Dinoprost is the synthetic or partially synthetic, naturally-occurring prostaglandin F2 alpha (trade mark Prostin F2 alpha). Dinoprost has been used for therapeutic termination of pregnancy. Although the exact mode of action in pregnancy termination in humans is not fully defined, when Prostin F2 alpha is administered by the intrauterine route it initiates rhythmical uterine contractions which, if continued for a sufficient time, are capable of expelling the contents of the uterus. Sensitivity of the pregnant uterus to prostaglandins is lower during early and mid-pregnancy than at term.