Hair analysis for ketamine and its metabolites

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Abstract

A rapid and sensitive method was developed for the simultaneous identification and quantitation of ketamine (K) and its major metabolite, norketamine (NK) in hair. After decontamination, the hair sample was incubated and extracted, and analyzed by gas chromatography–mass spectrometry (GC–MS). Limits of quantitation were found to be 0.05 ng/mg. Hair segments in black color were collected from 15 K abusers. Based on an experiment with 15 cavies with black, white, and brown hair, the mechanism of incorporation of K into hair was investigated. After shaving hair on the back of the cavies (8 cm × 4 cm), they were separated into three groups and administered intraperitoneally once a day for 7 successive days with high, medium, and low doses of K, respectively. Two days after this, hair segments with different colors were shaved. There was a direct correlation between the concentration of K in cavy hair and the dose and DHNK was detected only in high dosage group. The concentration of K increased in the order of white, brown, and black hair. The possible factors responsible for the incorporation of K and its metabolites in hair were discussed.

Introduction

Ketamine (K), also called K powder in China, is a rapid-acting dissociative anesthetic used on both animals and humans. K, including its salts or preparations, has been classified as a Class One psychotropic drug. It is abused by an increasing number of young people as a “club drug,” and is often distributed at “raves” and parties. Teenagers are the major abusers. This leads to an increase in crime. After entering the body, K is N-demethylated to norketamine (NK), and then converted to dehydronorketamine (DHNK) and other metabolites through liver [1], [2].

The rapid development of sensitive analytical instruments has enabled the determination of drugs in hair. Compared to the traditional biological materials such as blood and urine, hair has particular advantages, such as easy collection, non-invasiveness, ease of control and storage, good stability, and long detection period that could be up to several weeks, months, or even years. Numerous forensic applications have been described in the literature the values of hair analysis in toxicological examinations [3]. Some papers reported the analysis of K in hair. Sporkert and Pragst [4] analyzed many lipophilic basic drugs including ketamine in hair with headspace solid-phase microextraction followed by gas chromatography–mass spectrometry (HS-SPME–GC–MS). Gentili et al. [5] performed a new HS-SPME–GC–MS procedure for the simultaneous detection of cocaine, amphetamines, and ketamine in human hair and applied to hair samples obtained on a voluntary basis from 183 young people (138 males and 45 females). Leong et al. [6] presented a method for the detection of ketamine in hair using gas chromatography–mass spectrometry and observed a correlation between the amount of ketamine detected and the frequency of abuse. Previously, our lab has used GC and GC–MS for the analysis of K and its metabolites in urine [7]. Herein, we describe a method to analyze K and its metabolites in hair from cavies and drug abusers in entertainment places by using GC–MS; and further elucidated and discussed the characteristics of K incorporation into hair.

Section snippets

Standards and reagents

K, NK, and K-d4 (internal standard) in methanol were purchased from Cerilliant Corporation. Other reagents were all analytical grades and purchased from Sinopharm Chemical Reagent Co. Ltd., Shanghai. K HCl injection solution (0.1 g/mL) used for cavies was obtained from Shanghai Zhongxi Pharmacy Co. Ltd.

Instrumentation

A gas chromatography 6890 Plus with Mass Selective Detector 5973N (Agilent Technologies) was equipped with an HP-5 capillary column (30 m × 0.25 mm × 0.25 um). Helium was used as the carrier gas at a

Results and discussion

In this study, cavy or human hair was subjected to acid hydrolysis, extraction with diethyl ether and was analyzed by GC–MS-SIM. With the use of K-d4 as internal standard, good linear calibration curves in the range of 0.05–100 and 0.05–10 ng/mg were obtained for K and NK, respectively, with correlation coefficients greater than 0.99 (Table 2). The accuracy and precision of the method were tested at 0.4 and 2 ng/mg with satisfactory results (Table 3). As there was no DHNK standard sample

Conclusions

A rapid, sensitive, and specific method was developed for the detection and quantification of K and its metabolites in hair. From the experiment on cavies, the concentrations of K and its metabolites in hair were found to be related to dosage, melanin affinity, and lipophilicity where the deposition of K was highest, compared with its metabolites. As studies on ketamine in hair are quite limited, the use of animal tests such as cavies in our study under controlled conditions might be useful in

Acknowledgments

The authors would like to express their gratitude to Dr. Wing-chi Cheng, Government Laboratory of HKSAR, for his valuable discussion and proofreading of the manuscript. This work has been supported by a grant from Shanghai Science and Technology Commission, PR China.

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