Metronidazole: absence of mammalian cytogenicity.

Metronidazole was examined for cytogenicity in vivo and in vitro in mice and humans. In the micronucleus test in mice metronidazole was given either as, 2 oral doses 24 h apart, or, as a daily dose for 7 days. Neither forms of treatment produced any increase in the micronucleus frequency at doses up to 4 000 mg/kg. No increase in the chromosomal aberration frequency was found in human lymphocytes treated in vitro with metronidazole. The lymphocytes of 12 patients receiving metronidazole for vaginal trichomoniasis were examined for chromosomal aberrations. No increase for any type of aberration was found. Thus, metronidazole exhibits no cytogenetic activity in mammalian cells either in vitro or in vivo.