Less than three weeks after halting drug makers Mylan Inc. and Par Sterile Products from selling generic versions of Hospira Inc.’s blockbuster sedative Precedex, a judge in Baltimore performed an unexpected about-face on Friday that allows the generics to resume sales.

The decision by U.S. District Court Judge George Jarrod Hazel prompted an immediate appeal by Hospira and its lawyers at Venable, led by Paul Strain and Ralph Tyler. Hospira also filed an emergency motion for an injunction pending the outcome of its appeal, but on Monday the U.S. Court of Appeals for the Fourth Circuit denied the request.