Measure APAP concentration at 4 hours from time of ingestion and plot on Rumack-Matthew Nomogram.Definition: Entire ingestion occurring within 8-hour period.

In other words, ~1% of patients below the line who are untreated will develop hepatotoxicity (defined as transaminitis) With this cutoff, failure rate of the line in acute ingestions is ~1%.In the US, the line was further arbitrarily lowered 25% to current “150-line” from =150 at 4 hours to =37.5 at 12 hours (purple line above).With this threshold, only 60% of patients above the line would go on to develop hepatotoxicity.Threshold initially lowered to a “200-line” from =200 at 4 hours to =50 at 12 hours (dotted yellow line above) to be more conservative.This approach led to a “300-line” from =300 at 4 hours to =50 at 12 hours (not pictured above) dividing patients with hepatotoxicity and those without. Empirically derived by plotting untreated patients with acute APAP ingestion on the graph above and dividing those who developed hepatotoxicity from those who didn’t (defined as AST/ALT >1000).X-axis: Hours post-ingestion Y-axis APAP concentration.

Antidote paracetamol toxicity