Toxicology & Drug Analysis Flashcards

Which specimen is most useful for determining drug exposure over a period of approximately 90 days?

Answer: Hair

Hair grows approximately 1 cm per month, and a 3 cm segment reflects roughly 90 days of drug exposure through incorporation during keratinization.

In forensic cases involving suspected opioid overdose, which endogenous substance must be distinguished from exogenous morphine in hair testing?

Answer: Heroin (diacetylmorphine)

The presence of 6-monoacetylmorphine (6-MAM), a unique heroin metabolite, distinguishes heroin use from endogenous morphine or poppy seed ingestion.

The Widmark formula is used in forensic toxicology primarily to:

Answer: Estimate blood alcohol concentration from ingested ethanol

The Widmark formula estimates BAC based on amount of alcohol consumed, body weight, and gender-based distribution factor (r).

Which synthetic opioid has an analgesic potency approximately 100 times that of morphine and is frequently encountered in forensic drug casework?

Answer: Fentanyl

Fentanyl is approximately 100 times more potent than morphine and is a leading cause of opioid overdose deaths in forensic casework.

A urine specimen submitted for drug testing has a creatinine of 2 mg/dL and specific gravity of 1.001. The appropriate forensic interpretation is:

Answer: The specimen is substituted or severely diluted

Creatinine below 2 mg/dL and specific gravity of 1.001 or less meet federal criteria for a substituted specimen, indicating it is not consistent with normal human urine.

Which class of drugs is detected by the EMIT immunoassay using a phencyclidine (PCP) antibody but may also cross-react with dextromethorphan?

Answer: Dissociative anesthetics

Both PCP and dextromethorphan are NMDA receptor antagonists (dissociative agents), sharing enough structural similarity to cause cross-reactivity in PCP immunoassays.

What does the term 'chain of custody' ensure in forensic toxicology sample handling?

Answer: Sample integrity and documented accountability from collection to court

Chain of custody documents every person who handled the specimen, maintaining an unbroken record of accountability that ensures evidentiary integrity in court.