This dose is repeated 12 hours later. Nausea or vomiting is very rare, in most cases the woman will have not the slightest discomfort. This very simple and reliable protocol may prevent many abortions. This is also a means to prevent an abortion and, if the IUD is left in the uterus, a very reliable means to prevent further pregnancies. Insertion when a pregnancy is already established mostly has no effect and may be dangerous because it may cause infection in a pregnant uterus.
Progesterone is necessary to maintain the pregnancy.
In the presence of RU 486 part of the cell receptors which normally combine with progesterone are blocked by combining with this compound. This blocking is proportional with the concentration of RU 486. By taking 600 mg of RU 486 by mouth a young pregnancy may be terminated. Eric Schaff proved that smaller doses, like 200 mg had the same effect, so we do not see the advantage of 600 mg considering the high costs of the drug. With the onset of the luteo placental shift the effect gradually diminishes because of the rising concentration of progesterone.