Mutagenicity testing of selected analgesics in Ames Salmonella strains

Acetaminophen (APAP), aspirin (ASA), phenacetin (PA) and ibuprofen (IB) were tested for mutagenic activity in the Ames Salmonella plate incorporation assay using strains TA98, TA100, TA1535, TA1537 and TA1538. These analgesics were tested in four separate tests: without metabolic activation, and in the presence of a rat, hamster or mouse liver post-mitochondrial supernatant (S-9, Aroclor 1254-induced). Treatment of all five strains of Salmonella with APAP, ASA or IB under all four metabolic conditions did not induce any appreciable increases in revertant colony counts, as compared to the negative controls. A dose-related increase in revertant colony counts, reaching levels twice the negative control values, were seen with PA at doses greater than or equal to 500 micrograms per plate. This response was only seen in strain TA100 in the presence of hamster S-9. Therefore, these findings constitute a positive result for PA in the Ames test. APAP, ASA and IB did not show any mutagenic potential under these conditions of testing. These findings are discussed along with previously published results concerning the genotoxicity of these analgesics.