I've been hearing some noise about this lately. What does the evidence show? I got six citations doing a PubMed search with the following strategy:
("acetylcysteine"[MeSH Terms] OR "acetylcysteine"[All Fields] OR "n acetyl cysteine"[All Fields]) AND non-acetaminophen[All Fields]
Here they are:
This small study compared treated patients with a historic controls and demonstrated reduced mortality. Oral NAC was used.
This recently published RCT used IV NAC and demonstrated improved transplant free survival if used early. (For patients with advanced encephalopathy nothing short of transplant seems to salvage them).
This Chest review of ALF makes mention of it as a possible modality in non-acetaminophen ALF.
This paper suggests efficacy and safety in the pediatric population.
This systematic review was negative but out of date, with no citations after 2003 included.
One other paper examined pathyphysiologic effects in mouse liver.
All in all the evidence for benefit is mounting and the treatment appears safe. Not standard of care yet but maybe worth a try.