NBME 13 Induction of cytochrome P450 (NBME Answers)

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Retired NBME 13 Answers

nbme13/Block 3/Question#5 (reveal difficulty score)
A previously healthy 42-year-old Asian woman ...
Induction of cytochrome P450 🔍 / 📺 / 🌳 / 📖
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submitted by ∗iceberglettuce(15)

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Chronic EtOH induces CytP450. Acetaminophen metabolism yields NAPQI, which is highly hepatotoxic.

CytP450 inducers: CRAP GPS

Carbamazepine Rifampin Alcohol (chronic) Phenytoin

Griseofulvin Phenobarbitol St. John's wart

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submitted by ∗imgdoc(183)

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Acetaminophen normally is degraded by hepatic glucoronidation, but in chronic acetaminophen users, this pathway becomes "saturated". So the body uses the Cyt. P-450 enzyme system to convert it to N-acetyl-benzoquinonemine (NAPQI), which causes free radical damage. The question asks, which of the following effects of alcohol most likely contributed to this patients condition?

A,B,C,D are all anti free radical generation, and would not contribute to this patients condition. This leaves E, Alcohol is an inducer (basically ramps up CYT p450) of the P450 enzyme system which causes elevated levels of NAPQI.

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