectrometry
- AUC
- area under the concentration versus time curve
- t1/2
- terminal phase half-life
- Received December 3, 1999.
- Accepted February 1, 2000.
- The American Society for Pharmacology and Experimental Therapeutics
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