Effect of phenobarbitone on plasma and hepatic alkaline phosphatase activity in the dog

An increase of plasma alkaline phosphatase activity may occur in dogs treated with phenobarbitone, which is not associated with hepatobiliary obstruction or bone damage, but is accompanied by increased activity of hepatic alkaline phosphatase and hepatic drug-metabolising enzymes. Electron microscopy reveals proliferation of smooth endoplasmic reticulum but no evidence of hepatocellular damage. These results counsel caution in the interpretation of increased plasma alkaline phosphatase activity in toxicological studies and human clinical practice.