Reproductive Safety Studies of Oxfendazole in Sheep and Cattle

Abstract

The safety of oxfendazole when administered to the pregnant ruminant and to rams during the breeding season was assessed. Doses of the anthelmintic three times in excess of those recommended for therapeutic use were administered to pregnant ewes and heifers during the critical period of embryo organogenesis and implantation, to pregnant ewes within one month of lambing and to two rams repeatedly from 21 days prior to and throughout the breeding season. Administration in overdose to ewes in the third week of pregnancy, when the ovine embryo is particularly sensitive to teratogenic effects of benzimidazole compounds, was shown to be without effect on the subsequent progeny; dosing in late pregnancy was also shown to have no effect on the ewe or on perinatal viability of the lambs. Oxfendazole proved to be safe and without teratogenic effect when administered repeatedly and in overdose to heifers during early pregnancy and had no adverse effect on fertility in rams during repeated dosing over periods of eight to 10 weeks.