The 2,5-Dimethoxyamphetamines – A new Class of Designer Drugs

Studies on the Metabolite Identification, Toxicological Analysis, Involvement of Cytochrome P450 Isoforms in

Main Metabolic Steps, and Inhibition Potentials on Cytochrome P450 2D6

Dissertation

zur Erlangung des Grades

des Doktors der Naturwissenschaften

der Naturwissenschaftlich-Technischen Fakultät III -

Chemie, Pharmazie und Werkstoffwissenschaften

der Universität des Saarlandes

von

Andreas Heinrich Ewald Saarbrücken

2008

The 2,5-Dimethoxyamphetamines – A new Class of Designer Drugs

Studies on the Metabolite Identification, Toxicological Analysis, Involvement of Cytochrome P450 Isoforms in

Main Metabolic Steps, and Inhibition Potentials on Cytochrome P450 2D6

Dissertation

zur Erlangung des Grades

des Doktors der Naturwissenschaften

der Naturwissenschaftlich-Technischen Fakultät III -

Chemie, Pharmazie und Werkstoffwissenschaften

der Universität des Saarlandes

von

Andreas Heinrich Ewald

Saarbrücken

2008

Tag des Kolloquiums: 05. 12. 2008

Dekan: Univ.-Prof. Dr. U. Müller

Berichterstatter: Univ.-Prof. Dr. Dr. h.c. H. H. Maurer

Univ.-Prof. Dr. R. W. Hartmann

Die folgende Arbeit entstand unter der Anleitung von Herrn Professor Dr. Dr. h.c.

Hans H. Maurer in der Abteilung Experimentelle und Klinische Toxikologie der

Fachrichtung 2.4 Experimentelle und Klinische Pharmakologie und Toxikologie der

Universität des Saarlandes in Homburg/Saar von Januar 2004 bis November 2007.

Mein besonderer Dank gilt:

Herrn Prof. Dr. Dr. h.c. Hans H. Maurer für die Aufnahme in seinen Arbeitskreis, die

Vergabe eines interessanten und abwechslungsreichen Dissertationsthemas, die

Möglichkeit des selbstständigen Arbeitens, die Möglichkeit der aktiven Teilnahme

und Präsentation auf internationalen Fachkongressen und die

Diskussionsbereitschaft zu jeder Tages- und Nachtzeit,

Herrn Prof. Dr. Rolf Hartmann für die Übernahme des Koreferats,

Frau Prof. Dr. Dorothea Ehlers von der Firma cc chemical consulting, Herrn Dr.

Giselher Fritschi vom Hessischen Landeskriminalamt, Herrn Dr. Michael Pütz vom

Bundeskriminalamt und Herrn Dr. Wolf-Rainer Bork vom Landeskriminalamt Berlin

für die Bereitstellung eines Teils der untersuchten Substanzen und für ihre

Unterstützung bei speziellen Fragestellungen,

Herrn Dr. Frank T. Peters für seine moralische Unterstützung und für seine

wissenschaftliche Expertise und ständige Diskussionsbereitschaft,

Herrn Dr. Denis S. Theobald für die Einführung in die Isoenzym-Bestimmungen und

die kritische Diskussion,

meinen Kollegen für die freundschaftliche Atmosphäre, gute Zusammenarbeit und

die Unterstützung in schwierigen Situationen in der Dienstbereitschaft,

Herrn Armin Weber für seine ständige Einsatzbereitschaft, Wartung und Reparatur

der Messgeräte sowie Rat bei technischen Fragestellungen,

Frau Gabriele Ulrich für gewissenhaft ausgeführte Laborarbeiten,

meiner Frau Julia, die mir den Rücken frei gehalten und immer zu mir gehalten hat,

meiner Familie, insbesondere meinen Eltern, die mich in meinem Tun stets gefördert

und unterstützt haben,

meinen Freunden und Bekannten, die in den letzten Jahren des Öfteren ohne mich

auskommen mussten.

Julia

und meinen Eltern

TABLE OF CONTENTS

1 GENERAL PART 1

1.1 Introduction 1

1.1.1 The 2,5-Dimethoxyamphetamine Derived Designer Drugs 1

1.1.2 The Cytochrome P450 System 3

1.2 Aims and Scopes 8

2 PUBLICATIONS OF THE RESULTS 9

2.1 Designer drugs 2,5-dimethoxy-4-bromo-amphetamine

(DOB) and 2,5-dimethoxy-4-bromo-methamphetamine

(MDOB): Studies on their metabolism and toxicological

detection in rat urine using gas chromatographic/mass

spectrometric techniques50

(DOI:10.1002/jms.1007) 9

2.2 Designer drug 2,4,5-trimethoxy-amphetamine (TMA-2):

Studies on its metabolism and toxicological detection

in rat urine using gas chromatographic/mass

spectrometric techniques51

(DOI:10.1002/jms.1059) 23

2.3 Metabolism and toxicological detection of the designer

drug 4-iodo-2,5-dimethoxy-amphetamine (DOI) in rat

urine using gas chromatography-mass spectrometry52

(DOI:10.1016/j.jchromb.2007.06.027) 35

2.4 Designer drug 2,5-dimethoxy-4-methyl-amphetamine

(DOM, STP): Involvement of the cytochrome P450

isoenzymes in formation of its main metabolite and

detection of the latter in rat urine as proof of a drug

intake using gas chromatography-mass spectrometry53

(DOI:10.1016/j.jchromb.2007.11.042) 43

2.5 Metabolism and toxicological detection of the designer

drug 4-chloro-2,5-dimethoxyamphetamine in rat urine

using gas chromatography-mass spectrometry54

(DOI:10.1007/s00216-008-1917-z) 51

2.6 2,5-Dimethoxyamphetamine-derived designer drugs:

Studies on the identification of cytochrome P450 (CYP)

isoenzymes involved in formation of their main

metabolites and on their capability to inhibit CYP2D655

(DOI:10.1016/j.toxlet.2008.09.014) 59

3 CONCLUSIONS 87

4 SUMMARY 89

5 REFERENCES 91

6 ABBREVIATIONS 95

7 ZUSAMMENFASSUNG 97

1 GENERAL PART

1.1 INTRODUCTION

1.1.1 The 2,5-Dimethoxyamphetamine Derived Designer Drugs

Consumption of drugs of abuse is a widespread problem in societies all over the

world. Especially, so-called designer drugs are becoming more and more popular

among young people. The most frequently abused drugs are amphetamine,

methamphetamine and their derivatives, such as 3,4-methylenedioxyamphetamine

(MDA), 3,4-methylenedioxymethamphetamine (MDMA, “Ecstasy”), para-methoxy-

amphetamine (PMA), and para-methoxymethamphetamine (PMMA). However,

during the 1990s, the illicit drug market for recreational drugs changed considerably

with several new types of drugs appearing on the drug scene. Information about

these new drugs is readily available and they can even easily be purchased via the

internet.1

One of these new classes of drugs of abuse are the 2,5-dimethoxyamphetamines.

Typical drugs of this class are 4-bromo-2,5-dimethoxyamphetamine (DOB), 4-chloro-

2,5-dimethoxyamphetamine (DOC), 4-iodo-2,5-dimethoxyamphetamine (DOI), 2,5-

dimethoxy-4-methyl-amphetamine (DOM), 4-bromo-2,5-dimethoxymethamphetamine

(MDOB), and 2,4,5-trimethoxyamphetamine (TMA-2). Their chemical structures are

shown in Fig. 1.

Fig. 1: Chemical structures of amphetamine-derived designer drugs.

- 1 -

They all have in common an amphetamine structure containing two methoxy groups

in positions 2 and 5 of the aromatic ring and a different lipophilic 4-substituent.

MDOB as the methamphetamine analogue of DOB contains an additional methyl

moiety at the nitrogen.

Introducing new substituents allows the drug abusers to create “legal” products which

are not scheduled as controlled substances. Most of the 2,5-

dimethoxyamphetamines were synthesized by Alexander Shulgin and described in

his compilation “PIHKAL”.2 This work contains the structures of the 2,5-

dimethoxyamphetamines, their hallucinogenic potency, effects, dosage and their

synthesis. Because of this it is relatively easy for the illicit drug producers to

manufacture a new 2,5-dimethoxyamphetamine entity when another one is

scheduled. The first synthesized of the studied drugs was TMA-2 in 19473 and it was

sold under the name “Zerox”. In 1967 DOM appeared on the illicit drug market

especially in the “hippie scene” in San Francisco under the name STP, which was

said to stand for Serenity, Tranquility, and Peace. Street names of DOB were

“Golden Eagle” or “LSD-25”. Although many 2,5-dimethoxyamphetamines were first

synthesized during the 1970s, they gained increasing popularity in the late 1990s and

the beginning of this century after the publication of “PIHKAL”. They were sold in so-

called “smart shops” alone or in mixture with other designer drugs in form of tablets,

powder, liquids or blotters. This trend was accompanied by seizures of tablets

containing 2,5-dimethoxyamphetamines or combinations of them with other drugs by

the police. Because of the high abuse potential of the 2,5-dimethoxyamphetamines,

many of them were scheduled in most countries and by the UN in the convention on

psychotropic substances in 19714. DOB became quite popular as a drug of abuse,

especially in Australia, Italy, and the USA5-10 At present, DOI and DOC, which are not

scheduled in the USA, and TMA-2 are entering the illicit drug market, as indicated by

seizures11-19 and experience reports on so-called drug information web sites

(http//:www.erowid.org, http//:www.lycaeum.org; September 2008). Some information

is available on pharmacological properties of the 2,5-dimethoxyamphetamines. They

show affinity to 5-HT2 receptors and act as agonists or antagonists at different

receptor subtypes.20-25 Because of the high potency and selectivity of DOI as 5-HT2

receptor agonist and the fact that it was not scheduled until now and is commercially

available, it was used in research when a selective 5-HT2 receptor agonist was

needed.26,27

- 2 -

The chemical structure responsible for the hallucinogen-like activity comprises a

primary amine functionality separated from the phenyl ring by two carbon atoms, the

presence of methoxy groups in position 2 and 5 of the aromatic ring, and a

hydrophobic 4-substituent (alkyl, halogen, alkylthio, etc.).25 The methyl moiety in

α-position to the nitrogen atom is reported to be responsible for increased in vivo

potency and duration of action.25

For some 2,5-dimethoxyamphetamines, analytical data are available.28,29 A GC/MS

procedure was described for detection of DOB and DOM (parent compounds), and

other amphetamine derivatives but not for the other studied drugs.30

However, for developing toxicological screening procedures, especially in urine, it is

a prerequisite to know the metabolism of the compounds in question, especially if

they are excreted in urine primarily or even exclusively in form of metabolites.

Furthermore, data on the metabolism are needed for toxicological risk assessment,

because the metabolites may play a major role in the toxicity of a drug.

One metabolism study in humans after intoxication related to DOB has been

reported.31

Besides the direct toxicity of a drug or a metabolite, inhibition of metabolizing

enzymes could also lead to toxic effects due to possible overdoses after co-

administration of different substances which were metabolized by the same enzyme.

Some studies about the inhibition properties of amphetamine analogues on CYP2D6

have been published.32-36

1.1.2 The Cytochrome P450 System

Most drugs are metabolized by a variety of enzymes, and these metabolic processes

can generally produce metabolites that are usually less toxic than the parent

compound. The metabolites may also be more reactive, producing toxic effects. The

metabolic profiling of drugs is, therefore, necessary to assess their effects and

toxicity.37 Cytochrome P450 (CYP) enzymes are responsible for oxidative and, to a

- 3 -

minor extent, reductive metabolic transformations of drugs, environmental chemicals

and natural compounds. Over its long history of more than 3.5 billion years, the CYP

superfamily of enzymes has developed remarkable versatility. The primary catalytic

function of CYPs was identified as transfer of one oxygen atom from molecular

oxygen into various substrates (Fig. 2). A coenzyme, cytochrome P450

oxidoreductase (OR), is essential for CYP catalytic function, and cytochrome b5 can

stimulate catalytic activities of some enzymes.38

Fig. 2: The cytochrome P450 redox cycle.

Single electron shifts are frequently responsible for the formation of reactive

intermediates or allow the leakage of free radicals capable of causing toxicity. When

a CYP enzyme activity is modified by induction or inhibition, the biological activity of

the xenobiotic substrate can be altered considerably. Such effects are called drug-

drug, drug-chemical or chemical-chemical-interactions. Such interactions can modify

the disposition of xenobiotics.39-41 CYPs are heme-containing, membrane-bound

enzymes (“heme-thiolate proteins”) detected in both prokaryotes and eukaryotes.

The enzymes were given their names because their complexes with carbon

monoxide under reductive conditions show an absorbance maximum at about

- 4 -

450 nm. In mammals the enzymes can be identified in nearly every tissue, being

most abundantly present in the liver. The CYP superfamily has been classified in

different families in accordance to the degree of homology of amino acid sequence in

their protein structures. CYP enzymes having ≤ 40% homology in their amino acid

sequence are classified in different families which are designated by Arabic numbers,

for example, CYP1. Each family is further divided into subfamilies of enzymes. The

enzymes within a mammalian subfamily have ≥ 55% sequence homology and are

designated by capital letters, for example, CYP1A. An Arabic number is used for

designating individual enzymes within a subfamily, for example, CYP1A2.39 In

humans, 18 CYP families with 43 subfamilies and 57 CYP isoenzymes are known so

far, of which only 3 families with 7 subfamilies and 12 CYP isoenzymes are relevant

for drug metabolism (Fig. 3),42 namely CYP1A1, CYP1A2, CYP2A6, CYP2B6,

CYP2C8, CYP2C9, CYP2C18, CYP2C19, CYP2D6, CYP2E1, CYP3A4, and

CYP3A5.43

Fig. 3: Cytochrome P450s found in humans and their relevance in xenobiotic metabolism. Modified according to ref.43

Polymorphisms of clinical relevance

- 5 -

The remainder is responsible for the transformation of endogenous biomolecules, for

which reason they are called “housekeeping enzymes”. Fig. 4 illustrates the

abundances of CYPs in human liver and their importance in xenobiotic metabolism.

Some CYP genes are polymorphically expressed, leading to variabilities in patterns

of drug metabolism

Fig. 4: Relative quantities of CYPs in human liver and their relevance in drug metabolism. Left side: human CYP-expression in the liver. Right side: involvement in xenobiotics

metabolism.

Human liver derived enzyme preparations, e.g. human liver microsomes (HLM)

contain a natural mixture of CYPs. Chemical inhibitors, immunochemical inhibitors,

and/or correlation analyses with marker activities must be used to obtain information

on which enzymes are performing specific biotransformations. In contrast, only a

single active CYP is present in preparations of cDNA-expressed enzymes. Inhibitors

and correlation analyses are not needed, because the mentioned assignments can

be performed by direct incubation of the drug with a panel of individual CYPs.

However, the balance of enzymes, present in vivo, is lost.38 Bacteria, yeast,

baculovirus and several mammalian cells have been used to produce a wide range of

catalytically active CYPs. The baculovirus system offers high-level expression of both

the CYP and OR, and are therefore advantageous for metabolism studies of all

kinds, especially for low turnover substrates. The development of the cDNA-bearing

virus is relatively time-consuming and labor-intensive, but baculovirus infected insect

cell microsomes are commercially available. However, because the enzymes are

produced transiently in the insect host cells, exact harvest time can have a

pronounced effect on the activity of the final preparation.44

Identification of the human enzymes involved in the metabolism of specific drugs is

becoming increasingly important for drug development. Such identifications should

- 6 -

consider two processes involving the new drug: metabolism and inhibition. The

identification of enzymes involved in metabolism of the new drug allows prediction,

based on knowledge of the ability of co-administered drugs to inhibit the same

enzymes, of which co-administered drugs may inhibit the metabolism of the new

drug. This information can also be used to predict individual variability based on

known metabolic polymorphisms.38 However, also the new drug can act as an

inhibitor what may lead to interactions with co-administered drugs.

- 7 -

1.2 AIMS AND SCOPES

In clinical cases where an unknown substance was ingested (e.g. poisonings), the

identity of this substance has to be clarified to be able to start suitable medical

treatment and to make statements on the clinical outcome. Also in forensic cases,

intake of an illegal drug has to be proven. Usually, a general unknown screening is

performed in urine, where the concentrations of the parent compound/and or its

metabolites are higher than in blood or plasma and the taken drugs or toxicants can

be detected for several hours or even days after ingestion, in contrast to blood

analysis which covers only a few hours.45,46 Knowledge about metabolic steps is a

prerequisite for developing toxicological screening procedures, especially, if the

compounds are excreted in urine only in form of their metabolites.

The knowledge of the involvement of particular CYP isoenzymes in the

biotransformation of a new drug is a prerequisite to predict possible drug-drug-

interactions, inter-individual variations in pharmacokinetic profiles and increased

appearance of side effects and serious poisonings.47,48 Inhibition capabilities for CYP

isoenzymes by new drugs are also sources for drug-drug-interactions which should

be examined. However, such risk assessment is typically performed for substances

intended for therapeutic use, but not for drugs of the illicit market. In addition, there is

good evidence that genetic variations in drug metabolism have important behavioral

consequences that can alter the risk of drug abuse and dependence.49 The 2,5-

dimethoxyamphetamines were not yet investigated in any of these respects, so that

the aims of the presented studies were:

• Identification of the metabolites

• Development of a urine screening procedure

• Identification of the cytochrome P450 isoforms involved in the main metabolic

steps

• Determination of the inhibition potentials on cytochrome P450 2D6

- 8 -

2 PUBLICATIONS OF THE RESULTS

The results of the studies were published in the following papers:

2.1 DESIGNER DRUGS 2,5-DIMETHOXY-4-BROMO-AMPHETAMINE (DOB) AND

2,5-DIMETHOXY-4-BROMO-METHAMPHETAMINE (MDOB): STUDIES ON

THEIR METABOLISM AND TOXICOLOGICAL DETECTION IN RAT URINE USING

GAS CHROMATOGRAPHIC/MASS SPECTROMETRIC TECHNIQUES50 (DOI:10.1002/JMS.1007)

- 9 -

2.2 DESIGNER DRUG 2,4,5-TRIMETHOXY-AMPHETAMINE (TMA-2): STUDIES ON

ITS METABOLISM AND TOXICOLOGICAL DETECTION IN RAT URINE USING GAS

CHROMATOGRAPHIC/MASS SPECTROMETRIC TECHNIQUES51 (DOI:10.1002/JMS.1059)

- 23 -

2.3 METABOLISM AND TOXICOLOGICAL DETECTION OF THE DESIGNER DRUG 4-IODO-2,5-DIMETHOXY-AMPHETAMINE (DOI) IN RAT URINE USING GAS

CHROMATOGRAPHY-MASS SPECTROMETRY52 (DOI:10.1016/J.JCHROMB.2007.06.027)

- 35 -

2.4 DESIGNER DRUG 2,5-DIMETHOXY-4-METHYL-AMPHETAMINE (DOM, STP): INVOLVEMENT OF THE CYTOCHROME P450 ISOENZYMES IN FORMATION OF

ITS MAIN METABOLITE AND DETECTION OF THE LATTER IN RAT URINE AS

PROOF OF A DRUG INTAKE USING GAS CHROMATOGRAPHY-MASS

SPECTROMETRY53 (DOI:10.1016/J.JCHROMB.2007.11.042)

- 43 -

2.5 METABOLISM AND TOXICOLOGICAL DETECTION OF THE DESIGNER DRUG

4-CHLORO-2,5-DIMETHOXYAMPHETAMINE IN RAT URINE USING GAS

CHROMATOGRAPHY-MASS SPECTROMETRY54 (DOI:10.1007/S00216-008-1917-Z)

- 51 -

2.6 2,5-DIMETHOXYAMPHETAMINE-DERIVED DESIGNER DRUGS: STUDIES ON

THE IDENTIFICATION OF CYTOCHROME P450 (CYP) ISOENZYMES

INVOLVED IN FORMATION OF THEIR MAIN METABOLITES AND ON THEIR

CAPABILITY TO INHIBIT CYP2D655 (DOI:10.1016/J.TOXLET.2008.09.014)

- 59 -

3 CONCLUSIONS

The studies presented here show that the 2,5-dimethoxyamphetamine designer

drugs DOB, DOC, DOI, MDOB, and TMA-2 were mainly metabolized by O-

demethylation, and in case of DOM by hydroxylation. Further steps were the side

chain hydroxylation and the oxidative deamination. As metabolic phase II reactions

partial glucuronidation and sulfation were observed. Furthermore, combinations of

these steps as well as minor metabolites were also detected.50-53,55

The developed screening procedures allowed the detection of the studied 2,5-

dimethoxyamphetamine in rat urine after administration of common drug abusers'

doses mainly via their metabolites.

In vitro studies showed that CYP2D6 was the only isoform catalyzing the

demethylation of the DOB, DOC, DOI, MDOB, and TMA-2 and the hydroxylation of

DOM. Besides the drugs were substrates of CYP2D6 inhibition properties on

CYP2D6 could also be observed.53,55

This detailed knowledge of the metabolic steps of designer drugs and the inhibition

potential on CYP2D6 is an important prerequisite for assessing possible interaction

with other drugs or food ingredients as well as inter-individual pharmacogenetic

differences. These pharmacogenetic differences due to poor or ultra rapid

metabolizers are shown especially by CYP2D6 which is polymorphically expressed.

Besides CYP2D6 is the only enzyme catalyzing the studied metabolic steps and is

also inhibited by the drugs, this enzyme is involved in metabolism of many

pharmaceuticals so the possibility of drug-drug interaction is given but unlikely due to

the high inhibition constants of the drugs. Whether these possible interactions are of

clinical relevance can not be concluded at the moment. However, further clinical

studies would be necessary to predict the risk of interactions. Also studies on the

pharmacology and toxicology of the metabolites together with well documented

clinical data will be necessary.

- 87 -

4 SUMMARY

In the presented studies, the metabolism and the toxicological analysis in urine of the

amphetamine-derived designer drugs DOB, DOC, DOI, DOM, MDOB and TMA-2

were investigated. Furthermore, CYP isoform dependence of the main metabolic

steps and the inhibition potential of the parent drugs on CYP2D6 were elucidated to

predict possible drug-drug interactions and influence of genetic polymorphisms. The

2,5-dimethoxyamphetamines were mainly metabolized by O-demethylation in

position 2 and 5 of the ring, respectively, and by deamination followed by reduction to

the corresponding alcohol. A further metabolic step was the hydroxylation of the side

chains. Phase II reactions consisted of partial glucuronidation and/or sulfation.

Combinations of these steps could also be detected. The target analytes for the

toxicological analysis were the derivatized hydroxy metabolite of DOM or the O-

demethyl metabolites of DOB, DOC, DOI, MDOB and TMA-2. CYP2D6 was identified

to be the only CYP isoform involved in the main metabolic steps. In addition, the

studied drugs act also as inhibitor of CYP2D6. It could be shown, that the mode of

inhibition of none of the studied drugs was irreversible, but competitive for all drugs.

- 89 -

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main metabolites and on their capability to inhibit CYP2D6. Toxicol. Lett. 2008; DOI:10.1016/j.toxlet.2008.09.014

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6 ABBREVIATIONS

DOB 4-bromo-2,5-dimethoxyamphetamine

DOC 4-chloro-2,5-dimethoxyamphetamine

DOI 4-iodo-2,5-dimethoxyamphetamine

DOM 2,5-dimethoxy-4-methylamphetamine

MDOB 4-bromo-2,5-dimethoxymethamphetamine

TMA-2 2,4,5-trimethoxyamphetamine

CYP cytochrome P450

GC-MS gas chromatography-mass spectrometry

LC-MS liquid chromatography-mass spectrometry

FAD flavin adenine dinucleotide

5-HT 5-hydroxytryptamine (serotonin)

cDNA copy deoxyribonucleic acid

Km substrate concentration at half of the maximal turnover rate

MDA 3,4-methylenedioxyamphetamine

MDMA 3,4-methylenedioxymethamphetamine

OR oxidoreductase

PMA para-Methoxyamphetamine

PMMA para-Methoxymethamphetamine

Vmax maximal turnover rate

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7 ZUSAMMENFASSUNG

Im Rahmen dieser Dissertation wurden der Metabolismus und die Nachweisbarkeit

der neuen Designerdrogen des Amphetamin-Typs DOB, DOC, DOI, DOM, MDOB

und TMA-2 im Urin untersucht. Um mögliche Interaktionen oder Einflüsse

genetischer Polymorphismen abzuschätzen, wurde darüber hinaus untersucht,

welche Cytochrom P450 (CYP) Isoenzyme die Hauptmetabolismusschritte

katalysieren und ob die Drogen CYP2D6 inhibieren können. Die 2,5-

Dimethoxyamphetamine wurden hauptsächlich durch O-Demethylierung in Position 2

bzw. 5 des Ringes oder durch Deaminierung gefolgt von Reduktion zum

entsprechenden Alkohol metabolisiert. Weitere Metabolismusschritte waren die

Seitenkettenhydroxylierung. Als Phase-II-Reaktionen konnten partielle

Glucuronidierung oder Sulfatierung gefunden werden. Metabolite aus Kombinationen

dieser Schritte konnten ebenso detektiert werden. Die derivatisierten Metabolite der

Drogen aus den Hauptstoffwechselwegen (O-Demethylierung bei DOB, DOC, DOI,

MDOB und TMA-2; Hydroxylierung bei DOM) waren die Zielsubstanzen im

toxikologischen Nachweisverfahren. Für CYP2D6 konnte als einzige Cytochrom

P450 Isoform eine Beteiligung an den Hauptstoffwechselwegen nachgewiesen

werden. Neben der Verstoffwechselung der untersuchten Substanzen durch

CYP2D6 konnten auch eine Hemmung dieses Enzyms durch diese Substanzen

beobachtet werden. Es wurde gezeigt, dass keine der untersuchten Substanzen eine

irreversible sondern eine kompetitive Hemmung bewirkte.

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