June 18, 2001: What are the current recommendations for the administration of N-acetylcysteine(NAC) following APAP overdose?

When indicated, NAC should be administered within 8 hours of ingestion of APAP.  The efficacy of the drug in preventing hepatotoxicity decreases each hour after 8 hours.  There is no benefit in giving the drug at hour 2 rather than at hour 7 after ingestion. So if the patient presents close to 8 hours after APAP ingestion, administer NAC and obtain serum APAP concentrations.  If further treatment is not indicated, there has been no harm done and the patient can be discharged.

If the serum concentration falls above the line on the nomogram, admission and NAC  treatment is indicated.  NAC administration can be discontinued at 36 hours if liver enzymes remain normal. 

Due to the odor of sulfhydryl groups,  children frequently vomit following NAC administration.  Administering NAC in a "sippy cup" increases the tolerance.  If they vomit after the initial dose of NAC, the loading dose should be repeated. Ondansterone(Zofran) works well to prevent vomiting.  Wait 30 minutes after the administration of Zofran before repeating the NAC dose.