FPGEE Toxicology 3

Question 1

A patient ingests methanol and presents with an elevated anion gap, elevated osmol gap, and visual disturbances. What toxic metabolite causes the ocular damage?

Accepted Answer

Formic acid

Answer

Methanol is metabolized by alcohol dehydrogenase to formaldehyde and then formic acid, which inhibits cytochrome oxidase and causes optic nerve toxicity.

Question 2

Fomepizole (4-MP) is used to treat methanol and ethylene glycol poisoning because it:

Accepted Answer

Inhibits alcohol dehydrogenase

Answer

Fomepizole is a potent inhibitor of alcohol dehydrogenase, preventing conversion of methanol and ethylene glycol to their toxic metabolites.

Question 3

Which of the following best describes the mechanism of toxicity of carbon monoxide?

Accepted Answer

It displaces oxygen by binding hemoglobin with higher affinity and inhibits cellular respiration

Answer

CO binds hemoglobin with 250 times the affinity of oxygen forming carboxyhemoglobin and also inhibits cytochrome oxidase, causing both impaired oxygen delivery and cellular hypoxia.

Question 4

A patient with salicylate toxicity has a blood pH of 7.5 and urine pH of 6.5. What urinary manipulation should be performed to enhance elimination?

Accepted Answer

Alkalize the urine with sodium bicarbonate

Answer

Urinary alkalinization with sodium bicarbonate raises urine pH, trapping ionized salicylate in the tubular lumen and dramatically increasing renal clearance.

Question 5

Which opioid has a significantly longer duration of action than naloxone, requiring repeated dosing or a naloxone infusion?

Accepted Answer

Methadone

Answer

Methadone has a half-life of 24-60 hours, far exceeding naloxone's 60-90 minutes, necessitating repeat doses or a continuous naloxone infusion to prevent re-narcotization.

FPGEE Exam Practice Test

FPGEE Exam Practice Test

FPGEE Toxicology 3