Comparison of the effects of acetylsalicylic acid, ticlopidine and cilostazol on primary hemostasis using a quantitative bleeding time test apparatus.

We examined and compared the effects of aspirin (ASA), ticlopidine (TP) and cilostazol (CS) on bleeding time (BT) in 10 healthy adult male subjects using a newly developed quantitative bleeding time (QBT) test apparatus capable of simultaneously measuring total blood loss (Tv), maximum bleeding rate (Rmax), and bleeding pattern in addition to BT. All 3 drugs inhibited platelet aggregation response to ADP, collagen, epinephrine and arachidonic acid (p < 0.05), but not to ristocetin. Following oral administration of ASA (330 mg/day) or TP (300 mg/day) for 3 days, BT was significantly prolonged (mean BT increased from 359.3 to 646.0 s, p < 0.001, and from 323.3 to 528. 7 s, p < 0.01, respectively) and Tv was significantly increased (from 14.5 to 30.2 microl, p < 0.05, and from 12.5 to 19.2 microl, p < 0.01, respectively). Aspirin also increased Rmax (from 0.118 to 0. 159 microl/s, p < 0.05). The prolonged bleeding patterns after administration of ASA and TP were both type III, which has been reported to be less likely to lead to bleeding accidents. In contrast, none of these QBT parameters were altered by CS administration.