1 of 16

IMPROVING AND UNDERSTANDING �POLY-DRUG INFORMATION

Max Roberts, PhD

Research Associate, Washington Traffic Safety Commission

WTSC Quarterly Meeting

October 20, 2022

2 of 16

WHAT IS A POLY-DRUG POSITIVE DRIVER?

  1. A driver that is positive for alcohol and one or more other drugs as confirmed by toxicology testing
    • Example: Alcohol + THC
  2. A driver that is positive for two or more drugs that are not alcohol as confirmed by toxicology testing
    • Example: THC + methamphetamine

2

3 of 16

DRUG AND/OR ALCOHOL POSITIVE DRIVERS INVOLVED IN A FATAL CRASH

​

​

​

​

​

​

​

​

​

​

  • ‘Poly-Drug’ and ‘Alcohol Only’ includes any alcohol greater than a BAC of zero

​

3

4 of 16

SCENARIO

Photo Credit: Nandu Vasudeval, Pexels.com

4

5 of 16

IDENTIFYING POTENTIAL FOR IMPAIRMENT

  • Impairing
    • Clear evidence and understanding of drugs ability to impair driving abilities
    • Methamphetamine, benzodiazepines, THC, zolpidem (Ambien)
  • Potentially impairing
    • Evidence may be mixed, but the potential for the drug to impair driving abilities exists
    • SSRI antidepressants, antihistamines, pseudoephedrine
  • Non-impairing
    • Drugs do not have serious impairing effects on driving ability
    • Caffeine, acetaminophen, non-active metabolites

​

​

5

6 of 16

SCREENING OUT DRUGS UNDER CERTAIN CONDITIONS

  • Non-impairing drugs removed (n=14)
    • Acetaminophen, benzene, caffeine, carboxyhemoglobin, glucose, ibuprofen, ketones, naloxone, nicotine/cotinine, quinine, salicylate, theobromine, trimethoprim, yohimbine
  • Non-impairing, non-active metabolites removed if they are alone with no parent drug present (n=4)
    • Benzoylecgonine, carboxy-THC, ecgonine methyl ester, norfentanyl
  • Non-impairing pharmaceuticals removed if alcohol is not present (n=13)
    • Dextromorphan, diltiazem, glipizide, metformin, nifedipine, pseudoephedrine, norpseudoephedrine, risperidone, 9-hydroxyrisperidone, warfarin

​

6

7 of 16

MATCHING PARENT DRUGS WITH METABOLITES

  • If ‘THC’ and ‘carboxy- THC’ are present, this should not be treated as two separate impairing drugs, but rather a single drug that has been/is being metabolized, ‘THC /carboxy- THC’
  • 39 parent-metabolite combinations formed

​

7

8 of 16

PARENT-METABOLITE COMPOUNDS

8

9 of 16

SCREENING VS. CONFIRMATORY RESULTS

  • Six different screening results periodically appeared in toxicology reports

​

9

10 of 16

SCREENING VS. CONFIRMATORY RESULTS

  • Removing screening results when confirmatory results are present

​

​

​

​

​

10

11 of 16

DRUG-POSITIVE DRIVER DATA*

BEFORE

  • All drivers involved in a fatal crash with a positive toxicology drug results (n=1,193)
  • 125 Total unique drugs
  • 373 Distinct combinations of drug

AFTER

  • All drivers involved in a fatal crash with a positive toxicology drug results (n=1,101)
    • 92 drivers removed
  • 106 Total unique drugs
  • 363 Distinct combinations of drug

​

11

  • Toxicology drug abstracts linked with traffic fatality data for drivers in fatal crashes from 2015 – 2020 (6 years)

*Excluding alcohol

​

12 of 16

CHANGE IN NUMBER OF DRUGS AMONG DRIVERS*

12

BEFORE

AFTER

*Excluding alcohol

​

13 of 16

COMBINING DRUGS AND ALCOHOL*

  • Drivers positive for alcohol and/or drugs
    • n=1,534
    • 433 positive for alcohol only
  • Majority, alcohol only (28%)
  • Followed by alcohol and THC/carboxy-THC (11%)

​

13

*Any BAC greater than zero

​

14 of 16

DRUG AND/ OR ALCOHOL POSITIVE DRIVERS INVOLVED IN A FATAL CRASH

14

BEFORE

15 of 16

DRUG AND/ OR ALCOHOL POSITIVE DRIVERS INVOLVED IN A FATAL CRASH

15

AFTER

16 of 16

Max Robert, PhD, Research Associate�mroberts@wtsc.wa.gov�Washington Traffic Safety Commission

16

Thank You