Deck 31: Clinical Toxicology

Question 1

An 18-year-old man who had been found unresponsive and face down in his bed after spending the day working in his garage is brought to the hospital emergency department.He had not responded to naloxone administration given by the paramedics.His history reveals that he was despondent over the recent death of his father,with whom he enjoyed restoring antique automobiles.Laboratory results indicate negative serum acetone,elevated serum urea and creatinine,normal PO₂,decreased bicarbonate,increased PCO₂,and increased osmol gap and anion gap.Urinalysis indicated many oxalate crystals.A second anion gap is calculated and the value has increased from the initial value.Based on these laboratory results and the likely compound that has affected this individual,what type of acid-base imbalance is present?

A) Respiratory acidosis
B) Respiratory alkalosis
C) Metabolic alkalosis
D) Metabolic acidosis

Answer 1

Metabolic acidosis

Question 2

Respiratory alkalosis is a clinical feature of overdose ingestion of salicylate because:

A) salicylates induce hyperventilation.
B) the central nervous system is stimulated to depress breathing.
C) uncoupling of oxidative phosphorylation occurs in all cells.
D) salicylates enhance anaerobic glycolysis.

Answer 2

salicylates induce hyperventilation.

Question 3

A drug of abuse that stimulates the central nervous system by blocking dopamine reuptake and rapidly metabolizes to inactive benzoylecgonine and ecgonine methyl ester is:

A) cocaine.
B) heroin.
C) methamphetamine.
D) ethanol.

Answer 3

cocaine.

Question 4

An 18-year-old man who had been found unresponsive and face down in his bed after spending the day working in his garage is brought to the hospital emergency department.He had not responded to naloxone administration given by the paramedics.His history reveals that he was despondent over the recent death of his father,with whom he enjoyed restoring antique automobiles.Laboratory results indicate negative serum acetone,elevated serum urea and creatinine,normal PO₂,decreased bicarbonate,increased PCO₂,and increased osmol gap and anion gap.Urinalysis indicated many oxalate crystals.Based on these laboratory results and the likely compound that has affected this individual,what are the metabolizing enzyme and the metabolite(s)formed from the toxic compound?

A) CYP2D6; morphine
B) Alcohol dehydrogenase; glycolic and oxalic acids
C) Alcohol hydroxylase; acetone
D) Aldehyde dehydrogenase; formaldehyde

Question 5

An 18-year-old man who had been found unresponsive and face down in his bed after spending the day working in his garage is brought to the hospital emergency department.He had not responded to naloxone administration given by the paramedics.His history reveals that he was despondent over the recent death of his father,with whom he enjoyed restoring antique automobiles.Laboratory results indicate negative serum acetone,elevated serum urea and creatinine,normal PO₂,decreased bicarbonate,increased PCO₂,and increased osmol gap (corrected for ethanol)and anion gap.Urinalysis indicated many oxalate crystals.Based on these laboratory results,what is the likely compound that has affected this individual?

A) Carbon monoxide
B) Methanol
C) Ethylene glycol
D) Codeine

Question 6

An individual is found unconscious with two empty pill bottles nearby,one of aspirin and the other of phenobarbital.The best antidote for this type of double drug overdose would be:

A) N-acetylcysteine.
B) forced alkaline diuresis.
C) hemodialysis.
D) atropine.

Question 7

In which one of the following specimen types is there a strong relationship between it and plasma free drug concentration,but the window of detection is short compared with that in a urine specimen?

A) Serum
B) Meconium
C) Oral fluid
D) Hair

Question 8

In a clinical laboratory without gas chromatography instrumentation,the common method of choice used to measure ethanol in serum or plasma is a(n):

A) enzymatic analysis using alcohol dehydrogenase and measurement of nicotinamide adenine dinucleotide (NADH)formation.
B) immunoassay using antibodies directed against acetaldehyde.
C) planar chromatography method combined with mass spectrometry.
D) potentiometric measurement of changes in voltage potential across electrodes.

Question 9

In a chronic user of marijuana,the metabolite will remain in urine for what period of time?

A) 2 to 7 days
B) 3 to 4 weeks
C) Up to 73 days
D) 3 to 4 months

Question 10

An 18-year-old man who had been found unresponsive and face down in his bed after spending the day working in his garage is brought to the hospital emergency department.He had not responded to naloxone administration given by the paramedics.His history reveals that he was despondent over the recent death of his father,with whom he enjoyed restoring antique automobiles.Laboratory results indicate negative serum acetone,elevated serum urea and creatinine,normal PO₂,decreased bicarbonate,increased PCO₂,and increased osmol gap and anion gap.Urinalysis indicated many oxalate crystals.Based on these laboratory results and the likely compound that has affected this individual,what is the best therapy?

A) Fomepizole
B) Increased naloxone dose
C) Folate administration
D) Activated charcoal

Question 11

Your toxicology testing facility tests urine samples.New screening tests for methamphetamine and amphetamine have been added to the drug profiles.Occasionally a positive methamphetamine immunoassay screening test is followed by a negative amphetamine confirmatory test result.What might cause this discrepancy?

A) Recent use of hydrocodone would give a negative amphetamine result,as it blocks the reaction on the screening test.
B) If the specimen contained ephedrine or pseudoephedrine,it might test positively for methamphetamine but not amphetamine.
C) False-negative results are common,especially when the immunoassay is performed without prior glucuronide hydrolysis.
D) Other chemically related compounds such as pseudoephedrine have been shown to produce positive results in amphetamine immunoassays.

Question 12

In the liver,methanol is metabolized by _____ to form _____.

A) aldehyde dehydrogenase; acetic acid
B) alcohol dehydrogenase; formaldehyde
C) methanol hydroxylase; acetaldehyde
D) . $\gamma$ -glutamyltransferase; water

Question 13

The most common laboratory method for detection,discrimination,and quantitation of alcohols in biological specimens is:

A) immunoassay.
B) HPLC.
C) spectrophotometry.
D) flame ionization gas chromatography (GC).

Question 14

Which one of the following best explains the toxic effect of acetaminophen overdose?

A) The coma produced is caused by an immediate decrease in sensitivity to CO₂ concentration through depression of respiratory centers in the brain.
B) The myocardial infarction is caused by the effect on respiratory centers in the brain and eventual lack of stimulation of the heart.
C) The hepatic necrosis is caused by depletion of a substance in the liver and eventual accumulation of the oxidized metabolite.
D) The metabolic acidosis produced is caused by increased formation of formic acid by the liver during metabolism.

Question 15

Following a school field trip to the country,four teenage boys are admitted to the hospital emergency department with visual system impairment and severe abdominal pain.Laboratory evaluation reveals metabolic acidosis,increased anion gap and osmol gap,negative serum acetone,and no unusual urine sediments.Intoxication by which of the following is most likely responsible?

A) Methanol
B) Carbon monoxide
C) Isopropanol
D) Ethanol

Question 16

An individual who appears to be very inebriated is brought to a hospital emergency department by the police.Laboratory blood gas results indicate metabolic acidosis with an increased serum osmol gap,the presence of serum acetone,and many urine oxalate crystals.Which alcohol did this individual ingest?

A) Isopropanol
B) Ethanol
C) Methanol
D) Ethylene glycol

Question 17

A type of drug test that is used to rule out the presence of drugs or to suggest the presence of a particular drug group and that has been replaced by rapid immunoassay tests is the _____ test.

A) gas chromatography
B) confirmatory
C) forensic drug
D) spot

Question 18

What is the major metabolite of acetaminophen that is formed in the liver?

A) Ascorbic acid
B) Formic acid
C) Sulfanilic acid
D) Glucuronide

Question 19

The correct formula for determining anion gap is:

A) [HCO
^-] - [Na⁺ + Cl^-].
B) [Na⁺] - [Cl^- + HCO
^-].
C) [Na⁺] + [Cl^- + HCO
^-].
D) [Cl^-] + [Na⁺ + HCO

Question 20

Which one of the following enzymes is inhibited by organophosphate or carbamate compounds,such as those found in pesticides?

A) Amylase
B) Alcohol dehydrogenase
C) Acetylcholinesterase
D) Alkaline phosphatase

Question 21

Laboratory analysis of which one of the following enzyme activities is performed to assess acute neurotoxicity from organophosphate or carbamate poisoning?

A) Aldehyde dehydrogenase
B) CYP2D6
C) Acetylcholinesterase
D) Transaminase enzymes

Question 22

The best antidote for overdose with heroin is:

A) activated charcoal.
B) naloxone.
C) forced alkaline diuresis.
D) forced acid diuresis.

Question 23

A positive urine immunoassay screening test for a drug of abuse must be confirmed by:

A) GC-MS.
B) a more sensitive and specific immunoassay procedure.
C) electrophoresis.
D) a spot test.

Question 24

Cocaine is subject to recreational abuse because it:

A) has CNS depressant effects resulting in sedation and hypnosis,and increases growth hormone release.
B) increases the effect of peripheral and central cholinergic nervous systems to induce feelings of happiness.
C) depresses the CNS but not the peripheral nervous system,depending on the blood ethanol concentration,to produce euphoria and decreased inhibition.
D) blocks dopamine reuptake at nerve synapses and prolongs the action of dopamine in the CNS,leading to feelings of euphoria.

Question 25

MATCHING
Match the compound with the appropriate antidote for overdose.
Hydroxycobalamin

A)Salicylic acid
B)Acetaminophen
C)Cyanide
D)Organophosphates

Question 26

The laboratory method of analysis that is accurate and precise for very low concentrations of carbon monoxide is:

A) spectrophotometry.
B) immunoassay.
C) gas chromatography.
D) potentiometry.

Question 27

An example of a nonbenzodiazepine sedative-hypnotic that is used in drug-facilitated sexual assault that interacts with a subtype of the GABA_A receptor complex is:

A) diazepam.
B) zolpidem.
C) chloral hydrate.
D) . $\gamma$ -hydroxybutyrate.

Question 28

The enzyme responsible for the metabolism of delta-9-tetrahydrocannabinol (THC)to its various metabolites is:

A) alcohol dehydrogenase.
B) CYP2D6.
C) CYP3A.
D) aldehyde dehydrogenase.

Question 29

MATCHING
Match the compound with the appropriate antidote for overdose.
N-acetylcysteine

A)Salicylic acid
B)Acetaminophen
C)Cyanide
D)Organophosphates

Question 30

Meconium is a difficult substance to analyze in a clinical laboratory for drug assessment because:

A) there is a shorter window of detection for drugs compared to urine.
B) it is a difficult material to work with,and drug testing is far less standardized than for a urine specimen.
C) external environmental exposure to drugs causes them to be falsely detected in this substance.
D) contains analytes that cross-react with most drug tests.

Question 31

Because of its rapid turnaround time,the laboratory method of choice used to screen urine samples for their opiate content is:

A) immunoassay.
B) gas chromatography.
C) liquid chromatography.
D) ferric chloride test.

Question 32

To recognize a poisoning pattern,groups of drugs with similar actions,symptoms,and clinical signs are examined.These common signs and symptoms are referred to as the:

A) metabolic pattern.
B) pattern constellation.
C) toxin effect.
D) toxidrome.

Question 33

MATCHING
Match the compound with the appropriate antidote for overdose.
Activated charcoal

A)Salicylic acid
B)Acetaminophen
C)Cyanide
D)Organophosphates

Question 34

MATCHING
Match the compound with the appropriate antidote for overdose.
Atropine

A)Salicylic acid
B)Acetaminophen
C)Cyanide
D)Organophosphates

Question 35

Match the compound with its metabolite.
Glycolic acid

A)Ethanol
B)Barbiturate
C)Heroin
D)Ethylene glycol

Question 36

Agents related to the anticholinergic toxidrome include all of the following except:

A) tricyclic antidepressants.
B) antihistamines.
C) phenothiazines.
D) organophosphates.

Question 37

A sympathomimetic drug that can be a drug of abuse but has legitimate pharmacologic use as a treatment for narcolepsy is:

A) fentanyl.
B) marijuana.
C) amphetamine.
D) diazepam.

Question 38

An individual is brought to the hospital emergency department with nausea,vomiting,and an altered mental status.An empty bottle of nonprescription enteric-coated acetylsalicylic acid (aspirin)was found at her bedside by her husband 30 minutes earlier.Although all signs and symptoms point to salicylate overdose,laboratory analysis indicated no acid-base disorder and low salicylate concentration using a photometric procedure.What is the explanation of this discrepancy?

A) Aspirin overdose does not produce toxic effects,so the emergency department physicians should request different laboratory tests.
B) The laboratory analyses were likely not specific or sensitive enough to discern the salicylate level or the acid-base disorder.
C) There has been too lengthy a period of time between pill ingestion and laboratory analysis,and all laboratory values have returned to normal levels.
D) The enteric-coated pills delayed aspirin absorption and blood work was collected before the salicylate could reach maximum concentration.

Question 39

You receive a filled purple-top (EDTA-containing)tube with a request for a cyanide assay that requires a whole blood sample.You:

A) realize that the tube you received will not yield any red blood cells,so you call to request a new sample collection.
B) realize that the tube you received will give you serum when separated,so you call to request a new sample collection.
C) know that the tube you received is perfectly fine if well mixed and proceed to run the sample to check for evidence of cyanide.
D) know that urine is the only specimen you can use for this type of assay,so you call to have a new sample collected.

Question 40

Match the compound with its metabolite.
Morphine

A)Ethanol
B)Barbiturate
C)Heroin
D)Ethylene glycol

Question 41

The long elimination half-life of marijuana that affects the duration of detection is due to the reentry of THC from tissue fat stores into the circulation.

Question 42

Match the compound with its metabolite.
Heroin

A)Ethanol
B)Barbiturate
C)Heroin
D)Ethylene glycol

Question 43

Match the compound with its metabolite.
Carboxylic acid

A)Ethanol
B)Barbiturate
C)Heroin
D)Ethylene glycol

Question 44

Match the compound with its metabolite.
Diazepam

A)Ethanol
B)Barbiturate
C)Heroin
D)Ethylene glycol

Question 45

Match the substance with the suggested antidote for its overdose.
Ethylene glycol

A)Flumazenil
B)Physostigmine
C)Ethanol
D)Methylene blue

Question 46

Match the toxicant with its specific effect.
Pesticides (carbamates)

A)Central nervous system depressant
B)Central nervous system stimulant
C)Blocks oxygen binding to hemoglobin
D)Interferes with enzyme action

Question 47

Match the substance with the suggested antidote for its overdose.
Anticholinergic agents

A)Flumazenil
B)Physostigmine
C)Ethanol
D)Methylene blue

Question 48

Match the toxicant with its specific effect.
Carbon monoxide

A)Central nervous system depressant
B)Central nervous system stimulant
C)Blocks oxygen binding to hemoglobin
D)Interferes with enzyme action

Question 49

Match the toxicant with its specific effect.
Methamphetamine

A)Central nervous system depressant
B)Central nervous system stimulant
C)Blocks oxygen binding to hemoglobin
D)Interferes with enzyme action

Question 50

Match the compound with its metabolite.
Acetaldehyde

A)Ethanol
B)Barbiturate
C)Heroin
D)Ethylene glycol

Question 51

Match the substance with the suggested antidote for its overdose.
Methemoglobinemia

A)Flumazenil
B)Physostigmine
C)Ethanol
D)Methylene blue

Question 52

Match the toxicant with its specific effect.
Ethanol

A)Central nervous system depressant
B)Central nervous system stimulant
C)Blocks oxygen binding to hemoglobin
D)Interferes with enzyme action

Question 53

Match the compound with its metabolite.
Cocaine

A)Ethanol
B)Barbiturate
C)Heroin
D)Ethylene glycol

Question 54

Match the substance with the suggested antidote for its overdose.
Benzodiazepine

A)Flumazenil
B)Physostigmine
C)Ethanol
D)Methylene blue