EllaOne: a second-generation emergency contraceptive?

What is EllaOne? EllaOne contains 30 mg ulipristal acetate (UPA), a synthetic selective progesterone receptor modulator, which has antagonistic and partial agonistic effects at the progesterone receptor level. Consequently, UPA should prevent the gene transcription normally activated by progesterone to produce the necessary proteins to support pregnancy. Over the last 10 years, other progesterone receptor modulators have been studied and shown to be effective postcoital contraceptives;2,3 however, interest grew in using UPA as, in contrast to those previously studied, it has little anti-glucocorticoid activity.4