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DRUGGED DRIVINGDR MORRIS ODELLVICTORIAN INSTITUTE OF FORENSIC MEDICINE
DRUGGED DRIVING – THE ISSUES
• Legislative approaches
• Research methodology
• Prevalence
• Detection
• Impairment
• “Differential diagnosis”
• Prescribed drugs
• Specific Drugs
DRIVING – AN UNNATURAL ACT
• High speed decision making• Vision, Reaction time, cognition, all at
limits of capability• Physical demands of the task• Doing several things at once – divided
attention• Injury risk is high• Greatest non-homicide cause of
unnatural death
LEGISLATIVE APPROACHES
DUI – loosely defined prohibition of driving under the influence. Problems obtaining proof of intoxication
“Per se” laws – similar to 0.05% alcohol law –strict liability based on toxicology tests eg: saliva testing
DWI - Impairment based assessment – refinement of DUI to systematize observations (+/- toxicology)
RESEARCH INTO DRUGS & DRIVING
Laboratory studiesStandard psychomotor testsDriving simulatorsProblems – doses not realisticCannot realistically determine crash risk Epidemiological studiesRequire huge sample sizeNeed to control for vast number of drugs & combinations
data from fatalities vs. data from live drivers
PREVALENCE OF DRUGS ON ROADS
Very Difficult to determine
Injury study SA 2000 Alcohol 8.6%, THC 7.1%, Alc + THC 3%
Alfred Hospital study 2001-2 THC 39%, BZD 16%, Stim 12%, Opioid 7%
Vic Police DWI cases VIFM 2000-2 BZD 64%, Op 43%, THC 30%, Stim 13%, Alc 3%
Victorian Oral Fluid testing program 2005-10 Overall prevalence 2-3% BUT only 3 drugs and highly
targeted testing
APPREHENSION BY POLICE –SOURCE OF BIASScreening eg: Booze buses
On road behaviour
“Dob ins” from the Public
Breath tests to exclude alcohol
Roadside observations of impairment
Systematic method for recording observations
ASSESSMENT OF IMPAIRMENT
Observations InterviewPhysical signs eg: pupils, nystagmus, pulse, BP
Psychomotor tests eg: walk & turn, one leg stand
ToxicologyUrine, blood, saliva, otherQualitative vs. quantitative
POTENTIAL PROBLEMS
Serious medical conditions requiring attention
Non-serious conditions affecting assessment
Impairment due to illness being treated
Technical problems with examination
Drug effect worn off by time of exam
Conflicting effects of different drugs
OTHER CAUSES OF IMPAIRMENT
Medical conditions long standingacute or emergencies
Disabilities and/or deformities
Side effects of legitimately prescribed drugs
Psychiatric conditions
Acute stress - “pseudo impairment”
ACUTE ANXIETY - PANIC
May be triggered by distress of apprehension
Similarities to amphetamine effect
Can co-exist with drug effect
Release of adrenaline - “fight or flight”tremorsweatydilated pupils
SERIOUS MEDICAL CONDITIONS
Head injury
Internal injuries with haemorrhage
Over-dosage & severe intoxication
Epilepsy & post ictal states
Hypoglycaemia
Should be obvious on observation and interview
CHRONIC MEDICAL CONDITIONS
Neurological problemsold strokesdegenerative diseases - MS, Parkinson’s, Huntington’s
Eye problems licensing criteria allow one eyed drivers etc
Physical disabilitiesdeformitiesgait disorders
PRESCRIPTION DRUGS
Vast number capable of affecting drivingIn practice they are rarely a problem if
used properlyMedical & pharmacy adviceCompliance with dosesAllow time to develop toleranceMay be a valid defence to chargesEffects of condition being treated
DRUGGED DRIVING TOXICOLOGY
Specimen – blood vs. urine vs. saliva
Specified in relevant lawsPracticalitiesTimingEffect of delay on drug levels“readbacks” not usually possibleInterpretationCutoff levels for qualitative testsCorrelation of levels with doses/effects !!!!!
URINE TESTS- PRACTICAL PROBLEMS
LEGAL DRUGS
Enormous number of substances in legal use
OTCPrescribed
“Therapeutic” - used in treatment
Condition being treated may cause problems
“Use” and “Abuse”
SPECIFIC DRUGS
Tobacco & Alcohol
Cannabis
Amphetamines (Cocaine)
Opioids
Benzodiazepines
Other prescribed drugs
Others
CANNABIS
Product of Cannabis sativamarijuanahash(ish)mullgrassdopeetc
Physical increased heart rate
red eyespupils dilateddry mouthbalance
Nervous systemEuphoriaDisorientationAltered perceptionRelaxationSlowing of time perception
Hunger
EFFECTS OF CANNABIS
CANNABIS TOXICOLOGY
Active component is delta-9 THC
Short redistribution time 1-4 hours.
Thiopentone-like pharmacokinetics
Peak effect about 30 minutes
Long elimination half life - weeks
Metabolite is carboxy-THC
Long elimination half-life - days/weeks
TESTS FOR CANNABIS
Urine - “cannabinoids” - mostly metabolites
Positive up to 1-2 weeksBlood – snapshot of THC at the time of
collectionSaliva – short window of detection likely to
correlate with clinical effectsPost mortem – extremely variable – THC
levels may change in either direction after death
INTERPRETATION OF THC LEVELS
Unusual to get specimens during the peak
Baseline levels due to slow elimination - up to 5 ng/ml (cf 0.05% = 500,000ng/ml)
What is a realistic baseline in Australia in 2012?
Levels above baseline - are they evidence of impairment and if so how much?
Review - 11 ng/ml ~0.073% alcohol – is this realistic?
PRESCRIPTION DRUGS - OPIOIDS (NARCOTICS)
One of the oldest known groups of drugs (4000 BC)
Great number of different derivatives
Widespread medical and illegal use
Physical effectspinpoint pupilsrespiratory depression
constipationnausea/vomitingflushingcough suppression
Nervous effectsrelaxationsedation, comapain reliefeuphoriamental cloudingreduced aggressionreduced libido
EFFECTS OF NARCOTICS
OPIATES - SIGNS OF INTOXICATION
Interview & ObservationDrowsy - “on the nod”Needle tracksRouseable but falls asleep rapidlyDroopy eyelidsPinpoint pupilsSlow speech
WithdrawalNasty but rarely fatal
PRESCRIBED OPIATES
Very commonly found in combination with other sedating drugs
Codeine, tramadol alone – not associated with impairment (Bachs 2009)
Methadone, buprenorphine – not impairing if tolerance established and used as directed (Lenne 2003, Bernard 2010)
Methadone, buprenorphine – associated with increased crash risk due to “risky behaviour” (Corsenac 2011)
BENZODIAZEPINES“Minor tranquillizers”
Widely available
Widely used
Widely abused
Many types all with similar properties
Classic CNS depressants
BENZODIAZEPINES
Many types differ in duration of action
Times range from hours to daysDiazepam (Valium) Temazepam (Normison)Oxazepam (Serepax)Flunitrazepam (Rohypnol)Clonazepam (Rivotril)Alprazolam (Xanax)Midazolam (Hypnovel) - liquid form
PHARMACOLOGY OF BENZODIAZEPINES
Complex metabolism
Converted to other benzos in the body
Long lived products
Metabolic products may interact with other drugs after original drug effect has worn off
EFFECTS OF BENZODIAZEPINES
Interview & ObservationDrowsiness, “Drunk”, Slurred speechParadoxical excitement
“Taking off the brakes”
Clinical signsnystagmus the classic indicatorpupils not usually affected Incoordination
BENZODIAZEPINES AND DRIVING
The one drug group consistently found to affect driving & crash risk
BUT
Very few studies differentiate between prescribed and excessive dosing
Increased risk with long acting prescribed benzos in first few weeks of treatment (Smink 2010, Dubois 2008)
Different situation to excessive use of short acting benzos
Enormous potential to interact with other sedatives especially opiates
ANTIDEPRESSANTS
3 main groupings SSRI tricyclics MAO inhibitors
Common in community
Often in combination with other drugs
Modern SSRIs rarely cause impairment
Rarely abused except in suicide attempts
ANTIDEPRESSANTS - EFFECTS
Early effectssedationcholinergicCardiotoxicity with older types
Effects of depressionpsychomotor retardation
Interactions - alcohol, other drugs, serotonin syndrome
? Mania
OTHER DRUGS
Infinite number of drugs and combinations of drugs
OTC drugs
Rarely a problem with prescribed drugs
Rave scene
IV anaesthetics
Need to consider the reason why they were prescribed
Drugs in combination
THE END!