# Evaluation of cut-off values in acute paracetamol poisoning for safe termination of N-acetylcysteine

## TL;DR

This study evaluates factors affecting paracetamol detection after 15 hours to guide N-acetylcysteine treatment in poisoning cases.

## Contribution

The study identifies new cut-off values and risk factors for paracetamol detection to improve treatment decisions in acute poisoning.

## Key findings

- 30 out of 194 patients had detectable paracetamol after 15 hours.
- Time to presentation strongly predicts toxic concentration (Odds ratio = 1908).
- Ingested dose and elevated liver enzymes are significant for detectable paracetamol.

## Abstract

The Rumack-Matthew nomogram has been utilized to predict hepatotoxicity from acute paracetamol poisoning. Where paracetamol concentrations are unavailable, the commencement and cessation of treatment rely on reported dose. This study aimed to investigate risk factors predicting detection of paracetamol after 15 h.

A retrospective analysis was conducted at two emergency centers from 2010 to 2020. Patients aged ≥ 14 years who ingested ≥ 75 mg/kg within 15 h were included. Exclusion criteria were chronic liver disease, taking multiple doses, sustained-release formations, or activated charcoal administration. Multinomial logistic regression was used to assess risk factors for detection of paracetamol after 15 h, and the area under the curve was calculated.

Among one hundred and ninety-four patients, 30 patients (15.4%) had detectable paracetamol and 7 patients (3.6%) showed toxic concentration after 15 h, and median ingested dose was 152.8 mg/kg. Time to presentation was significant for toxic concentration (Odds ratio = 1908), the area under the curve was 0.969, 612 min cut-off. Ingested dose and elevated liver enzyme were valid for detectable concentration (Odds ratio = 2.118 and 4.458), the area under the curve of ingested dose was 0.633, 105.2 mg/kg cut-off.

Where paracetamol concentrations are unavailable and the United Kingdom guideline followed, for patients ≥ 14 years who present within 15 h and report ingestion ≥ 75 mg/kg, maximum therapeutic dose, N-acetylcysteine should be initiated. Furthermore, for patients who present after 10 h, ingested > 105.2 mg/kg or report elevated liver enzyme, supplementary N-acetylcysteine is strongly advised.