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!