[Hepatotoxicological studies of pyrazolone derivatives on rats. Part 2: The study of propyphenazone and phenazone (author's transl)].

In female rats the administration of 1,5 mmol/kg of, respectively, propyphenazone and phenazone over a period of 12 weeks produces a histologically detectable fatty degeneration and reactive-inflammatory changes of the liver, presumably caused by reactive metabolites. These slight morphological alterations do not lead to an increase in plasma enzyme activities. Only in case of phenazone administration, reduced increases in body weight are indicative of a toxic effect. The acceleration of hexobarbital degradation and N-demethylation and the increase in liver weight testify to the inductive activity of both these compounds.