Reproductive toxicity studies of benzalazine in rats and rabbits.

Embryotoxicity studies of benzalazine (2-hydroxy-5-[(4-carboxyphenyl) azo]benzoic acid, CAS 64896-26-0), a new agent for the treatment of ulcerative colitis and Crohn's disease of the large intestine, were performed in rats and rabbits. Benzalazine elicited no evidence of teratogenicity when administered orally during the fetal organogenesis period to pregnant rats at doses up to 2000 mg/kg b.w./d, or to pregnant rabbits at doses up to 1000 mg/kg b.w./d. Rat fetuses in the 400 and 2000 mg/kg groups exhibited decreased body weights; the placentae weights were decreased in these dose groups, too. Rabbit fetuses in the high-dose group (1000 mg/kg b.w./d p.o.) also showed decreased body weights. Decreased body weight gain and reduced food intake were seen in rat dams in the high-dose group (2000 mg/kg b.w./d p.o.). In rabbit dams a decrease in body weight gain in the high-dose group (1000 mg/kg b.w./d p.o.) and a dose-dependent reduction in food intake from 200 mg/kg b.w./d p.o. onwards were noted. No further disturbances were observed in the behaviour of the rat and rabbit dams. External appearance, faeces, consumption of drinking water and macroscopical inspection during autopsy did not indicate any influence of the test compound. No retardations or malformations were seen even at the highest tested dose levels (rat: 2000 mg/kg b.w./d p.o.; rabbit: 1000 mg/kg b.w./d p.o.).