A conservative three-judge panel of the New Orleans-based 5th US Circuit Court of Appeals ruled unanimously that the Republican-led state of Louisiana was likely to prevail in its challenge to the 2023 rule adopted by Democratic former President Joe Biden's administration.
While Friday's 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.
The ruling was hailed by Louisiana's Republican Attorney General, Liz Murrill, who in a statement said she will "look forward to continuing to defend women and babies as this case continues."
The decision is not the final word on the issue, but is for now the most sweeping threat to abortion access since the Supreme Court rolled back abortion rights in 2022, said Kelly Baden, vice president at the Guttmacher Institute, an abortion rights advocacy group.
"Reimposing medically unnecessary in-person dispensing requirements for mifepristone will send shockwaves of chaos and confusion across the country and dramatically upend patients' ability to obtain abortion care," Baden said in a statement.
The FDA did not immediately respond to requests for comment.
Restricting access to mifepristone, including through telehealth appointments with out-of-state providers, has been a top priority for Republican-led states that have banned abortion, including Louisiana.
Nearly half of states have banned or severely restricted abortion since the US Supreme Court rolled back its recognition of a woman's constitutional right to the procedure in 2022. That has driven a surge in medication abortion, which has spurred a series of legal battles over access to the drugs.
Medication abortion is a two-drug regimen consisting of mifepristone, which is used in about two-thirds of US abortions, followed by misoprostol, used to terminate a pregnancy within the first 10 weeks.
In US 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.
Louisiana sued the FDA last year, claiming the agency in adopting the 2023 rule had ignored the risks of serious adverse events posed by mifepristone, including sepsis and haemorrhaging.
The Biden administration had maintained that mifepristone is effective and safe, citing studies that showed major adverse events occurring in fewer than one per cent of patients.
