Not a doctor and I wouldn't listen to medical advice from HN, but you can find a lot on this:
>Therefore, it may be beneficial to administer APAP(Tylenol) in combination with NAC routinely to reduce rates of liver failure and death. Because NAC's main role is to reduce the accumulation of APAP's toxic metabolites, the concomitant administration of NAC should have no impact on the efficacy of APAP as an antipyretic and analgesic.
>Therefore, it may be beneficial to administer APAP(Tylenol) in combination with NAC routinely to reduce rates of liver failure and death. Because NAC's main role is to reduce the accumulation of APAP's toxic metabolites, the concomitant administration of NAC should have no impact on the efficacy of APAP as an antipyretic and analgesic.
From: https://clinicaltrials.gov/ct2/show/NCT01137591 .