Philip Crowley, the author of the article, comments
Precautions listed in naltrexone’s product information include saying it may cause hepatocellular injury when given in excessive doses, and its use in patients with active liver disease must be carefully considered in light of its hepatotoxic effects. The product information also states that naltrexone is contraindicated in acute hepatitis or liver failure. This is based on a study in which 300 mg/day naltrexone was administered to obese patients. Five of 26 naltrexone recipients, and none of the placebo group, developed elevated serum transaminases after 3−8 weeks of treatment.1
Data on aspartate aminotransferase (AST) and alanine aminotransferase (ALT) have been used as an indicator of hepatotoxicity, with concentrations indicating both the effects of medication on hepatotoxicity, and reduced hepatotoxicity due to reduced alcohol consumption. Twelve of 1383 participants (0.9%) in the COMBINE study2 had elevated liver enzymes greater than five times the upper levels of normal. (Most cases were in the naltrexone group.) These effects resolved following discontinuation of the drug. This is the one study large enough to detect an adverse effect at this low level of incidence.
The study that Dr Mike McDonough refers to supports other smaller studies3,4 indicating that naltrexone was not hepatotoxic at the recommended dose in a trial of 74 participants.
I agree that often patients do better in a risk−benefit assessment when taking naltrexone compared to not taking it (because of concerns about minor liver enzyme changes).