Tumorigenic effect of 1-hydrazinophthalazine hydrochloride in mice.

A solution of 0.125% 1-hydrazinophthalazine hydrochloride, an antihypertensive drug widely used in humans, was given continuously in drinking water for the life-spans of randomly bred Swiss mice. Consumption of the chemical significantly increased the lung tumor incidence from 36 to 60% in females and from 26 to 46% in males, compared to controls. Histopathologically, the tumors were classified as adenomas and adenocarcinomas of the lungs.