An anti-inflammatory was a type of drug that reduced inflammation.
In 2368, Doctor Beverly Crusher gave Soren something to reduce the inflammation caused by a concussion the J'naii pilot had suffered. (TNG: "The Outcast")
In 2374, Tuvok suggested that Neelix ask The Doctor for an anti-inflammatory in lieu of multiple pillows, without which the Talaxian claimed he had terrible neck pains. (VOY: "Demon")