Studies of the interactions of clofibrate with the reproductive function

: The effect of various doses of clofibrate on the incidence of pregnancy, on the weight of gonads and seminal vesicles, on the estrous cycle, and on the elimination of 17-ketosteroids and estrogen through the urine was studied on the rat and the rabbit. Doses under 500 mg/kg were without effect. With doses of 500 mg/kg there was a marked decreas e in the incidence of pregnancy, a decrease in urinary estrogen, and the estrous cycle was inhibited. In the rat, the drug was found to inhibit the synthesis of cholesterol. Clofibrate appears to interfere with the production or metabolism of estrogen, but the nature of the interaction remains unknown. It is possible that clofibrate may act on the ovaries by preventing the movement of precursors of active steroids.