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Determining the impact of combined hormonal contraceptives on ulipristal acetate

Alison Edelman, MD, MPH, Oregon Health & Science University, 2015

Project abstract

The availability of highly effective options for emergency contraception is critical for women wanting to avoid pregnancy following an act of unprotected intercourse. An antiprogestin, ulipristal acetate (UPA; ella™), has emerged as one of the most effective oral options. We currently lack critical information regarding the practical use of UPA. In vitro studies have shown that UPA binds to and prevents progesterone receptor signaling, leading to the theoretical concern that progestin-containing hormonal contraceptives would negate UPA action.

Ideally, we want women to initiate routine contraception following emergency contraceptive use. However at this time, there is little evidence to guide a woman choosing to take UPA and wanting to initiate a hormonal method. She can delay initiation of hormonal contraception and continue to be at risk for pregnancy or immediately initiate her method and possibly decrease the efficacy of UPA.

Our proposal has been designed to address this gap in knowledge and will focus on the impact of combined hormonal contraceptives on UPA’s main mechanism of action. Our hypothesis is that starting combined oral contraceptives 2 days after UPA use adversely impacts UPA’s ability to delay ovulation.

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