The effect of ritodrine on PgE levels in pregnant rabbit vena cava blood.

A chronic model was utilized in the rabbit to determine the effect of ritodrine hydrochloride infusions on pregnancy. Infusions were carried out for 6 hours in the unanesthetized, conscious animal between the 25 to 27 day of pregnancy. Pre and post infusion blood samples were drawn from a catheter lying at the lower inferior vena cava and analyzed for prostaglandin E and F, and progesterone. As compared to a control animal, there was a significant fall in prostaglandin E after 6 hour infusion of drug, but no change in prostaglandin F or progesterone was observed.