ABT Clinical Toxicology 2 — Questions and Answers
Question 1: Which treatment is first-line for cyanide poisoning in the United States?
- Sodium thiosulfate alone
- Hydroxocobalamin (Correct answer)
- Methylene blue
- Amyl nitrite alone
Correct answer: Hydroxocobalamin
Hydroxocobalamin (Cyanokit) is the preferred first-line antidote for cyanide poisoning in the US, binding cyanide to form cyanocobalamin excreted in urine.
Question 2: Methylene blue is the antidote for which toxicological condition?
- Carbon monoxide poisoning
- Methemoglobinemia (Correct answer)
- Cyanide toxicity
- Lead poisoning
Correct answer: Methemoglobinemia
Methylene blue reduces methemoglobin back to functional hemoglobin via the NADPH-methemoglobin reductase pathway.
Question 3: A urine drug screen using immunoassay is most prone to which analytical problem?
- False negatives from dilution only
- Cross-reactivity causing false positives (Correct answer)
- Inability to detect opioids
- Degradation of all metabolites within 1 hour
Correct answer: Cross-reactivity causing false positives
Immunoassay urine drug screens are class-specific and can yield false positives due to cross-reactivity with structurally similar compounds.
Question 4: Which mechanism explains salicylate-induced hyperthermia in severe toxicity?
- Inhibition of cyclooxygenase
- Uncoupling of oxidative phosphorylation (Correct answer)
- Direct CNS fever center activation
- Peripheral vasodilation only
Correct answer: Uncoupling of oxidative phosphorylation
Salicylates uncouple oxidative phosphorylation in mitochondria, generating excess heat rather than ATP, leading to hyperthermia.
Question 5: Which of the following is a contraindication to ipecac syrup administration in poisoned patients?
- Aspirin ingestion within 30 minutes
- Caustic or corrosive substance ingestion (Correct answer)
- Activated charcoal unavailability
- Age over 12 years
Correct answer: Caustic or corrosive substance ingestion
Ipecac is contraindicated after caustic ingestion because vomiting can worsen esophageal and oropharyngeal injury from re-exposure to the substance.
Question 6: Carbon monoxide poisoning is treated with 100% oxygen primarily because it:
- Neutralizes CO in the bloodstream chemically
- Competitively displaces CO from hemoglobin by mass action (Correct answer)
- Stimulates erythropoiesis to replace damaged RBCs
- Increases renal excretion of carboxyhemoglobin
Correct answer: Competitively displaces CO from hemoglobin by mass action
High-flow 100% oxygen competitively displaces carbon monoxide from hemoglobin via mass action, reducing carboxyhemoglobin half-life from ~5 hours to ~60–90 minutes.
ABT Clinical Toxicology 2
Which treatment is first-line for cyanide poisoning in the United States?