Mifepristone blocks the hormone progesterone, which is needed to sustain a pregnancy. This results in:
Changes in the uterine lining and detachment of the pregnancy;
Softening and opening of the cervix; and
Increased uterine sensitivity to prostaglandin.
Mifepristone is used in combination with another medication, a prostaglandin analogue called misoprostol. Misoprostol causes the uterus to contract and helps the pregnancy tissue to pass.