Nimesulide is classed as a fast-acting non-steroidal anti-inflammatory drug (NSAID). It's sold widely across Europe, Latin America and Asia as a prescription-only anti-inflammatory - but not in the US, due to concerns about liver damage.

It's marketed under the brand names Coxta, Eskaflam, Octaprin, Nimside, Nise, Nilsid, Drexel, Donulide, Nimutab, Novolid, Relmex and many others ref

It was discovered in 1971, but its mechanism of action has not yet been properly described.

Nimesulide effects are unique and not shared with other selective COX-2 inhibitors. On the inflammatory process, the efficacy of nimesulide is dependent upon a wide spectrum of actions, due to the combination of effects on immune and non–immune cells, resident cells and extracellular matrix with a biochemical mechanism that has not been elucidated at all, but there is much evidence that it goes beyond COX-2 inhibition

See The relatively selective cyclooxygenase-2 inhibitor nimesulide: What’s going on? European Journal of Pharmacology, Volume 848, 5 April 2019, Pages 105-111