injuries poisoning
Acetaminophen Poisoning
ChronicAcetaminophenPoisoning
Chronic excessive use or repeated overdoses cause hepatotoxicity in a few patients. Usually, chronic overdose is not an attempt at self-injury but instead results from taking inappropriately high doses to treat pain. Symptoms may be absent or may include any of those Symptoms and Signs . Aspartate aminotransferase (AST), alanine aminotransferase (ALT), and serumacetaminophenlevels The Rumack-Matthew nomogram cannot be used, but likelihood of clinically significant hepatotoxicity can be estimated based on AST, ALT, and serumacetaminophenlevels. If AST and ALT levels are normal (<50 IU/L [0.83 microkat/L]), and theacetaminophenlevel is<10 mcg/mL (<66 micromol/L), significant hepatotoxicity is very unlikely. If AST and ALT levels are normal but theacetaminophenlevel is≥10 mcg/mL (≥66 micromol/L), significant hepatotoxicity is possible; AST and ALT levels are remeasured after 24 hours. If repeat AST and ALT levels are normal, significant hepatotoxicity is unlikely; if the levels are high, significant hepatotoxicity is assumed. If initial AST and ALT levels are high, regardless of theacetaminophenlevel, significant hepatotoxicity is assumed. SometimesN-acetylcysteine The role ofN-acetylcysteinein treatment of chronicacetaminophentoxicity or in the presence of established acute hepatotoxicity is unclear. Theoretically, the antidote may have some benefit if given>24 hours after an ingestion if residual (unmetabolized)acetaminophenis present. The following approach has not been proved effective but may be used: If hepatotoxicity is possible (if aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels are normal andacetaminophenlevel is initially elevated),N-acetylcysteineis given 140 mg/kg orally loading dose and 70 mg/kg orally every 4 hours for the first 24 hours. If repeat AST and ALT levels (after 24 hours) are normal,N-acetylcysteineis stopped; if repeat levels are high, they are remeasured daily, and-acetylcysteineis continued until levels are normal. If hepatotoxicity is likely (especially if initial AST and ALT levels are high), a full course of-acetylcysteineis given (ie, loading dose as above, then 70 mg/kg every 4 hours for 17 doses). Prognostic factors are similar to those in acuteacetaminophenpoisoning. 