The influence of fenflumizole on platelet aggregation in patients with unstable angina pectoris.

We have studied the antiaggregatory effect of fenflumizole, a new non-steroidal antiinflammatory imidazole derivative, in ten patients with unstable angina pectoris. We have measured the aggregation induced by arachidonic acid (AA), ADP, and collagen, and serum or plasma concentrations of beta-thromboglobulin (beta-TG), platelet factor 4 (PF-4), thromboxane B2 (TXB2), and fenflumizole before, during, and after treatment with fenflumizole in two different regimens either as 10 mg b.i.d. for four days followed by 10 mg daily for six days (Group I, n = 5), or as 20 mg b.i.d. for four days followed by 20 mg daily for six days (Group II, n = 5). The threshold concentration of AA-induced platelet aggregation increased in both groups by the first day of treatment, the mean increase being significantly higher in Group II than in Group I. There was close correlation between serum fenflumizole and the threshold concentration of AA-induced platelet aggregation (r = 0.95). A significant fall in TXB2 occurred in both groups. In group I TXB2 concentrations subsequently increased to initial values during treatment, whereas it remained significantly reduced in Group II. There were no significant changes in collagen and ADP aggregation, and beta-TG and PF-4 concentrations remained unchanged during and after the administration of fenflumizole.