1.1 In
the light of the serious consequences for the individual,
and liabilities which can be incurred in the event
of a positive or incorrect test result, Simpson et
al discussed the need for established procedures covering
storage, chain of custody, confirmation of results
and appropriate legal standards for "library"
matching of spectra from unknown substances (e.g.
designer drugs) requiring identification.
1.2 Most
blood and urine tests for the presence of heroin differ
from alcohol test results as these measure a metabolite
of heroin (morphine) which is itself active. Heroin
is metabolised to 6-monoacetyl morphine and then to
morphine in the blood. Alcohol produces clear dose-related
impairment as measured by breath, blood or urine tests.
The presence of morphine in urine merely signifies
that the person had used or been exposed to opiates
at some point prior to the test.
1.3 Four
British police forces tested sweat or saliva testing
devices in early 1998, however in December 1998 the
DETR stated that "the operating
mechanisms in both deviced sometimes failed or proved
unreliable, and the notation by police of positive
or negative readings from the devices simply cannot
be regarded as meaningful. We cannot therefore use
the data in any way that could be construed as indicative
of drug use among drivers and it would be irresponsible
if we were to attempt to do so"
and conceded that "the incidence of drugs
in road accident casualties...does not give us any
help with accident causation". Niedbala
et al found "93.6% agreement
between oral fluid and urine" when
testing for opiates, and concluded "oral
fluid may be a reliable matrix for opiate detection".
Gjerde et al found that morphine levels in blood to
have resulted from metabolism of codeine and/or ethylmorphine,
stressing the importance of analysing body fluids
for a spectrum of opiate drugs where these are suspected
to have caused impairment.
1.4 Urine
screening is the most common method of detecting use
of cocaine and other drugs. Following collection,
samples are subjected to a chemical or immunological
screening test, involving a colour change on a dipstick,
with positive samples confirmed by GCMS or similar
analytical methods.
1.5 Hair
testing studies have claimed that morphine can be
detectable for over 6 months, but hair analysis if
further complicated by the variability in growth rates
and the tendency for the hair of afro-caribbean or
other dark haired ethnic groups to bind more effectively
to certain drugs, compared to caucasians. Piekoszewski
et al, studying opiates in hair, saliva and blood
serum, concluded: "From the clinical
toxicology point of view, hair analysis is supplementary
to urine, serum or saliva determination, but in drug
testing at the workplace it can play a crucial role."
Tagliaro et al concluded that "analytical
and interpretative problems still remain and these
limit the acceptance of this methodology, especially
when the results from hair analysis".
1.6 Huestis
et al reported sweat patches to provide positive results
for morphine in addicted persons, but concluded "the
percentage of false-negative results, at least in
this treatment population, indicates that weekly sweat
testing may be less sensitive than thrice weekly urine
testing in detecting opiate use.".
1.7 Saliva
testing is unlikely to become the preferred substrate
for determining opiate intoxication or recent use,
Samyn et al. reported "Recent
heroin abuse (n = 5) could be demonstrated to some
extent with Drugwipe on samples from the tongue but
only the two subjects with the highest saliva concentrations
of MAM (> 500 ng/ml) and morphine (> 500 ng/ml)
were positive." Furthermore results
can be influenced by the sampling methodology, Kato
et al reported that stimulation of saliva (by sour
candy) decreased the levels of cocaine and metabolites
compared to unstimulated saliva, attributed to lower
buccal pH in the stimulated condition.
2 Passive
Exposure & False Positives
2.1 Passive
inhalation of smoked cocaine and cannabis can produce
positive test results, Although I am unaware of studies
of passive exposure to smoked heroin, it is entirely
possible that false-positives could also result from
a person being in the same room or car as a heroin
smoker.
2.2 Morphine
can also be produced by other opiates, including those
in prescribed and over the counter pain-relief preparations.
Gjerde et al found that morphine levels in blood to
have resulted from metabolism of codeine and/or ethylmorphine,
stressing the importance of analysing body fluids
for a spectrum of opiate drugs where these are suspected
to have caused impairment. Monoacetylmorphine has
been proposed as a urinary marker for recent heroin
use.
2.3 Meneely
found that ingestion of poppy-seeds (25g) in cakes
generated opiate-positive urine tests (300 ng/ml cutoff
levels), although "no subjects
were found to exhibit symptoms of opiate impairment."
In the USA, workplace testing cut-off levels for morphine
were increased from 300ng/ml to 2000ng/ml in November
1998, to avoid false positives arising from medicinal
codeine preparations and poppy-seed foodstuffs. By
contrast, the legal limit of plasma morphine for driving
under Belgian law is 20ng/ml, equivalent to 10ng/ml
in blood, levels of 500ng/ml were found in saliva.
3 Opiate
Pharmacokinetics
3.1 Pharmacokinetics
is the study of the time course of how drugs are distributed
in the body, how long the effects last and how such
effects relate to drug tests.
3.2 Vandevenne
et al, reviewing detection times, reported "Experimental
data for total morphine using a cut-off of 300 ng/mL
suggest a detection time of 1 to 1.5 days for relatively
low doses of heroin (3-12 mg) administered via i.v.,
IN or i.m. route." Cone et al found
heroin levels in the blood to peak at 5 minutes after
nasal spray or intramuscular injection, identifying
the need to monitor blood levels of "heroin,
6-acetylmorphine, and morphine"
3.3 Smith
et al investigated the reliability of increased immunoassay
cut-off levels in detecting known doses of morphine
- 8 subject received intravenous doses of 3, 6, and
12 mg heroin HCl and four smoked 3.5-, 5.2-, 10.5-,
or 13.9-mg doses of heroin (base) - and eliminating
false positives, finding "Detection
times for morphine using the 300-ng/mL cutoff assays
was approximately 12 h for low dose and 24 to 48 h
for higher doses of heroin. For the two 2000-ng/mL
cutoff concentration assays detection time was about
12 h."
3.4 Dihydrocodeine
can be detected in urine for up to 4 days. As codeine
and other opiates require much larger doses than heroin
for their effects, they are likely to remain detectable
for longer periods.
