A metabolomic analysis of thiol response for standard and modified N-acetyl cysteine treatment regimens in patients with acetaminophen overdose

Abstract

N-acetylcysteine (NAC) is an antidote to prevent acetaminophen (paracetamol-APAP)-induced acute liver injury (ALI). The 3-bag licensed 20.25 h standard regimen, and a 12 h modified regimen, are used to treat APAP overdose. This study evaluated the redox thiol response and APAP metabolites, in patients with a single APAP overdose treated with either the 20.25 h standard or 12 h modified regimen. We used liquid chromatography tandem mass spectrometry to quantify clinically important oxidative stress biomarkers and APAP metabolites in plasma samples from 45 patients who participated in a randomized controlled trial (SNAP trial). We investigated the time course response of plasma metabolites at predose, 12 h, and 20.25 h post-start of NAC infusion. The results showed that the 12 h modified regimen resulted in a significant elevation of plasma NAC and cysteine concentrations at 12 h post-infusion. We found no significant alteration in the metabolism of APAP, mitochondrial, amino acids, and other thiol biomarkers with the two regimens. We examined APAP and purine metabolism in overdose patients who developed ALI. We showed the major APAP-metabolites and xanthine were significantly higher in patients with ALI. These biomarkers correlated well with alanine aminotransferase activity at admission. Receiver operating characteristic analysis showed that at admission, plasma APAP-metabolites and xanthine concentrations were predictive for ALI. In conclusion, a significantly higher redox thiol response with the modified NAC regimen at 12 h postdose suggests this regimen may produce greater antioxidant efficacy. At baseline, plasma APAP and purine metabolites may be useful biomarkers for early prediction of APAP-induced ALI.

FIGURE 1

Alanine aminotransferase (ALT) and acetaminophen (APAP)‐cysteine levels in patients with acute liver injury (ALI; n = 4), as defined by >50% ALT rise at 20.25 h, and patients without ALI (no ALI; n = 40). (a) Serum ALT level at admission in patients stratified by ALI (n = 4) and no ALI (n = 40). (b) Plasma APAP‐cysteine level is expressed as a ratio of metabolite formed by APAP‐cysteine relative to APAP drug (APAP‐CYS/APAP) (%) at admission in ALI (n = 4) and no ALI (n = 40) patients. (c) Area under the curve (AUC) for APAP‐CYS is expressed as a fraction of APAP‐CYS (APAP‐CYS/APAP) (%) from time 0 to 20.25 h (AUC_0–20.25 h) after initiation of N‐acetylcysteine (NAC) in ALI (n = 4) and no ALI (n = 40) patients. (d) Correlation between the AUC of APAP‐cysteine expresses as a fraction of APAP‐CYS (APAP‐CYS/APAP) (%) from time 0 to 20.25 h (AUC_0–20.25 h) after initiation of NAC and serum ALT at admission in ALI (n = 4) and no ALI (n = 40) patients. All measurements were log‐transformed and reported by geometric means and ratios. (a–c) Box plots represent median (interquartile range) and whisker represents range. Pairwise comparison was performed by Mann–Whitney U test. (d) Spearman correlation was performed. *p < 0.05, **p < 0.005. CI, confidence interval

FIGURE 2

Purine metabolites level in patients with acute liver injury (ALI) (n = 4), as defined by >50% alanine aminotransferase (ALT) rise at 20.25 h, and patients without ALI (no ALI; n = 40). (a) Plasma purine metabolites concentration (µM) are expressed as the total metabolites formed (hypoxanthine, xanthine, uric acid, and allantoin) from time 0 to 20.25 h after initiation of NAC in ALI (n = 4) and no ALI (n = 40) patients. (b) Area under the curve (AUC) for xanthine is expressed as a fraction of xanthine metabolite relative to total purine metabolites (xanthine/total) (%) from time 0 to 20.25 h after initiation of NAC (AUC_0–20.25 h) in ALI (n = 4) and no ALI (n = 40) patients. (c) Correlation between the AUC for xanthine expressed as a fraction of xanthine metabolite relative to total purine metabolites (xanthine/total) (%) from time 0 to 20.25 h after initiation of NAC (AUC_0–20.25 h) and serum ALT) at admission in all patients (n = 44). All measurements were log‐transformed and reported by geometric means and ratios. (a–b) Box plots represent median (interquartile range) and whisker represents range. Pairwise comparison was performed by Mann–Whitney U test. (c) Spearman correlation was performed. *p < 0.05, **p < 0.005, ***p < 0.0001. CI, confidence interval