Hemostaseologic and hematologic parameters with aspirin and ticlopidine treatment in patients with cerebrovascular disease: a cross-over study.

No direct comparisons of the effects of ticlopidine and aspirin on platelet aggregability, clotting parameters, and blood count are available in a cross-over study design in humans. We investigated 45 patients with cerebrovascular disease. Twenty-one patients received 300 mg aspirin once daily for 2 weeks and then for 2 more weeks received 250 mg ticlopidine twice daily. In 24 other patients, the scheme was reversed. ADP-induced aggregability was lower during ticlopidine treatment; epinephrine- and collagen-induced aggregabilities were lower with aspirin treatment. Platelet counts were higher during ticlopidine than during aspirin treatment (199.6/ nl with aspirin, 213.0/nl with ticlop dine, p = 0.008), probably reflecting less platelet activation and degradation and a longer platelet survival time induced by ticlopidine treatment.