Blood levels of acetaminophen correlate with liver damage in overdosage situations.
Specimen:
Accurate interpretation requires a well-timed specimen, but often the exact time of ingestion is not known with certainty. The specimen must be drawn at least 4 hours after ingestion; liver toxicity cannot be predicted from blood levels earlier than 4 hours.
From the nomogram, we can derive the following equations for the line defining serious toxicity:
LOG10 (serum/plasma acetaminophen concentration for serious toxicity, µg/mL) =
= (-0.075 * (hours since ingestion)) + LOG10 (400) =
= (-0.075 * (hours since ingestion)) + 2.6
serum or plasma acetaminophen concentration for serious toxicity, µg/mL =
= 10^ ((-0.075 * (hours since ingestion)) + 2.6)
Interpretation
If the serum level is above the value at a given time, then hepatotoxicity is likely.
Blood Levels
Severe Liver Disease
No Significant Liver Disease
at 4 hours
200 µg/mL
< 150 µg/mL
at 12 hours
> 50 µg/mL
< 30 - 35 µg/mL
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