[Experimental study of the carcinogenicity of phenacetin]

150 rats and 100 mice were treated subcutaneously (once weekly) and orally (2-5 times a week) with single doses of phenacetin (300-1,000 mg/kg and 800 mg/kg suspended in sunflower oil, respectively). 100 rats and 100 mice in control received sunflower oil alone. Tumor incidence in rats after subcutaneous treatment was 14% and 20%--after oral treatment; in control rats--5 and 5.1%, in experimental mice--33 and 34% and in control mice--5 and 7%, respectively. Mean latent period of tumor induction was noted to be shorter in experimental animals than in controls. Whatever the route of administration, the rats developed precancerous lesions and tumors in the urethra and bladder, hyperplastic changes in the bronchi and adenocarcinoma in lungs as well as single tumors of mammary gland, skin and subcutaneous fat. Hepatocellular hyperplasia, single liver and kidney tumors were observed in mice. Increased tumor incidence in lungs, hemopoietic system and lymphoreticular tissue was higher in experimental mice than in controls. Experimental results evidence weak carcinogenic activity of phenacetin for rats and mice.