Effect of sulphinpyrazone on human platelet aggregation, 5-hydroxytryptamine release and adhesion ex vivo: comparison with naproxen.

1 The effects of single doses of naproxen and sulphinpyrazone and of 4 and 8 days treatment with sulphinpyrazone on human platelet responsiveness were compared. 2 A single dose of sulphinpyrazone had no effect whereas a single dose of naproxen caused a five-fold depression in responsiveness to collagen. 3 Repeated administration of sulphinpyrazone led to a weak and equivocal inhibitory effect on collagen-induced aggregation, second phase aggregation in response to ADP and adhesion to collagen. There was no effect on ADP-induced first phase aggregation, adrenaline-induced second phase aggregation or platelet retention in glass bead columns. 4 It is concluded that the anti-aggregant activity of sulphinpyrazone is too weak to be a major factor in its reported effect on the incidence of cardiac death.