Forensic Toxicology Exam 1 Flashcards
What is toxicology?
the study of the harmful effects of chemicals on living organisms
What is forensic toxicology?
the application of toxicology for the purposes of the law such as: human performance, forensic drug testing, postmortem purposes
Human Performance Toxicology
- The effect of licit and illicit drugs on skills, acquisition, learning and performance
- Uses “real life” tests and laboratory based psychomotor tests
- Development of field sobriety testing, DRE program and establishment of 0.08% BAC as DUI
Forensic Drug Testing
- Military: drug dependent individuals barred from service, referred to treatment, post-accident investigations.
- Criminal Justice System: post-accident or homicide investigations, monitoring prison populations with testing at time of arrest, prison term, probation, parole.
- Private Sector: pre-employment screening, for-cause testing, post-accident investigations, sports (human/animal), insurance industry.
What kind of samples can you obtain for drug testing?
- urine
- hair
- saliva
- sweat
- blood / serum
What are challenges to overcome with urine drug testing?
- Substitution
- Adulteration
- Dilution
testing scheme
- immunoassay in the screening process
- if positive, confirm via testing for specific product
Screening
- Rapid results
- Preliminary identification of drug or drug classes
- May not provide information on specific drug
- Does not provide amount of drug present
Confirmation
- Greater sensitivity and specificity
- Verifies identity and quantitate specific drug/metabolite
- More expensive than the screening test
- Mass spectroscopy
Challenges to immunoassay: negative results
- Test not sensitive to a specific drug
- Drug levels not high enough to be reported
- Drug not used in recent past
- Sample artificially diluted
- Substance(s) present that interfere with test
Challenges to immunoassay: positive results
- Positive result due to poor specificity
- Many cross-reacting substances
Challenges to immunoassay: amphetamines
- False positives with: ephedrine, pseudoephedrine, β-phenethylamine
- False negative may happen with ecstacy
Challenges to immunoassay: cocaine
- Positives with Coca-leaf tea (true positive)
- Lidocaine, benzocaine will not give false positive
Challenges to immunoassay: morphine
- False positives can happen with: Fluoroquinolones, Rifampin
- True positive with Poppy seed
- False negatives happen with all synthetic / most semisynthetic opioids (they have their own specific tests)
Postmorten Forensic Toxicology
To investigate cause and manner of death
- Drug intoxication / overdose cases
- Homicides
- Suicides
- Accidents
- Natural deaths
Postmortem Forensic Toxicology
To investigate cause and manner of death
- Drug intoxication / overdose cases
- Homicides
- Suicides
- Accidents
- Natural deaths
What are the types of specimens that can be obtained to test for postmortem forensic toxicology?
- Blood (Heart, femoral, subclavian)
- Vitreous
- Urine
- Bile (SIDS)
- Liver
- Brain
- Gastric
- Kidney
- Hair, Nails if needed
What is the specimen of choice when detecting, quantifying, and interpreting drug concentrations?
blood
What is the issue with postmortem redistribution into the heart blood?
- Protein-bound drug released from tissue, diffuses into blood
- Redistribution of serum concentration into heart blood
How do you minimize the issues with postmortem redistribution?
- draw specimens from at least two sites (central compartment and peripheral site)
Which location of blood collection is best for blood interpretation in postmortem redistribution?
femoral vein
Why isn’t the subclavian vein good for collecting a sample for postmortem interpretation?
also subject to redistribution for some drugs
How do you make sure you have an accurate blood specimen?
- add preservatives such as sodium fluoride to inhibit pseudocholinesterase and microorganism activity
- do a rapid analysis
- refrigerate sample
- alsoanalyze vitreous and/or urine to compare and/or confirm
