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Opiates and Driving Ability
1 Overview
1.1 Heroin
(diamorphine) is a narcotic analgesic drug, one
of a family of opiate drugs which also includes
morphine, codeine and pharmaceutical products such
as dextropropoxyphene and dihydrocodeine. All these
drugs act on the same neurochemical system, relieving
pain, or the distress caused by pain, and relieving
stress so the user leaves behind his or her cares
and worries.
1.2 The
effects of heroin can last for 2-6 hours, depending
on dosage and the tolerance of the individual user.
The effects of a recreational dose include an initial
"rush" (effect of diamorphine proper),
followed by a feeling described as being wrapped
in cotton wool (once heroin is metabolised into
morphine). Addicts will feel an initial sense of
relief or release, but with tolerance and physical
dependence, the drug simply helps them feel normal,
rather than intoxicated.
1.3 Drug
interactions: Opiates interact with alcohol
to increase the depressive effects on respiration
and mood. Cannabis can potentiate the analgesic
effect of opiates.
1.4 The
effects of drugs on driving have been studied using
laboratory tests of psychomotor performance and
cognitive function, simulator studies, and assessment
of road accidents and driving records. IDMU is currently
engaged in research
2. Laboratory
Studies of Psychomotor & Cognitive Function
2.1 In
a study of cancer patients, Vainio et al found no
significant effect of morphine on "...intelligence,
vigilance, concentration, fluency of motor reactions,
or division of attention. Of the neural function
tests, reaction times (auditory, visual, associative),
thermal discrimination, and body sway with eyes
open were similar in the two groups; only balancing
ability with closed eyes was worse in the morphine
group. These results indicate that, in cancer patients
receiving long-term morphine treatment with stable
doses, morphine has only a slight and selective
effect on functions related to driving."
2.2 Pickworth
et al found hydromorphone to have no effect on circular
lights, digit symbol substitution, and serial math
tasks or card-sorting tasks. Oxycodone, a mu-opioid
receptor agonist, was found to cause "increased
reaction time and impaired vigilance, attention,
body balance and coordination of extraocular muscles".
2.3 Hill
& Zacny reported "Psychomotor
impairment was ... and absent with morphine (which)...
produced dose-dependent decreases in pupil size.."
In an earlier study, Zacny et al found "morphine
had no effect on psychomotor functioning."
in healthy non-using volunteers.
2.4 Sjogren
et al, studying patients receiving high-dose morphine
therapy, found "Vigilance/attention,
psychomotor speed, and working memory were significantly
impaired in chronic nonmalignant pain patients."
In a study of cognitive and psychomotor function,
O"Neill et al reported: "Morphine
had one major effect, which was to increase the
accuracy of responding on the choice reaction time
task, at every assessment. Morphine produced some
sporadic effects in other tests and an increase
in subjective calmness. These data show that oral
morphine may enhance performance in some measures
of cognitive function", in an earlier
study of cancer pain management O"Neill had
reported "opioids do have effects
on cognitive and psychomotor function, and although
many of these effects diminish once the patient
is on a stable dose... the relationship between
measurable effects and the performance of everyday
tasks such as driving is unclear."
2.5 Walker
et al found morphine and codeine "...did
not affect performance on Maddox-Wing, digit-symbol
substitution, coordination, auditory reaction, reasoning,
and memory tests. Dose-related decreases in pupil
size (miosis) were observed following codeine and
morphine. ...These results suggest that oral codeine
and morphine ... have only modest effects on mood,
produce few side effects, and do not impair performance."
Zacny et al found "morphine
produced minimal psychomotor impairment.",
and that "morphine "...did
not affect performance on the Digit Symbol Substitution
Test." However by contrast Petry
at al found "Morphine produced
significant dose-dependent effects in DSST performance...
and pupil diameter."
in occasional drug users, whereas Zacny et al, studying
healthy non-using volunteers, concluded "Some
aspects of psychomotor performance (reaction time,
Digit Symbol Substitution Test and Maddox Wing)
were impaired by morphine; however, eye-hand coordination
was not. Miosis was induced by morphine. Most effects
of morphine were dose-related, some effects peaked
soon after morphine injection (e.g., increased stimulated
and high ratings) and dissipated gradually, whereas
other effects did not peak until later into the
session (sedation or exophoria). Our results are
fairly consistent with other studies examining morphine
effects in healthy volunteers, and also indicate
that the profile of morphine effects differ between
healthy volunteers and those with a history of opiate
dependence."
2.6 Hanks
et al, studying healthy volunteers, found "morphine
produced significant impairment at 1 hour on tests
of secondary memory retrieval (delayed word recall
and picture recognition sensitivity). CFFT was reduced
for the whole observation period (6 h) achieving
statistical significance at 4 hours. Morphine 15
mg produced a significant improvement in accuracy
on the choice reaction time test at the 2, 4 and
6 h assessments. These results show minimal impairment
of cognitive and psychomotor function after single
oral doses of morphine and with possible improvement
in one test." However, also with
healthy volunteers, Kerr et al reported "morphine...
caused significant impairments of some but not all
elements of cognitive and motor function. The time
needed to encode and process serially presented
verbal information increased and the ability to
maintain low consistent levels of force decreased
during the morphine infusion. We also assessed verbal
recall 3 hours after the morphine and saline infusions.
Delayed recall of information presented during the
morphine infusion was significantly impaired. Our
results demonstrate that morphine can interfere
with cognitive and motor performance at plasma drug
concentrations within the usual therapeutic range."
In a general review of the effects of painkillers
on occupational health, Payne concluded "all
classes of analgesics may impair... neuropsychiatric
functioning, which may influence job performance
in specific instances."
2.7 Bourke
et al found "Morphine did not
impair psychomotor function (Trieger Dot Test (TDT)
and... Continuous Performance Test (CPT))"
Saddler at al compared the effects of alcohol and
morphine, finding "Ethanol
produced a significantly greater deterioration in
motor skills", with no effect of
morphine on reaction time.
2.8 Bradley
& Nicholson studied the effects of codeine on
visuo-motor coordination, dynamic visual acuity,
critical flicker fusion, digit symbol substitution,
complex reaction time and subjective mood. They
reported "The effect on visuo-motor
coordination was limited and was dose related and
linear, and performance was altered on visuo-motor
coordination with 60 and 90 mg codeine, and on dynamic
visual acuity with 90 mg codeine (P less than 0.05).
No other effect of codeine was detected."
Saarialho-Kere et al found "Codeine
... failed to affect performance in objective tests
(body sway, digit symbol substitution, flicker fusion,
Maddox wing, nystagmus) "
2.9 Conley
et al, studying the effect of cold-water immersion
on the effects of morphine among naive users found
"Morphine impaired psychomotor
performance during one of the warm-water immersions,
but not during the cold-water immersions."
In a comparison study of the cognitive effects of
morphine and hydromorphone, "morphine
had less adverse consequences",
Beauford et al found no significant effect of morphine
on psychological test scores.
2.10 Nasal
butorphanol in a high dose was found to "impair
psychomotor performance for up to 2 h, and produce
subjective effects for up to 3 h. The smaller dose
had no psychomotor-impairing effects, but had subjective
effects (including increased ratings of "sleepy").
All three active drug conditions included miosis
(pupil constriction)."
3 Cognitive
Function
3.1 Much
of the research involving the cognitive effects
of opiates has focussed on methadone maintenance
patients. Methadone has been found to adversely
affect cognitive ability, specifically memory impairment,
and also "information processing,
attention, short-term visual memory, delayed visual
memory, short-term verbal memory, long-term verbal
memory and problem solving."
3.2 Ornstein
et al.reported "heroin abusers
were impaired in learning the... intra-dimensional
shift component... tests of spatial working memory...
failed to show significant improvement between two
blocks of a sequence generation task after training
and additionally exhibited more perseverative behavior
on this task... profoundly... impaired on a test
of pattern recognition memory sensitive to temporal
lobe dysfunction.", and Eiber et
al noted "Opiate addicts showed
a decrease in episodic autobiographical memory but
an increase in semantic affective memory and objective
modalization."
3.3 Numerous
studies have investigated the effect of maternal
use during pregnancy on cognitive function of children,
mostly finding no effects once social circumstances
are controlled for, Goddard et al finding "childrens'
behaviour and cognitive skills were not adversely
affected", while Fabris et al found
"No long-term neurologic or
cognitive deficits are directly associated with
heroin or methadone use"
3.4 Castaneda
et al, studying patients with dual diagnosis of
psychiatric disorders and drug dependence, reported
"Heroin addicts reported that
heroin improved some of their psychiatric symptoms
and all of their cognitive dysfunctions."
Studying groups of individuals dependent on different
drugs and controls, Amir et al found heroin addicts
to make more errors in tests of cognitive impairment
than controls.
3.5 Various
studies have investigated cognitive impairment among
drug users infected with HIV, however few have attempted
to associate impairment with drug use whilst controlling
for HIV status, and most consider the effects to
be due to the virus rather than the drug. Del Pesce
et al found HIV infection was associated with cognitive
impairment in intravenous drug users compared to
seronegative users. Silberstein et al reported "seropositive
IVDAs may show evidence of impaired neuropsychological
function even in the absence of AIDS related symptoms
and are consistent with the hypothesis of the early
neurotropism of HTLV." Concha et
al, studying neuropsychological performance of drug
users, reported "Effects of
the frequency of reported past use of marijuana,
heroin, cocaine, barbiturates, and alcohol were
not statistically associated with performance on
the tests."
3.6 Cipolli
& Galliani, using Rorschachs ink blots, found
long-term heroin addicts to perform worse than addicts
of shorter duration, considering their results to
"support the hypothesis that
cognitive functioning is impaired along with addiction
time" Roszell et al, comparing patients
receiving antidepressants and methadone maintenance,
noted "There were no significant
differences between groups on cognitive measures."
Miller reported "A neuropsychological
review of systems is likely to show a pattern of
impairment in substance abusers that involves the
integration of different cognitive functions for
effective problem solving."
3.7 Keiser
et al found that a group of heroin addicts performed
better on the "positive Digit Span scatter"
test than neurotic/depressive patients, whilst Lombardo
et al found no differences in cognitive function
between low and medium-dose methadone patients.
However Gritz et al reported "Methadone
subjects performed significantly poorer on several
tests of learning and immediate recall compared
to abstinent subjects."
4 Driving
Performance
4.1 Meijler
considered the Dutch ban on driving for opiate addicts
to be unjustified: "There is
no scientific basis for such a measure, however.
On the contrary, current evidence indicates that
e.g. cancer patients using 209 mg morphine daily
for three months do not differ significantly from
a control group with respect to thinking abilities,
alertness, concentration, reaction speed and dividing
attention. For obvious reasons utmost care must
be observed with the use of morphine by traffic
participants. But a rigorous prohibition of driving
for patients requiring chronic alleviation of severe
pain needlessly restricts their mobility."
4.2 O"Neill
considered "the relationship
between measurable effects (of opiate drugs) and
the performance of everyday tasks such as driving
is unclear." Jonasson et al, studying
analgesic use among drivers suspected of driving
under the influence of drugs, concluded : "analgesics
containing dextropropoxyphene or codeine are not
drugs of primary interest in this specific population."
4.3 Heishman
et al studied the accuracy of field impairment tests,
finding that trained officers were able to identify
the correct class of drug in under one third of
test cases.
4.4 In
Denmark, Neilsen et al found "The
frequencies of accidents in cases with morphine
or methadon were lower than in the material as a
whole while the frequency of accidents for dextropropoxyphen
was higher". Smith, writing in the
British Medical Journal, considered that patients
taking stable dosages of morphine should be able
to drive safely. By contrast, Sticht et al described
two fatal traffic accidents following heroin consumption,
in one of which the concentration was such that
the driver was risking a fatal overdose.
4.5 Chesher,
reviewing the evidence in 1985, stated: "The
behavioural pharmacology of intravenously administered
heroin suggests that any drug induced deficit in
driving performance is not due to any effect on
psychomotor function, but might be expected from
the effect of the drug on mood states. Methadone,
as used in treatment schedules for narcotic dependence
produces no significant effect on measures of human
skills performance. Epidemiological data are contradictory
though the suggestion is that the involvement of
the narcotic analgesic drugs in road crashes is
unlikely to be a source of significant concern"
4.6 IDMU"s
1998 and 1999 drug user surveys found the overall
accident rate for the survey respondents as a whole
to be 0.608 per 100,000km (898 accidents in 147.8
million km), close to the national average. Frequency
of heroin use was assessed as experimental (less
than 10 times), occasional, regular, and daily.
The accident rate for all heroin users was lower
than the group as a whole at 0.507, although occasional
users showed a higher than average rate. A lower
proportion of regular or daily heroin users drove
than respondents as a whole.
Accident
rates among users of Heroin
Freq
No
Drivers
Mean
accids
Total
Number
Mean
km/ 5yrs
Total
km/5yrs
Total
accids
Accid.
Rate
%
users drive
Never
1835
0.44
2480
51994.16
128945517
807
0.626
74.0
Exp
156
0.38
203
53758.39
10912953
59
0.543
76.8
Occ
24
0.46
26
59261.54
1540800
11
0.717
92.3
Reg
13
0.46
22
47854.55
1052800
6
0.568
59.1
Daily
10
0.50
16
62000
992000
5
0.504
62.5
Ex-users
79
0.44
102
63670.46
6494387
35
0.535
77.5
Total
306
0.38
407
56352.19
22935341
116
0.507
75.2
4.7 The
study also asked respondents whether they had had
accidents under the influence of particular drugs.
Of 245 such accidents reported, only 5 involved
heroin. However because the low incidence of heroin
use, this suggested a slightly higher risk compared
to the incidence of use of other drugs, and did
not approach statistical significance.
4.8 In
the 1994 IDMU study, heavy polydrug use was associated
with a significantly higher level of accidents.
5 Culpability
analysis studies
5.1 Crouch
et al considered that in 50 out of 56 cases where
drugs or alcohol were found, these contributed to
the accident, however it is unclear to what extent
drugs other than alcohol were increased culpability.
5.2 An
Australian study of Drummer, investigated over 1000
accidents, using risk analysis to compare the relative
accident risks of alcohol, cannabis and other drugs,
finding alcohol (p
Opiates and Driving Ability
1 Overview
1.1 Heroin
(diamorphine) is a narcotic analgesic drug, one
of a family of opiate drugs which also includes
morphine, codeine and pharmaceutical products such
as dextropropoxyphene and dihydrocodeine. All these
drugs act on the same neurochemical system, relieving
pain, or the distress caused by pain, and relieving
stress so the user leaves behind his or her cares
and worries.
1.2 The
effects of heroin can last for 2-6 hours, depending
on dosage and the tolerance of the individual user.
The effects of a recreational dose include an initial
"rush" (effect of diamorphine proper),
followed by a feeling described as being wrapped
in cotton wool (once heroin is metabolised into
morphine). Addicts will feel an initial sense of
relief or release, but with tolerance and physical
dependence, the drug simply helps them feel normal,
rather than intoxicated.
1.3 Drug
interactions: Opiates interact with alcohol
to increase the depressive effects on respiration
and mood. Cannabis can potentiate the analgesic
effect of opiates.
1.4 The
effects of drugs on driving have been studied using
laboratory tests of psychomotor performance and
cognitive function, simulator studies, and assessment
of road accidents and driving records. IDMU is currently
engaged in research
2. Laboratory
Studies of Psychomotor & Cognitive Function
2.1 In
a study of cancer patients, Vainio et al found no
significant effect of morphine on "...intelligence,
vigilance, concentration, fluency of motor reactions,
or division of attention. Of the neural function
tests, reaction times (auditory, visual, associative),
thermal discrimination, and body sway with eyes
open were similar in the two groups; only balancing
ability with closed eyes was worse in the morphine
group. These results indicate that, in cancer patients
receiving long-term morphine treatment with stable
doses, morphine has only a slight and selective
effect on functions related to driving."
2.2 Pickworth
et al found hydromorphone to have no effect on circular
lights, digit symbol substitution, and serial math
tasks or card-sorting tasks. Oxycodone, a mu-opioid
receptor agonist, was found to cause "increased
reaction time and impaired vigilance, attention,
body balance and coordination of extraocular muscles".
2.3 Hill
& Zacny reported "Psychomotor
impairment was ... and absent with morphine (which)...
produced dose-dependent decreases in pupil size.."
In an earlier study, Zacny et al found "morphine
had no effect on psychomotor functioning."
in healthy non-using volunteers.
2.4 Sjogren
et al, studying patients receiving high-dose morphine
therapy, found "Vigilance/attention,
psychomotor speed, and working memory were significantly
impaired in chronic nonmalignant pain patients."
In a study of cognitive and psychomotor function,
O"Neill et al reported: "Morphine
had one major effect, which was to increase the
accuracy of responding on the choice reaction time
task, at every assessment. Morphine produced some
sporadic effects in other tests and an increase
in subjective calmness. These data show that oral
morphine may enhance performance in some measures
of cognitive function", in an earlier
study of cancer pain management O"Neill had
reported "opioids do have effects
on cognitive and psychomotor function, and although
many of these effects diminish once the patient
is on a stable dose... the relationship between
measurable effects and the performance of everyday
tasks such as driving is unclear."
2.5 Walker
et al found morphine and codeine "...did
not affect performance on Maddox-Wing, digit-symbol
substitution, coordination, auditory reaction, reasoning,
and memory tests. Dose-related decreases in pupil
size (miosis) were observed following codeine and
morphine. ...These results suggest that oral codeine
and morphine ... have only modest effects on mood,
produce few side effects, and do not impair performance."
Zacny et al found "morphine
produced minimal psychomotor impairment.",
and that "morphine "...did
not affect performance on the Digit Symbol Substitution
Test." However by contrast Petry
at al found "Morphine produced
significant dose-dependent effects in DSST performance...
and pupil diameter."
in occasional drug users, whereas Zacny et al, studying
healthy non-using volunteers, concluded "Some
aspects of psychomotor performance (reaction time,
Digit Symbol Substitution Test and Maddox Wing)
were impaired by morphine; however, eye-hand coordination
was not. Miosis was induced by morphine. Most effects
of morphine were dose-related, some effects peaked
soon after morphine injection (e.g., increased stimulated
and high ratings) and dissipated gradually, whereas
other effects did not peak until later into the
session (sedation or exophoria). Our results are
fairly consistent with other studies examining morphine
effects in healthy volunteers, and also indicate
that the profile of morphine effects differ between
healthy volunteers and those with a history of opiate
dependence."
2.6 Hanks
et al, studying healthy volunteers, found "morphine
produced significant impairment at 1 hour on tests
of secondary memory retrieval (delayed word recall
and picture recognition sensitivity). CFFT was reduced
for the whole observation period (6 h) achieving
statistical significance at 4 hours. Morphine 15
mg produced a significant improvement in accuracy
on the choice reaction time test at the 2, 4 and
6 h assessments. These results show minimal impairment
of cognitive and psychomotor function after single
oral doses of morphine and with possible improvement
in one test." However, also with
healthy volunteers, Kerr et al reported "morphine...
caused significant impairments of some but not all
elements of cognitive and motor function. The time
needed to encode and process serially presented
verbal information increased and the ability to
maintain low consistent levels of force decreased
during the morphine infusion. We also assessed verbal
recall 3 hours after the morphine and saline infusions.
Delayed recall of information presented during the
morphine infusion was significantly impaired. Our
results demonstrate that morphine can interfere
with cognitive and motor performance at plasma drug
concentrations within the usual therapeutic range."
In a general review of the effects of painkillers
on occupational health, Payne concluded "all
classes of analgesics may impair... neuropsychiatric
functioning, which may influence job performance
in specific instances."
2.7 Bourke
et al found "Morphine did not
impair psychomotor function (Trieger Dot Test (TDT)
and... Continuous Performance Test (CPT))"
Saddler at al compared the effects of alcohol and
morphine, finding "Ethanol
produced a significantly greater deterioration in
motor skills", with no effect of
morphine on reaction time.
2.8 Bradley
& Nicholson studied the effects of codeine on
visuo-motor coordination, dynamic visual acuity,
critical flicker fusion, digit symbol substitution,
complex reaction time and subjective mood. They
reported "The effect on visuo-motor
coordination was limited and was dose related and
linear, and performance was altered on visuo-motor
coordination with 60 and 90 mg codeine, and on dynamic
visual acuity with 90 mg codeine (P less than 0.05).
No other effect of codeine was detected."
Saarialho-Kere et al found "Codeine
... failed to affect performance in objective tests
(body sway, digit symbol substitution, flicker fusion,
Maddox wing, nystagmus) "
2.9 Conley
et al, studying the effect of cold-water immersion
on the effects of morphine among naive users found
"Morphine impaired psychomotor
performance during one of the warm-water immersions,
but not during the cold-water immersions."
In a comparison study of the cognitive effects of
morphine and hydromorphone, "morphine
had less adverse consequences",
Beauford et al found no significant effect of morphine
on psychological test scores.
2.10 Nasal
butorphanol in a high dose was found to "impair
psychomotor performance for up to 2 h, and produce
subjective effects for up to 3 h. The smaller dose
had no psychomotor-impairing effects, but had subjective
effects (including increased ratings of "sleepy").
All three active drug conditions included miosis
(pupil constriction)."
3 Cognitive
Function
3.1 Much
of the research involving the cognitive effects
of opiates has focussed on methadone maintenance
patients. Methadone has been found to adversely
affect cognitive ability, specifically memory impairment,
and also "information processing,
attention, short-term visual memory, delayed visual
memory, short-term verbal memory, long-term verbal
memory and problem solving."
3.2 Ornstein
et al.reported "heroin abusers
were impaired in learning the... intra-dimensional
shift component... tests of spatial working memory...
failed to show significant improvement between two
blocks of a sequence generation task after training
and additionally exhibited more perseverative behavior
on this task... profoundly... impaired on a test
of pattern recognition memory sensitive to temporal
lobe dysfunction.", and Eiber et
al noted "Opiate addicts showed
a decrease in episodic autobiographical memory but
an increase in semantic affective memory and objective
modalization."
3.3 Numerous
studies have investigated the effect of maternal
use during pregnancy on cognitive function of children,
mostly finding no effects once social circumstances
are controlled for, Goddard et al finding "childrens'
behaviour and cognitive skills were not adversely
affected", while Fabris et al found
"No long-term neurologic or
cognitive deficits are directly associated with
heroin or methadone use"
3.4 Castaneda
et al, studying patients with dual diagnosis of
psychiatric disorders and drug dependence, reported
"Heroin addicts reported that
heroin improved some of their psychiatric symptoms
and all of their cognitive dysfunctions."
Studying groups of individuals dependent on different
drugs and controls, Amir et al found heroin addicts
to make more errors in tests of cognitive impairment
than controls.
3.5 Various
studies have investigated cognitive impairment among
drug users infected with HIV, however few have attempted
to associate impairment with drug use whilst controlling
for HIV status, and most consider the effects to
be due to the virus rather than the drug. Del Pesce
et al found HIV infection was associated with cognitive
impairment in intravenous drug users compared to
seronegative users. Silberstein et al reported "seropositive
IVDAs may show evidence of impaired neuropsychological
function even in the absence of AIDS related symptoms
and are consistent with the hypothesis of the early
neurotropism of HTLV." Concha et
al, studying neuropsychological performance of drug
users, reported "Effects of
the frequency of reported past use of marijuana,
heroin, cocaine, barbiturates, and alcohol were
not statistically associated with performance on
the tests."
3.6 Cipolli
& Galliani, using Rorschachs ink blots, found
long-term heroin addicts to perform worse than addicts
of shorter duration, considering their results to
"support the hypothesis that
cognitive functioning is impaired along with addiction
time" Roszell et al, comparing patients
receiving antidepressants and methadone maintenance,
noted "There were no significant
differences between groups on cognitive measures."
Miller reported "A neuropsychological
review of systems is likely to show a pattern of
impairment in substance abusers that involves the
integration of different cognitive functions for
effective problem solving."
3.7 Keiser
et al found that a group of heroin addicts performed
better on the "positive Digit Span scatter"
test than neurotic/depressive patients, whilst Lombardo
et al found no differences in cognitive function
between low and medium-dose methadone patients.
However Gritz et al reported "Methadone
subjects performed significantly poorer on several
tests of learning and immediate recall compared
to abstinent subjects."
4 Driving
Performance
4.1 Meijler
considered the Dutch ban on driving for opiate addicts
to be unjustified: "There is
no scientific basis for such a measure, however.
On the contrary, current evidence indicates that
e.g. cancer patients using 209 mg morphine daily
for three months do not differ significantly from
a control group with respect to thinking abilities,
alertness, concentration, reaction speed and dividing
attention. For obvious reasons utmost care must
be observed with the use of morphine by traffic
participants. But a rigorous prohibition of driving
for patients requiring chronic alleviation of severe
pain needlessly restricts their mobility."
4.2 O"Neill
considered "the relationship
between measurable effects (of opiate drugs) and
the performance of everyday tasks such as driving
is unclear." Jonasson et al, studying
analgesic use among drivers suspected of driving
under the influence of drugs, concluded : "analgesics
containing dextropropoxyphene or codeine are not
drugs of primary interest in this specific population."
4.3 Heishman
et al studied the accuracy of field impairment tests,
finding that trained officers were able to identify
the correct class of drug in under one third of
test cases.
4.4 In
Denmark, Neilsen et al found "The
frequencies of accidents in cases with morphine
or methadon were lower than in the material as a
whole while the frequency of accidents for dextropropoxyphen
was higher". Smith, writing in the
British Medical Journal, considered that patients
taking stable dosages of morphine should be able
to drive safely. By contrast, Sticht et al described
two fatal traffic accidents following heroin consumption,
in one of which the concentration was such that
the driver was risking a fatal overdose.
4.5 Chesher,
reviewing the evidence in 1985, stated: "The
behavioural pharmacology of intravenously administered
heroin suggests that any drug induced deficit in
driving performance is not due to any effect on
psychomotor function, but might be expected from
the effect of the drug on mood states. Methadone,
as used in treatment schedules for narcotic dependence
produces no significant effect on measures of human
skills performance. Epidemiological data are contradictory
though the suggestion is that the involvement of
the narcotic analgesic drugs in road crashes is
unlikely to be a source of significant concern"
4.6 IDMU"s
1998 and 1999 drug user surveys found the overall
accident rate for the survey respondents as a whole
to be 0.608 per 100,000km (898 accidents in 147.8
million km), close to the national average. Frequency
of heroin use was assessed as experimental (less
than 10 times), occasional, regular, and daily.
The accident rate for all heroin users was lower
than the group as a whole at 0.507, although occasional
users showed a higher than average rate. A lower
proportion of regular or daily heroin users drove
than respondents as a whole.
Accident
rates among users of Heroin
Freq
No
Drivers
Mean
accids
Total
Number
Mean
km/ 5yrs
Total
km/5yrs
Total
accids
Accid.
Rate
%
users drive
Never
1835
0.44
2480
51994.16
128945517
807
0.626
74.0
Exp
156
0.38
203
53758.39
10912953
59
0.543
76.8
Occ
24
0.46
26
59261.54
1540800
11
0.717
92.3
Reg
13
0.46
22
47854.55
1052800
6
0.568
59.1
Daily
10
0.50
16
62000
992000
5
0.504
62.5
Ex-users
79
0.44
102
63670.46
6494387
35
0.535
77.5
Total
306
0.38
407
56352.19
22935341
116
0.507
75.2
4.7 The
study also asked respondents whether they had had
accidents under the influence of particular drugs.
Of 245 such accidents reported, only 5 involved
heroin. However because the low incidence of heroin
use, this suggested a slightly higher risk compared
to the incidence of use of other drugs, and did
not approach statistical significance.
4.8 In
the 1994 IDMU study, heavy polydrug use was associated
with a significantly higher level of accidents.
5 Culpability
analysis studies
5.1 Crouch
et al considered that in 50 out of 56 cases where
drugs or alcohol were found, these contributed to
the accident, however it is unclear to what extent
drugs other than alcohol were increased culpability.
5.2 An
Australian study of Drummer, investigated over 1000
accidents, using risk analysis to compare the relative
accident risks of alcohol, cannabis and other drugs,
finding alcohol (p
