Induction of lung tumors and lymphomas in BALB/c mice by metronidazole.

Metronidazole, which is widely used in the treatment of "Trichomonas vaginalis", "Entamoeba histolytica" and "Giardia lamblia" infections, was administered to BALB/c mice by stomach tube in an aqueous solution at a dose rate of 2 mg/day for 100 days (total 200 mg) to test its carcinogenicity. The treatment induced a significant increase in lung tumors in male mice (p less than 0.001) and provoked the appearance of lymphomas in females (p less than 0.001). Although there is insufficient evidence to pass judgement on the potential carcinogenicity of metronidazole in man, the results of this and other investigations reported in the literature have demonstrated that metronidazole develops carcinogenic activity in rats and mice.