The F.D.A. said it made the change now because it had completed a review of a 2018 application to alter the label that was submitted by Foundation Consumer Healthcare, a company that in 2017 bought the Plan B brand from Teva Pharmaceutical Industries. Agency officials said the pandemic delayed the review process and that the timing was not motivated by political considerations.
Plan B One-Step and its generic versions — including brands like Take Action, My Way and Option 2 — contain levonorgestrel, one of a class of hormones called progestins that are also found at lower doses in birth control pills and intrauterine devices. The pills are most effective in preventing pregnancy if taken within 72 hours of sexual intercourse, although they can sometimes work if taken within five days.
Another type of morning-after pill, marketed as Ella and containing a compound called ulipristal acetate, is only available by prescription and is not affected by the F.D.A.’s label change. There has been less research on this type of pill, but studies suggest that it is highly unlikely to prevent implantation of a fertilized egg. In 2009, after months of scrutiny, Ella was approved for sale in overwhelmingly Catholic Italy, where laws would have barred it if it had been considered to induce abortions.
According to data published in 2021 by the Centers for Disease Control and Prevention, nearly one-quarter of women of reproductive age who have sex with men answered yes to the question: “Have you ever used emergency contraception, also known as ‘Plan B,’ ‘Preven,’ ‘Ella,’ ‘Next Choice,’ or ‘Morning after’ pills?” The agency did not break down the data by the type of pills taken.
As far back as the 1999 approval process, the maker of Plan B — Barr Pharmaceuticals, later acquired by Teva — asked the F.D.A. not to list an implantation effect on the label, The Times reported in 2012.
Experts said implantation was likely placed on the label partly because daily birth control pills, some of which contain Plan B’s active ingredient, appear to alter the endometrium, the lining of the uterus into which fertilized eggs implant. Altering the endometrium has not been proven to interfere with implantation. But in any case, scientists said that unlike the accumulating doses of daily birth control pills, morning-after pills do not have time to affect the uterine lining.
By 2007, evidence was accumulating that morning-after pills did not block implantation. In 2009 to 2010, during discussions about making Plan B available over the counter for all ages, Teva also asked that implantation be deleted from the label.
