What is the role of progesterone in emergency contraception?

Updated: Oct 06, 2020
  • Author: Frances E Casey, MD, MPH; Chief Editor: Richard Scott Lucidi, MD, FACOG  more...
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Only the progestin levonorgestrel has been studied for use as emergency contraception. It is marketed as Plan B. Its treatment schedule comprises 1 dose of 750 mcg levonorgestrel taken as soon as possible and no later than 72 hours (for optimal effectiveness) but can be used up to 120 hours after unprotected intercourse.  Plan B One-Step is an enteric-coated 1.5mg levonorgestrel emergency contraceptive pill (E-LNG-ECP) that both dissolves and is absorbed in the intestine.   This high dose of levonorgestrel delays ovulation up until the point of LH surge through inhibition of follicular development and maturation.

In June 2013, the FDA approved Plan-B One-Step as a nonprescription product for all women of childbearing potential. This action complies with allowing levonorgestrel-containing emergency contraceptives to be available as OTC products without age or point-of-sale restrictions. [35]  Generic tablets were approved February 2014 and include My Way, Take Action, and Next Choice One-Dose.

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