The appeals court ruling was issued unanimously by a conservative three-judge panel on Friday, significantly curtailing access to the drug nationwide and particularly in states that have banned abortion.
The temporary decision was made in a case brought by the Republican-led state of Louisiana, claiming the Food and Drug Administration, in adopting a 2023 rule - which allows Mifepristone to be dispensed through the mail - had ignored the risks of serious adverse events posed by the drug, including sepsis and haemorrhaging.
The panel ruled that Louisiana was likely to prevail in its challenge.
Danco, in its Supreme Court application, said the ruling "injects immediate confusion and upheaval into highly time-sensitive medical decisions—and it forces Danco, FDA, certified Mifeprex providers, patients, and pharmacies all to guess at what is allowed and what is not".
While that ruling is temporary, it is the first to significantly curtail access to Mifepristone in a series of lawsuits challenging the drug's initial approval in 2000 and subsequent rules making it easier to obtain.
The 2023 US Food and Drug Administration regulation removed a requirement that Mifepristone be dispensed in person.
In states where abortion is legal and doctors are permitted to prescribe drugs via telehealth, fewer than two per cent of prescriptions for abortion drugs are filled in person, according to research from the University of Southern California.
Drug companies GenBioPro and Danco Laboratories have intervened in Louisiana's lawsuit to defend the FDA regulation.
The brand-name version of Mifepristone, Mifeprex, is Danco's only product.
The Supreme Court in 2024 took up a challenge to the mail-order rule by medical groups and doctors, but ruled that they lacked legal standing to sue.
Missouri, Kansas and Idaho have taken over that case, which is pending.
US District Judge David Joseph in an April 7 decision, had paused Louisiana's lawsuit pending a review by President Donald Trump's administration of the safety of Mifepristone, which, according to media reports, has been delayed until after the November midterm elections.
The judge denied Louisiana's request to block the 2023 rule but agreed with the state that it was likely unlawful, indicating he would rule that way when the case resumes.
