Lack of mutagenicity of diphenylhydantoin in in vitro short-term tests

The mutagenicity of diphenylhydantoin (DPH) and its major metabolite, 5-(p-hydroxyphenyl)-5-phenylhydantoin (HPPH), has been re-evaluated by the Ames test using Salmonella typhimurium and, for DPH only, by an in vitro cytogenetic test with human lymphocytes and a turbidimetric assay of tubulin polymerization. As negative results were obtained in all test systems used here, one has to conclude that DPH is devoid of mutagenic properties.