Biomedical Mass Spectrometry 1975, 2. 204 to 205

Metabolites of Phencyclidine in Humans LAN K. WONG and K. BIEMANN

Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 021 39, USA

(Received 27 May 1975)

Abstract--A N-dealkylated metabolite. I -phenylcyclohexylamine, was detected in a urine sample of a patient who had ingested phencyclidine. The identification was facilitated by a feeding experiment using a mouse administered a 1 : I mixture of unlabeled and phenyl-d,-labeled drug. A control experiment was also performed in which a mouse was fed only the unlabeled drug. Two hydroxylated metabolites were also identified in human urine samples. One of the hydroxylated metabolites has a hydroxy group located at the piperidine moiety of phencyclidine while the other has the hydroxy group located at the cyclohexane ring of the drug. It was also shown that l-phenyl- cyclohexene detected in the human samples, was an artifact which arose from pyrolysis of phencyclidine during gas chromatography

Introduction

PHENCYCLIDINE (l), an anesthetic agent, has been discontinued for human usage since 1967 due to its many undesirable side-effects, noticeably hallucination and disorientation.’ Since then the drug has been approved only for use in veterinary medicine. However, in recent years, phencyclidine has appeared as a ‘street drug’ under the names ‘angel dust‘ and ‘peace pill’.’ During the course of the emergency drug analysis service provided by our l a b ~ r a t o r y , ~ we have en- countered numerous cases of phencyclidine intoxication which provided us with an opportunity to search for the metabolites of this drug in humans.

Experimental

Preliminary examination by gas chromatography mass spectrometry (g.c.m.s.) of the blood and urine samples obtained from patients who had ingested phencyclidine did not reveal any metabolites other than the parent drug. This seemed to indicate that the metabolites, if any, were present at very low concen- tration. In order to facilitate the identification of metabolites in humans, the drug was fed to test animals in the hope of identifying the metabolites of phen- cyclidine in that system. Once the compounds are identified in this way, knowledge of their gas chromat- ographic behavior and mass spectral data would greatly facilitate the detection of these compounds even at very low concentration.

D

1 2

Phencyclidine-phenyl-d, (2) was synthesized4 and a 1 : 1 mixture of the labeled and unlabeled drug was administered orally to a mouse. The urine was collected for 36 h, extracted and analyzed by g.c.m.s. Metabolites were identified by inspecting the mass spectra which exhibited the expected isotopic doublets differing by five mass units. A control experiment was also per- formed in which a mouse was fed only the unlabeled drug.

Results and discussion

The g.c.m.s. data of the feeding experiments revealed several components, most of which turned out to be mono or dihydroxy derivatives of 1.7 With this in- formation, the data of the human samples were re- examined. Only a few of the hitherto unknown metabo- lites were found in human urine. For example, in one specimen a trace of metabolite 3 was detected based on the mass spectrum recorded at its proper retention time5 (retention index6 1690).

3 4

Using an enhancement technique recently developed in our laboratory,’ the spectrum shown in Fig. l(a) was generated from the raw data. It clearly exhibits the major feature of the spectrum [Fig. l(b)] of the dealkylated metabolite (1 -phenylcyclohexylamine, 3) identified in the animal experiment. The molecular weight (1 75 a.m.u.) corresponds to the loss of 68 mass

t Detailed data of these components and the interpretation of their mass spectra will be published elsewhere.

0 Heyden & Son Ltd, 1975 204

L. K. WONG AND K . BIEMANN 205

I U

I00

1

I75 I

200

132

1 75 I

M=175

1 75

1 , , ,, , , , , I " '

100 200

t FIG. 1. (a) Mass spectrum of metabolite 3 detected in human urine: (b) Mass spectrum of metabolite 3 detected in mouse; (c) Mass

spectrum of 1 -phenylcyclohexylamine (Aldrich Chemical Co.).

units from the parent molecule (1) and this is most compatible with the loss of (CH,), by dealkylation. The fragment of m/e 132 [M - 431 is analogous to that of m/e 200 in 1,* where it is formed by elimination of C3H7 from the cyclohexyl ring. Thus, this compound was assigned the structure of N-dealkylphencyclidine, i.e. 1-phenylcyclohexylamine (3). This assignment was confirmed by comparison of the spectrum [Fig. l(c)] with that of an authentic specimen commercially available from Aldrich Chemical Co.

Along with this N-dealkylated metabolite, two hydroxylated metabolites were also detected in the human samples. This was concluded by comparison of their mass spectra with that of phencyclidine. Both compounds have molecular ions which are 16 mass units higher than that of phencyclidine. The fragmen- tation pattern of one of them suggested that it has a hydroxy group at the piperidine ring. The mass spectral data, however, could not distinguish between a 3- hydroxy or a 4-hydroxy isomer. It is worthy of noting that Ober' identified a 4-hydroxypiperidyl metabolite in monkey using radioactive isotope techniques. Thus, it is very likely that the metabolite in question is 1 -( 1 -phenylcyclohexyl)-4-hydroxy-piperidine. The mass spectral data of the other hydroxylated metabolite suggested that a hydroxy group is located at the cyclo- hexyl moiety. Again the position of the hydroxy function was not certain, though the 3-isomer is favoured. These compounds are presently being synthesized in order to confirm the structures of these metabolites.

In addition to the above metabolites, l-phenylcyclo- hexene (4) was also identified in these experiments. This component, however, was shown not to be a metabolite, but is an artifact due to pyrolysis of phen- cyclidine in the injection port of the gas chromatograph when operated at temperatures above 150°C.

ACKNOWLEDGEMENT

This work is supported by a grant (RR00317) from the National Institutes of Health, Biotechnology Resources Branch, Division of Research Resources.

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