Question 1

Select the correct pairing of toxin - antidote:&#10;A) Penicillamine - iron&#10;B) EDTA - copper&#10;C) Deferoxamine - lead&#10;D) Methanol - ethanol&#10;E) Carbon monoxide - nitrous oxide

Accepted Answer

The toxic effects of methanol are largely mediated by two of its metabolites, formaldehyde and formic acid. Ethanol competes with methanol as a substrate of hepatic alcohol dehydrogenase, thereby slowing the rate of formaldehyde synthesis. This decreases peak formaldehyde levels and allows for more methanol to be excreted unchanged by the kidney and lungs.

Question 2

Which of the following is not recommended in the treatment of the patient suffering from cyanide toxicity?&#10;A) Sodium nitrite&#10;B) Sodium thiosulfate&#10;C) Supplemental oxygen&#10;D) Hydroxocobalamin&#10;E) Methylene blue

Accepted Answer

Methylene blue is used to treat methemoglobinemia. It acts to reduce heme iron from the ferric state to the ferrous state. Under normal circumstances, methemoglobinemia is undesirable, because of the reduced oxygen-carrying capacity of ferric iron. However, ferric iron avidly binds cyanide and prevents its cellular uptake. Therefore, in the case of cyanide toxicity, a degree of methemoglobinemia is beneficial.

Question 3

Choose the correct statement of the following:&#10;A) The deleterious effects of most toxic substances are confined to a single organ system.&#10;B) The lungs do not have a significant role in the biotransformation of toxic chemicals.&#10;C) By helping to clear the foreign substance, the immunologic system has a primarily beneficial role in response to nickel exposure.&#10;D) Common targets of neurotoxins include axonal transport and neurotransmitter release.&#10;E) Benzene toxicity is primarily autoimmune-mediated by immunologic overstimulation.

Accepted Answer

Common targets of neurotoxins include axonal transport and neurotransmitter release. The other choices are incorrect. A is incorrect because toxic substances can affect multiple organ systems. B is incorrect because the lungs can play a role in biotransformation. C is incorrect because the immune system may not always have a beneficial response to exposure to toxic substances. E is incorrect because benzene toxicity is not primarily autoimmune-mediated.

Deck 8: Principles of Toxicology