British Medical Journal, Specialty Journals in
Medical News Today, 26 Dec 2006
One in three drivers suspected of driving while
‘over the limit’ but subsequently found to be below
maximum permissible levels of alcohol, nevertheless
tested positive for a range of drugs, reveals
research in Injury Prevention.
The findings prompt the authors to call for routine
drugs testing in all drivers who are suspected of
being over the limit for alcohol.
The researchers base their findings on 2000 blood
and urine specimens taken from drivers who had been
stopped by police on suspicion of driving while
‘under the influence’ over a period of two years in
Half of the specimens were below the maximum legal
alcohol limit of 80 mg/100 ml for blood and 107
mg/100 ml for urine. The other half were all above.
But when analysed further, one in three samples
below the legal limit, tested positive for a range
of drugs. These drivers were also more likely to be
taking a cocktail of drugs.
This rate was almost twice as high as that of
drivers over the legal limit, one in seven of whom
tested positive for drugs.
The drugs found included amphetamines,
metamphetamines, benzodiazepines, cannabis, cocaine,
opiates and the heroin substitute methadone. The
most commonly found drug was cannabis.
Rates of testing positive for drugs were marginally
higher among men than they were among women
Based on the samples in the study, the authors
calculate that almost 16% (one in six) of all
drivers stopped and tested under suspicion of
driving under the influence of an ‘intoxicant’ would
test positive for drugs.
As blood alcohol levels rose, the likelihood of
testing positive for drugs fell. But more than one
in 10 drivers at least 2.5 times over the legal
limit for blood alcohol (greater than 200 mg/100ml)
also tested positive for drugs.
And among those with minimal blood alcohol levels,
over two thirds tested positive for at least one
type of drug, the findings showed.
Being under the legal limit for alcohol, being
stopped in a city, stopped between 6 am and 4 pm or
between 4 pm and 9 pm, and being under 35 years were
all independently associated with drug taking.
Too little attention has been paid to the adverse
effects of drugs on driving, but drugged driving can
be as dangerous as drunken driving, say the authors.