It is a widely held belief that Tylenol (acetaminophen, or paracetamol, depending on where you are) should not be used in patients with chronic liver disease or transaminitis because the drug will worsen liver injury or cause acetaminophen toxicity, the most common kind of drug-induced liver injury. However, underuse of Tylenol may lead to overuse of other pain medications, like NSAIDs or opiates, which come with their own problems.
This review in the British Journal of Clinical Pharmacology goes through studies of healthy adults and adults with liver disease, including cirrhosis to look at the evidence for our fear of Tylenol. Essentially, the studies on Tylenol are small, and ALT naturally fluctuates (thus some of the previous methodology linking rise in ALT and Tylenol may have been questionable). The authors conclude that heavy alcohol use, malnutrition/fasting, underweight status, and sepsis may put patients at risk for acetaminophen toxicity, but Tylenol is still not 100% contraindicated for these groups. They state:
We have not found any case reports of hepatotoxicity secondary to therapeutic doses of paracetamol in adults with pre‐existing CLD who did not have at least one of these risk factors.
Therapeutic dose of acetaminophen is 4 g/24 hours. Therefore, it’s recommended that if you have patients with the above risk factors, aim to give them 2-3 g/24 hours. If they are developing rapidly deteriorating liver function (acute liver injury or failure), then it might be time to stop.