drugs & driving - a screening system and a survey of results. · drugs & driving - a...
TRANSCRIPT
Drugs & Driving - a screening system and a survey of results.
J.F. Taylor
M etropolitan Police Forensic Science Laboratory
109 Lam beth Road, London, SE1 7JH, England
Introduction
Drug screening system s are generally dependent upon several limiting
fac to rs . In the forensic toxicological exam ination of samples taken under
the British Road T raffic Act (RTA) the most im portan t a re as follows:
a) The biological samples available for analysis and the ir volumes.
In this Laboratory the samples w ere blood alone (2 m illilitres on average) in
66 per cen t of cases, urine alone (up to 25 millilitres) in 25 per cen t of cases
and blood and urine tog e th e r in 8 per cen t of cases.
b) The classes of drug under exam ination.
In RTA cases we are concerned with those which can impair judgem ent,
psychomotor ac t iv ity e tc . in a way de trim en ta l to driving. This commonly
includes sedatives , tranquill izers , s tim ulan ts , an ti-h is tam ines, an t i
convulsants, an ti-depressan ts , hallucinogens and narcotics .
c) The pa ram ete rs of identif ication .
Normally a t least two independent (uncorrelated) techniques are required
for positive identification . (e.g. TLC and GC or GC and Mass
Spectrom etry). For many drugs d e tec te d in blood by radio-immunoassay
confirm ation poses such a problem th a t it is the subject of a large
proportion of cu rren t research in toxicological analysis.
478
d) The background information available.
In negative or low alcohol RTA cases where drugs analysis is requested , the
following inform ation is routinely sought in the form of a questionnaire to the off icer in the case as follows:
(i) Were there any drugs in the defendant's possession? if so, what?,
where are they now?, could they be subm itted for identification?
(ii) What was the defendant's condition? (e.g. drowsy, asleep, ag ita ted etc).
(iii) Did the police surgeon cert ify im pairm ent?
(iv) Is the subject prescribed any drugs by his own doctor? If so, w hat? ,
when was the last dose taken?, how long has he been taking them ?.
(v) Is the subject a known drug user? (or reg is tered drug addict).
E x trac tion and d e tection of drugs
The general scheme for acidic and neutra l drugs is shown in Figure 1.
Evaporated ex tra c ts are dissolved in acc tone for TLC on silica gel plates in
ch loroform /ace tone (4:1). Spot location is by UV - short wave absorbance
and by spraying with van Urk reagen t (for ca rbam ates and benzodiazepines),
fe rr ic ch loride/ferricyanide reagen t (for paracetam ol etc) and m ercuric
chloride/diphenylcarbazone reagen t (for barb itu ra tes etc). The sam e ex tra c t
is then m ethy la ted with d iazom ethane prior to tem pera tu re programmed GC
on SP2510DA with dual NPD/FID detec tion . Peak identification is based on
re la tive re ten tion to m ethyla ted cyclopal internal standard and d e tec to r
response ra tio followed by GC on Apiezon L and (if necessary) GC-MS. The
general schem e for basic drugs (Figure 2) involves the above mentioned
aliquot of urine. TLC screening is performed on caustic silica gel p lates in
ch lorform /m ethanol (4:1). Spots are located by the ir UV-short wave
absorbance and by spraying separate ly with:
479
(i) NQS (B - naphthaquinone sulphonate) reagent
(ii) dilute sulphuric acid (noting UV long wave fluorescense) followed by
iodoplatinate reagen t.
This ex tra c t is then screened by GC on OV-17 with dual AFID/FID
detec tion . This involves tr ip le te m p era tu re isotherm al screening (150, 200
& 260 C) using respectively n icotine, diphenhydramine and methaqualone
as GC m arkers. Nowadays there a re many basic drugs routinely available
and an associated wide range of vola tility ; th e re fo re this form of isothermal
screening is p re fe rred to te m p era tu re program m ed screening because it is
m ore discriminating and the re la tive re ten tion da ta is m ore reproducible.
The general schem e for de tec tion of benzodiazepines (as benzophenones)
and morphine in urine is described in Figure 3. For benzophenones TLC is
perform ed on caus tic silica gel p la tes using chloroform or to luene as eluting
solvent. Spots are located by the ir yellow colour in daylight and the colours produced with
(i) Bratton-M arshall reagen t and
(ii) m ethanolic paradim ethylam ino - benzaldehyde oversprayed with
m ethanolic tr ich loro - a c e t ic acid.
The TLC system for morphine is identical to th a t described for basic drugs.
The details for blood benzodiazepine screening are described la te r under
batch methods of analysis (Figure 5). R ecen t im provem ents in the gas
chrom atography of benzodiazepines by using OV-7 and OV-225 s ta t ionary
phases instead of OV-17 alone have provided a more comprehensive screen
for the m em bers of this class of drugs plus improved resolution of drugs
from co -ex trac tives arising from the rubber septum cap of the blood
con ta iner . The la t t e r has p e rm itted sim plification of the ex trac tion
procedure and we now use a one-step 30-second "whirlymix" ex trac tion on
100 ul blood using 100 j j l b u ty lace ta te as solvent followed by d irec t
injection of an aliquot of the la t te r onto the GC column.
480
During the period of this survey, the radio-immunoussays routinely used were
those for morphine (Abuscree.n), Cannabinoids, Lysergide (LSD) and diazepam.
Batch m e thod of analysis
Due to the increasing number of RTA cases requiring drugs analysis,
the analysis of those cases involving blood alone in batches of six was
investigated. The schemes for analysis are shown in figures 4 and 5. They
were found to have the advantages of being tim e saving (usually only two
calibrations involved), m ore eff ic ien t in use of machine tim e and more
convenient in th a t they enable comparison of case chrom atogram s and quick
de tec tion of spurious peaks from solvent impurities or biological co
ex trac tives . With careful labelling of ex trac tion and evaporation tubes and
a t ten tion to such details during solvent transfers and analysis, the only
disadvantage appears to be the tedious nature of the batch procedure.
Survey of drugs d e tec te d in 1978 RTA cases
The p a t te rn of frequency of detection of drugs or classes of drug is
shown in figure 6. The benzodiazepine class of drugs is the most prevalent
being encountered in 38 per cent of cases and being in the form of diazepam
in 25 per cen t of cases. Sedatives and tranquillizers account for im pairm ent
in most of the cases and narco tic analgesics were significantly de tec ted in
about 13 per cen t of cases. Cannabis, s tim ulants, anti-h istam ines, an ti
convulsants and an ti-depressants considered as a whole account for only 10
per cen t of the cases. O ther than anti-convulsants, these drugs and classes
of drugs are mainly those which prove difficult to screen for in small blood
samples. The im portance of also having urine subm itted in RTA cases is
emphasized if we com pare percen tage detection of drugs in all RTA drug
cases with th a t in such cases where only blood was subm itted for analysis
(figure 7). With blood alone the percentage detection of s tim ulants, an ti
histamines and an ti-depressants falls to zero. It follows th a t , since two
thirds of all cases involved blood alone, the percen tage overall de tec tion of
these classes of drugs may be a gross underestim ate of their involvement in
RTA cases. Since radio-immunoassays for am phetam ine-type drugs and
tricyclic an ti-depressants becam e com mercially available this situation has
481
partly been rec tif ied , the problem now being one of having suff ic ien t blood
sample to analyse. The reasons for no s ignificant change in percen tage
de tec tion of cannabinoids is th a t RIA forms the sole basis for screening both
blood and urine. There a re also no significant d ifferences in the percen tage
de tec tions for benzodiazepines and for barb itu ra te s . As expec ted the
percen tage de tec tion of "no drugs" is noticeably higher in RTA cases
involving blood alone. A previous survey of this nature indicated a much
higher percen tage "negatives" in cases involving only blood:
1976 (Jan to June) 1978 (Jan to Sept)
RTA cases involving urine 32 49
P ercen tage negative 22 <—j 20 <-i
RTA case involving blood alone 39 17 99 8
Pe rcen tage negative 39
The approxim ate one third reduction in the percen tage negatives for
1978 "blood only" cases is due to im provem ent in analytical techniques and,
in par ticu la r , to the introduction of RIA into casework. Also the much
sm aller d ifference in percen tage negatives betw een "blood only" and "urine"
cases in 1978 prompts one to question the need to analyse urine. An
exam ple of results from an RTA case involving blood and urine (table 1)
shows th a t if blood alone had been analysed, the re would have been an
incom plete pic ture of the defendants multiple drug mis-use. Indeed one can
envisage a com peten t counsel rightly dismissing a positive RIA result for
morphine as being non-specific and also assigning the am ylobarbitone and
quinalbarbitone to being residual from a previous night's hypnotic dose. In
o the r words, it is the overall p ic ture of drug taking which is im portant; not
just the de tec tion of a drug and reporting the case as "positive".
"Drugs and Driving"_and "Drug_Abuse"
Cases such as th a t decribed above have led to an investigation of the
degree to which drug abuse is a fac to r in drugs and driving cases. The
results are given in tab le 2. Information concerning the firs t two categories
of drug abusers was obtained from the previously mentioned questionnaire
for background inform ation. In the third category examples of results taken
as indicating drug abuse would be "positive for re s tr ic ted drug(s)", "unusually
482
high barb itu ra te /m ethaqualone level", "strong detection of diethylpropion" e tc .
The findings indicate tha t 35 per cen t of 1978's drugs and driving
cases in London and surrounding counties involved drug abuse. In all
probability the actual percen tage figure is even higher because blood alone
was subm itted in two thirds of our cases and the re was the re fo re an
incom plete pic ture of overall drug consumption.
The public a t large probably think th a t most drugs and driving cases
involve normal pa tien ts undergoing normal drug therapy who, having
consumed alcohol socially and in moderation, are found to have the ir driving
impaired by such a combination of drink and drug(s). Table 2 shows th a t this
is only known to occur in 11 per cent of cases.
C orre la tion of "drugs and driving" and "drug abuse" trends
S ta tis tics for the past eight years (figure 8) show some degree of
corre la tion betw een increase in "drugs and driving" and "illicit drug
possession". Many fac to rs influence such s ta t is t ic s ; for instance, the degree
of police activ ity towards a particu lar type of crim e. However, the
increased incidence of "drugs and driving" is highlighted by the fac t th a t it
has occurred during a period in which the yearly to ta ls for RTA cases
involving alcohol have markedly decreased. This may be a t tr ibu ted to the
m ore serious consequences of "drugs and driving".
The initial upsurge of "drugs and driving" cases from 1972 is probably
partly due to the introduction of large RTA blood specimens coupled with an
increase in expertise which led to drugs analysis being actively
encouraged in RTA cases where low blood alcohol figures had been reported.
483
This survey has shown th a t drug abuse contributes overwhelmingly to
the drugs and driving cases encountered in M etropolitan and neighbouring
County Constabularies. In o ther large c ities , t ra f f ic acc ident studies have
suggested th a t users (and abusers) of narco tics (1), sedative-hypnotics (2)
and cannabis (3) (4) have driving records which do not d iffer significantly
from those of age-m atched m em bers of the general population. However,
the narco tics study has been crit ic ized because of the na tu re of the control
groups who, although not opia te addicts, may have been users of o the r drugs.
Also the findings in rela tion to sedative hypnotics and cannabis are greatly
disputed by studies showing a considerable over-involvem ent of barb itu ra te
users among drivers in fa ta l acc idents (5) and above-normal acc iden t ra tes
for users of cannabis (6). Laboratory studies of sim ulated driving show th a t
all the drugs or classes of drugs examined in the present survey are capable
of producing im pairm ent (7). The fac t th a t , in this survey, they appear
mainly subject to abuse raises the question: should abusers, who are addicted
to such drugs, be prevented from holding a licence to s ta r t with?
Finally, with regard to the preponderance of benzodiazepine
tranquillizers (especially diazepam ) in this survey, it is suggested th a t they
be included in a class similar to the an ti-h is tam ines such th a t th e re is, by
law, a printed warning of the drug's possible adverse e f fe c t upon driving e tc .
and the contra indication of alcohol on the outside of each prescription
con ta iner . The number of court defences where it is alleged th a t the re was
no similar warning by the defendant's physician suggests th a t this is a
problem which may be b e t te r solved by forensic pharm aceutica l controls
ra th e r than by verbal recom m endations le f t to be passed on from an
overworked and som etim es forgetfu l physician to his ailing pa tien t.
R eference
1. Gordon, N.B., "Drugs and Driving", ed. Moskowitz H., Pergam on
Press, (1976).
Discussion
484
2. Nichols, J.L., Drug Use and Highway Safety: A Review of the
l i te ra tu re , United S ta tes D epartm ent of Transportation, National Highway
Traffic Safety Administration , Washington D.C. (1971).
3. Waller, J.A., New England Journal of Medicine, (1965) 273, 1413 - 1420.
4. Waller, J.A. and Goo, J.T., Journal of Safety Research, (1969) 1, 13 - 27.
5. Report on Alcohol, Drugs and Organic Fac tors in Fa ta l Single Vehicle
Traffic Accidents, S ta te of California Highway Patro l, Final Report, (1967).
6. C rance r, A. and Quiring, D.L., Driving records of people a rres ted for
illegal drug use. Report O il . S ta te of Washington, D epartm ent of Motor
Vehicles, A dm inistration Services. May (1968).
7. New R esearch on the role of Alcohol and Drugs in Road Accidents,
Organisation for Economic Co-operation and Development, Paris (1978).
485
F ig u re 1
DETECTION OF ACIDIC & NEUTRAL DRUGS
TLC GC-AFID
BARBITURATES METHAQUALONE UREIDES CHLORMETHIAZOLEANTICONVULSANTS ULNZUD1AZCPINE (OVERDOSES) ANALGESIC/ANTIPYRETICS
F igu re 2
DETECTION OF BASIC DRUGS
TLC GC-AFIDZONAL SCREEN ON OV-17SCREEN 3 ISOTHERMAL TEMPS
DATA AVAILABLE FOR OVER 200 DRUGS. NARCOTIC ANALGESICS STIMULANTS ANTIDEPRESSANTS ANTIHISTAMINESPHENOTHIAZINES ANTIMALARIALSLOCAL ANAESTHETICS
486
DETECTION OF BENZODIAZEPINES (AS BENZO
PHENONES) AND MORPHINE
F igure 3
FIG
4:
SCHE
ME
FOR
SCRE
ENIN
G AC
IDIC
AN
} NE
UTRA
L DR
UGS
FIG
5:
SCHE
ME
FOR
BLOO
D BE
NZOD
IAZE
PINE
SC
REEN
ING
IN 8L
OCO
- BA
TCH
METH
OD
BATC
H M
ETH0
D
I CJ UJNi
O UJ X Z>co o r
UJ *— Xtr < <c cc cc a.D CD U CJ ►—«2 -I <C O < •-« CJ CJ O
a; uj —i uj o 2 o '-h 2 a. < to C x cn a x > uj m a ujUJ X O «—1 X
O C T • CJ2 <
t— CJ> - o UJu _ < 2*—ct: () <cot— < X< x cc UJCDUJ u_ X
488
r----
------
------
------
------
------
------
------
------
------
------
------
------
------
------
------
------
----1
-
EVAP
ORAT
E TO
MET
HYLA
TE
.
____
____
____
____
____
____
____
____
____
____
____
____
____
DR
YNES
Sc
CH„N
„
FIG
6 -
FREQ
UENC
Y OF
DETE
CTIO
N OF
DRUG
S IN
RTA
CASE
SCLLU
<!O
CL CL LU LU
O' QZ
LU
LU
LU
LU h- <LU 0£
a £2 XM
:s ^ < a m a 0 1-0_I ID _IX _J XO e> unN
o u*5
<x:orZD
CDcc<CD
COLDZDcnQo
<CL
<c
inCJcoLUCD—Icz<CJ
oCJcr:<
COLJ>
<QLUCO
M<C»—IOohsjzL JCOI
L J
<ccCDorcCDIZo
CD CJ
hslCJ
( 3
h- H-LJ z z2: <o CO to»—1 21 —J COo < ID LJ2: 1— > or»-H ? CO z Q_CD /l ►H o LJC ID X CJ Oz »—» »—Iz HH 1— 1— f—< H- z z 2CJ 00 < < <
O
CJLJLJQ
-O
-CDCM
-o
489
o
490
f ig u re 8
YEARLY TOTALS FOR DRUGS & DRIVING CASES ALCOHOL/DRUGS-DRIVING CASES, AND DRUGS POSSESSION CASES
491
t a b l e i
R. v. C. R. BROWNE
DEFENDANT ADMITTED:
FOUND ON ANALYSIS:
URINE
AMYLOBARBITONE
QUIN ALB ARBIT ONE
(PLUS HYDROXY METABOLITES)
AMPHETAMINE
METHYL AMPHETAMINE
EPHEDRINE
PROCAINE
METHADONE (PLUS METABOLITE)
MORPHINE
ASPIRIN
GOLD INJECTION
INDOMETHACIN
METHADONE
BLOOD
ZERO ALCOHOL
AMYLOBARBITONE (1.1 y g/ML)
QUINALBARBITONE (NOT MEASURABLE: Me-TBTH INTERFERED)
MORPHINE RIA POSITIVE ( 28 NG/ML)
(SAMPLE EXHAUSTED)
TABLE 2 : _RTA DRUGS CASES 1978 (January to September)
CASES INVOLVING "REGISTERED" 9.5%OR "SELF-CONFESSED" DRUGADDICTS
CASES INVOLVING "KNOWN" DRUG 15.5%ABUSERS
CASES IN WHICH THE ANALYTICAL 11 %RESULTS INDICATE DRUG ABUSE
CASES WITH NORMAL THERAPEUTIC 11 %BLOOD CONCENTRATION OF DRUG PLUS BELOW-THE-LIMIT ALCOHOL