Two gas liquid chromatographic methods differing mainly in sensitivity are described for the quantitative determination of 2-hydroxy-3-methoxy-6 beta-naltrexol (HMN), a minor metabolite of naltrexone (NT), in human body-fluids. The methods also incorporate simultaneous determinations of naltrexone and its major human metabolite, 6 beta-naltrexol (beta-OL), in urine, serum (or plasma), red blood cells (RBC), and saliva. Flame ionization detection of the bis-(trimethylsylil) trifluoroacetamide (BSTFA) derivatives provided sufficient sensitivity for quantitation of the bases in urine. However, lower levels in serum, RBC and saliva necessitated the use of more sensitive electron capture detection of the pentafluoropropionate (PFPA) derivatives of the bases. Because HMN and 6 beta-naltrexol PFPA derivatives have nearly identical gas chromatographic retention times, their separation was achieved by differential extraction, based on their different partition characteristics between aqueous and organic solvents. In the plasma of 4 subjects, 16 and 24 hrs. after 2 X 200 mg NT doses, the relative percentages were 23.1% HMN, 3.4% NT and 73.5% beta-OL. In urine samples collected at the same time as the blood samples the relative percentages were 14.4% HMN, 9.0% NT and 76.6% beta-OL. The nonpolar nature of HMN and the greater polarity of beta-OL may have influenced their differential distribution into RBCs and saliva. In the RBCs, 96.1% HMN and no significant amount of beta-OL was found, in saliva, 92.3% of beta-OL and no HMN was found.

Results for abused drugs in urine, as obtained by radioimmunoassay (RIA), the "Enzyme Multiplied Immunoassay Technique" ("EMIT"), and hemagglutination inhibition (HI), were compared with each other, with fluorimetry, and with thin-layer chromatography (TLC). The immunoassays and fluorimetric methods were highly sensitive (30 µg/liter to 2 mg/ liter). Cross-reactivity (lack of specificity) varied with the method tested and the drug, ranging from no reaction to one exceeding that of the assay drug. The percentage of false positives for the immunoassays in comparison to TLC ranged from 3 to 31. The practical level of sensitivity for TLC, however, was only 1-5 mg/liter. False negatives were less than 2%. With the EMIT system (for those drug assays for which it is used), the total percentage of false values (negative and positive) ranged from 5 to 13. All the immunoassays were reliable within the limitations of the assay, relatively easy to use, did not require sample treatment, and several hundred samples could be analyzed during an 8-h period; but the cost was moderate to high, depending upon assay or sample volume. Judicious use of immunochemistry, spectrofluorimetry, and thin-layer chromatography to the detection of psychoactive drugs in urine permits rapid, reliable, and effective surveillance of drug use or abuse.

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