CFC Toxicology & Drug Analysis 4 — Questions and Answers
Question 1: A decedent is found with cherry-red lividity. In addition to carbon monoxide, which other toxicant can produce this postmortem finding?
- Arsenic
- Cyanide (Correct answer)
- Lead
- Organophosphates
Correct answer: Cyanide
Cyanide inhibits cytochrome c oxidase, preventing oxygen utilization and leaving blood fully oxygenated, producing cherry-red lividity similar to CO poisoning.
Question 2: In liquid chromatography-tandem mass spectrometry (LC-MS/MS), the term 'multiple reaction monitoring' (MRM) refers to:
- Screening for multiple drugs in a single injection without confirmation
- Monitoring precursor-to-product ion transitions for quantitative drug confirmation (Correct answer)
- Running replicate analyses to reduce measurement uncertainty
- Simultaneously screening immunoassay and chromatographic methods
Correct answer: Monitoring precursor-to-product ion transitions for quantitative drug confirmation
MRM monitors specific precursor ion to product ion transitions, providing high selectivity and sensitivity for quantitative confirmation of drugs in biological matrices.
Question 3: Which organ is the primary site of drug metabolism in the body?
- Kidney
- Lung
- Liver (Correct answer)
- Intestine
Correct answer: Liver
The liver is the primary organ of drug metabolism, containing high concentrations of cytochrome P450 enzymes responsible for phase I biotransformation.
Question 4: A forensic case involves suspected poisoning with organophosphate pesticide. Which biomarker is most useful for confirming acute exposure?
- Blood urea nitrogen (BUN)
- Serum cholinesterase activity (Correct answer)
- Serum creatinine
- Plasma albumin level
Correct answer: Serum cholinesterase activity
Organophosphates irreversibly inhibit acetylcholinesterase; depressed serum (pseudo)cholinesterase activity confirms acute organophosphate exposure.
Question 5: Which schedule classification under the U.S. Controlled Substances Act applies to drugs with no currently accepted medical use and high abuse potential?
- Schedule II
- Schedule III
- Schedule I (Correct answer)
- Schedule IV
Correct answer: Schedule I
Schedule I substances (e.g., heroin, LSD, marijuana federally) have no accepted medical use, a high potential for abuse, and a lack of accepted safety for use under medical supervision.
Question 6: In forensic toxicology, 'matrix effects' in mass spectrometry refer to:
- Interference from endogenous biological compounds affecting ionization efficiency (Correct answer)
- Temperature effects on column separation
- Degradation of analyte during long-term storage
- Cross-contamination between samples in an analytical batch
Correct answer: Interference from endogenous biological compounds affecting ionization efficiency
Matrix effects occur when co-extracted endogenous compounds (salts, phospholipids) suppress or enhance ionization of the target analyte, affecting quantitative accuracy.
Question 7: A urine specimen tests positive on immunoassay for benzodiazepines. Which drug would NOT be detected by most standard benzodiazepine immunoassays due to structural differences?
- Diazepam
- Lorazepam
- Alprazolam
- Clonazepam (Correct answer)
Correct answer: Clonazepam
Clonazepam is a nitrobenzodiazepine that is poorly detected by many standard immunoassays calibrated to oxazepam, often requiring specific LC-MS/MS confirmation.
CFC Toxicology & Drug Analysis 4
A decedent is found with cherry-red lividity.
In addition to carbon monoxide, which other toxicant can produce this postmortem finding?