Determination of naltrexone and its major metabolite, 6-beta-naltrexol, in human plasma using liquid chromatography with electrochemical detection.
A sensitive and specific high-performance liquid chromatographic method with electrochemical detection was developed for the simultaneous determination of naltrexone and its major metabolite, 6-beta-naltrexol, in human plasma. After alkalinizing 2 ml plasma samples with pH 9 sodium carbonate buffer, naltrexone and 6-beta-naltrexol were extracted into dichloromethane and then back-extracted into 0.017 M phosphoric acid. A portion of the acid extract was chromatographed on a YMC phenyl column using a mobile phase of methanol-phosphoric acid (50 mM) (20:80, v/v) (pH* 3.2) at a flow-rate of 1.2 ml min 1. Quantification was performed using an ESA Coulometric electrochemical detector. Acceptable intra-day and assay precision (RSD < 10%) and accuracy (< 16%) for both compounds were observed over concentration ranges of 0.25-50.0 ng ml-1 for naltrexone and 0.5-100 ng ml-1 for 6-beta-naltrexol. No degradation of either naltrexone or 6-beta-naltrexol was observed in frozen human plasma stored at -20 degrees C over an 8 month period. The method is sufficiently sensitive and selective to quantify plasma concentrations of naltrexone and 6-beta-naltrexol after oral doses of 50 mg of naltrexone to healthy subjects or alcoholic patients.
Davidson
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AF
Drug Metabolism and Pharmacokinetics Section, DuPont Merck Pharmaceutical Company, Stine-Haskell Research Center, Newark, DE 19714, USA.
Emm
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TA
Pieniaszek
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HJ
D002853:Chromatography, Liquid / Q000379:methods; D004563:Electrochemistry / Q000379:methods; D006801:Humans; D009271:Naltrexone / Q000031:analogs & derivatives* / Q000097:blood*; D009292:Narcotic Antagonists / Q000097:blood*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
D009292:Narcotic Antagonists; C010410:6 beta-hydroxynaltrexone; D009271:Naltrexone