Drug Impaired Driving

Transcription

1 Drug Impaired Driving Dwain C. Fuller, D-FTCB, TC-NRCC Technical Director of Toxicology, VANTHCS Private Practice Forensic Toxicology Consultant Traffic Safety Initiative Conference, Austin, Texas April 2014 Overview Types of Toxicology Human Performance Toxicology Laboratory Testing Interpretation Challenges Limitations New Drugs Forensic Toxicology Drugs and poisons in human biological specimens with legal implications. Three sub-disciplines: Forensic Urine Drug Testing Postmortem Forensic Toxicology Human Performance Toxicology

2 Forensic Toxicology Drugs and poisons in human biological specimens with legal implications. Three sub-disciplines: Forensic Urine Drug Testing Postmortem Forensic Toxicology Human Performance Toxicology Forensic Toxicology Drugs and poisons in human biological specimens with legal implications. Three sub-disciplines: Forensic Urine Drug Testing Postmortem Forensic Toxicology Human Performance Toxicology Forensic Toxicology Drugs and poisons in human biological specimens with legal implications. Three sub-disciplines: Forensic Urine Drug Testing Postmortem Forensic Toxicology Human Performance Toxicology

3 Human Performance Toxicology Effects of drugs on living humans Performance of what? Driving Walking Making judgments Drug Facilitated Sexual Assault Other The Role of the Toxicologist Testing Alcohol Drugs Other intoxicants Interpretation Substance Concentration Context Other factors Testimony Testing - Alcohol Usually dual column gas chromatography-flame ionizationheadspace Identifies analytes by differing retention times on two different chromatographic columns Well-established and specific Sometimes enzymatic analysis (hospital specimens) Doesn t directly measure ethanol Measures an enzyme/substrate/cofactor reaction May produce false or elevated results under certain conditions Rarely gas chromatography/mass spectrometry (GC/MS) Highly defensible Probably overkill

4 Testing - Drugs Two step process Screening Typically immunoassay Based on antibody-antigen reactions Non-specific Limited in scope Must meet threshold requirement Not forensically defensible without confirmation Confirmation/Quantitation Typically mass spectrometric (GC/MS, LC/MS, LC/MS/MS, etc.) Usually qualitative and quantitative for DUID Must meet LOD requirement Wide scope possible, but usually restricted to limited menu Labor intensive = time consuming = expensive Often different analytical scheme and analyses for different drugs Side Note: New Technologies The Dream! Side Note: New Technologies The Reality!

5 Alcohol vs. Drugs in Driving Alcohol The most prevalent drug Extremely well-studied and understood Reasonably dependable dose-response relationship Per se concentration Drugs Hundreds of potential drugs Prevalence not well-understood May be over or underestimated Less studied in a controlled fashion Dose-response relationships less understood and more diverse Proof of impairment usually required Challenges for the Toxicologist Combatting cum hoc ergo propter hoc logic. Understanding and appreciating literature biases. Drug impairment is often different to alcohol impairment. Motor skills Drowsiness Cognitive impairment Drugs with different phases of action. Tolerance Stimulant use and abuse How much is too much? (What equals 0.08 EtOH?) Polypharmacy and drug-alcohol interactions How can the report be negative? Forensic toxicology is not practiced in a vacuum! The Burden of Proof Impairment DRE/SFST/Observations

6 Driving Behavior Too fast Too slow Weaving At cause accident Hitting fixed object Hitting other vehicles or pedestrians Hit and run Failure to abide by traffic rules Traffic signs or signals Wrong way driving Stopped on road SFST and DRE SFST Standardized Field Sobriety Test HGN Horizontal Gaze Nystagmus WAT Walk and Turn OLS One Leg Stand DRE Drug Recognition Exam (or Expert) DRE examinations, as opposed to SFST, are best conducted under a controlled environment rather than roadside. HGN Horizontal Gaze Nystagmus VGN Vertical Gaze Nystagmus Lack of Convergence Pupil Size Reaction to Light Pulse Blood Pressure Temperature Muscle Tone DRE 12 Steps 1. Breath alcohol test Does alcohol account for the observed impairment? Usually no DRE eval if BAC> Interview of Arresting Officer 3. Preliminary Examination Eye examinations and subject is questioned for any evidence of medical complication 4. Eye Examination HGN VGN Lack of convergence Slide Courtesy of Laura Liddicoat, Wisconsin State Laboratory of Hygiene

7 DRE 12 Steps 5. Divided Attention Psychophysical Tests Romberg Balance Finger to Nose WAT OLS 6. Vital Signs Pulse (x3) Body temperature Blood Pressure 7. Dark Room Pupil size in room light, near total darkness, direct light 8. Muscle Tone Slide Courtesy of Laura Liddicoat, Wisconsin State Laboratory of Hygiene DRE 12 Steps 9. Examination for injection sites 10. Suspect s Statements / Other Observations 11. Opinion of Evaluator DRE documents conclusions and category(s) of drugs causing the impairment 12. Toxicological Examination Specimen for Toxicology testing is obtained and sent to laboratory for analysis Slide Courtesy of Laura Liddicoat, Wisconsin State Laboratory of Hygiene DRE Matrix

8 Pupils Horizontal Gaze Nystagmus Involuntary jerking of the eyes as angle of horizontal gaze increases Caused by alcohol and CNS depressants Angle of onset is related to BAC Copyright 2011, Dwain C. Fuller Which Drugs Can Impair Driving? Any drug that changes the way we perceive or react to the environment. (Perception, tracking, coordination, reaction time, attention, judgment, etc.) CNS depressants Multiple effects Cannabinoids Chiefly cognitive Stimulants Can enhance driving in some doses Risk-taking Exhaustion Opioids drowsiness

9 CNS Depressants HGN Confusion Sedation Drowsiness Droopy eyelids Slurred speech Poor balance Poor coordination Disorientation Memory loss Slowed reaction time Low blood pressure Slowed pulse Poor divided attention performance Benzodiazepines and Tolerance Benzodiazepines are CNS depressants with activity ranging from anesthetic induction to sleep enhancement to antianxiety. All benzodiazepines can impair driving. Not all drivers with benzodiazepines on board are necessarily impaired. Tolerance to the psychomotor and sedative effects of short half-life benzodiazepines can develop within a matter of days to a few weeks. Supra-therapeutic and acute doses of short half-life benzodiazepines are the most impairing. CNS Stimulants Improved reaction time Relief from fatigue Improved vigilance Increased risk taking Increased blood pressure Increased pulse Increased body temperature Agitation Hyperactivity Irritability Confusion Suspiciousness Paranoia Delusions Hallucination Violence Exhaustion Fatigue Hypersomnolence Depression

10 Stimulants Logan, BK. Journal of Forensic Sciences. 41(3) 1996, So does the number mean anything? Provides the toxicologist with a starting point. With some limitations, can be compared to normal therapeutic ranges. Should be interpreted with caution. Should never be interpreted without context. Toxicologist should understand the limitations of his/her interpretative paradigm. Naturalistic studies Controlled studies Naturalistic studies Studies often report the drug concentration of people who are stopped for poor driving, wrecks, or some other behavior that bring them in contact with law enforcement. This produces a selection bias toward those who are impaired by a substance, and omits, perhaps even a majority of, subjects who may be unimpaired at the same concentrations. These studies typically provide no information about how many people were stopped or came into contact with law enforcement for these same reasons in which no drugs were detected.

11 Naturalistic studies Controlled Studies The preferred studies are those which are placebo controlled and double blind. At times, actual driving performance (SDLP) Behavioral tests < Simulated driving < Actual driving Even at best, not real world Limitation on controlled studies Institutional Review Board Issues Ethics Safety Cost and Logistics Food Housing Compensation SDLP Standard Deviation of Lateral Position Verster JC, Roth T. Int J Gen Med. 2011; 4: Copyright Dwain C. Fuller 2012

12 So why not use per se concentrations? 18 states have some form of per se concentrations for commonly abused illicit drugs ranging from no tolerance to specific concentrations Pros Eases interpretative burden May discourage illicit drug use Cons Choosing the per se concentration Some drugs share metabolites with legitimate drugs Legal THC use Marinol Sativex Prescription medications? New Drugs Synthetic Cannabinoids Spice, K2, etc. Bath Salts Amphetamine analogs sold as bath salts, plant food, etc. Synthetic Cannabinoids Sold as incense or potpourri, Not for Human Consumption Most were developed for pharmaceutical research on the cannabinoid receptor Some are DEA scheduled Ever moving target

13 Bath Salts - Cathinones Widely varied synthetic stimulants and hallucinogens similar to amphetamine Based on cathinone or Khat Native to Africa Leaves chewed or made into tea Some are DEA scheduled Ever moving target Questions and Discussion

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