The effect of diflunisal on hyaluronic acid production by ‘activated’ human synovial fibroblasts.

1 Cultured human synovial fibroblasts were ‘activated’ by leucocytes or poly (I) . poly (C) to overproduce hyaluronic acid. 2 Diflunisal in concentrations of 30, 15 and 10 microgram/ml completely abrogated the overproduction of hyaluronic acid induced by leucocytes. 3 Diflunisal (10 microgram/ml), indomethacin (2 microgram/ml) and aspirin (200 microgram/ml) partially inhibited the overproduction of hyaluronic acid induced by poly (I) . poly (C), although none of them decreased it to control non ‘activated’ levels. 4 Diflunisal 25 microgram/ml completely abrogated hyaluronic acid overproduction induced by poly (I) . poly (C). 5 This model could be an in vitro indicator for in vivo pharmacological levels of anti‐inflammatory drugs.