No carcinogenicity was observed in rats given orally for 2 consecutive years at a dose of 20mg/Kg (equivalent to approximately 15 times the clinically recommended maximum daily oral dose for adults or 10 times the clinically recommended maximum daily dose for children, in terms of body surface area). In the carcinogenicity test of mice administered orally for 2 consecutive years, the dose of 16mg/Kg (in terms of body surface area, approximately 6 times of the clinically recommended maximum daily oral dose for adults or 4 times of the clinically recommended maximum daily dose for children) was associated with an increased incidence of benign tumors in male animals. There was no increase in the incidence of liver tumors at a dose of 4mg/Kg (equivalent to approximately twice the clinically recommended maximum daily oral dose for adults, or clinically recommended maximum daily dose for children, in terms of body surface area). The clinical significance of these findings is not yet apparent.