Failure of methapyrilene to induce tumors in hamsters or guinea pigs

Abstract

In a small‐scale experiment, 12 male and 12 female strain 2 guinea pigs were treated by gavage twice a week for 78 wk with a 200‐mg/kg body weight dose of methapyrilene hydrochloride dissolved in water, a total dose of approximately 30 g/kg body weight. By the end of the treatment more than half of the animals were still alive: survivors were killed at 132 wk. A group of 20 male Syrian golden hamsters was treated twice a week by gavage with 15 mg methapyrilene hydrochloride for 58 wk, a total dose of approximately 15 g/kg body weight. Thirteen animals survived on acute convulsant effect, and the last 4 were killed at wk 61. There was no significant incidence of any tumor that could be attributed to the treatment in either guinea pigs or hamsters.