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Detection of Ketamine and Norketamine in Urine of Nonhuman Primates after a Single Dose of Ketamine using Microplate Enzyme-Linked Immunosorbent Assay (ELISA) and NCI-GC–MS

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The general anesthetic ketamine (Ketalar®, Ketaject, Vetalar) (KET) is used in human and veterinary medicine for induction of anesthesia for short surgical procedures and routine veterinary examination. Its illicit use by teenagers in rave parties has been reported, and it has recently been identified as a substance associated with sexual assault. One aim of this paper was to study the elimination of KET and its major metabolite norketamine (NKET) in urine collected from five nonhuman primates that received a single dose (5 mg/kg, I.M.) of KET and to study elimination patterns to determine how long after drug administration KET and NKET can be detected. Another aim of this study was to develop and validate a highly sensitive negative ion chemical ionization-gas chromatography–mass spectrometry (NCI-GC–MS) method for the simultaneous quantitation of KET and its major metabolite NKET in urine and to analyze urine samples collected from the animals. The last aim of this study was to apply and evaluate a newly developed ELISA screening methodology for detection of KET and its metabolites in the same urine samples collected from primates which received a single dose of KET. In two monkeys, KET was detected in urine up to 3 days after drug administration (32–7070 ng/mL); in one monkey, it was detected up to 4 days (65–13,500 ng/mL); in one monkey, it was detected only on days 1 and 2 (4000 and 70 ng/mL, respectively); and in one monkey, it was detected 10 days after KET injection (22–35,000 ng/mL). NKET concentrations ranged from 63 pg/mL to 1.75 µg/mL, and it remained in the urine throughout the entire 35-day study period in 4 out of 5 animals. In one monkey, NKET was detected up to 31 days after KET administration. Urine analysis using ELISA revealed that KET and NKET can be easily detectable at 25 ng/mL. In one monkey, KET and its metabolites were detected in urine up to 4 days after drug administration, up to 7 days in two monkeys, up to 11 days in one monkey, and 16 days after KET injection in one monkey. Urine extraction followed by screening using ELISA methodology allowed for significant extension of the detection period in all animals from the study. It is believed that the KET elimination in urine of nonhuman primates is slightly faster than in humans. We propose that NCI-GC–MS be employed to detect NKET as a target compound in urine in toxicological investigations of drug-facilitated sexual assault when KET use by the perpetrator is suspected.

Document Type: Research Article

Affiliations: 1: Department of Biopharmaceutical Sciences, College of Pharmacy, University of Illinois at Chicago, 833 South Wood Street, Chicago, Illinois 60612 2: United States Drug Testing Laboratories, Inc., 1700 South Mount Prospect Road, Des Plaines, Illinois 60018

Publication date: April 1, 2005

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