Effects of ivermectin on parameters of the estrous cycle, gestation and lactation of rats

Abstract

This work evaluates the estrous cycle, gestation and lactation of rats treated with ivermectin. Control (GI) rats received distilled water; and the remaining were treated during 45 days with ivermectin (GII=0.5; GIII=1.0; GIV=2.0; GV=4.0; GVI=8.0 and GVII=10.0 mg/kg) by the oral route, the drug being administered every three day, in a total of 15 administrations. Colpocytological examinations were then performed during 15 consecutive days. Four animals from each group were euthanized, and samples of ovaries and uteri were taken for histological evaluations. The remaining animals were mated and treated throughout the gestation period and further until the 15th postpartum day. Colpocytologic examinations revealed that the animals of groups II, III, IV, V, VI and VII presented a higher incidence of the estrus phase, in comparison with the control group (group I). Histopathologic studies showed that the groups treated with ivermectin presented an increased concentration of hyperplasic endometrial glands, whereas the morphology of the ovary was not altered. The treatment did not affect the gestation lenght, the number of newborns nor did it caused congenital mortality or newborns malformations. During lactation, there was a significant slowering of the body weight gain of the litter. It is concluded that the treatment of female rats with ivermectin increases the incidence of the estrus phase. In addition, a definite deleterious effect is exerted on nursing animals as revealed by the reduced body weight gain of the litter.