Terbogrel is an orally available thromboxane A2 receptor antagonist and a thromboxane A2 synthase inhibitor, with both IC50s of about 10 nM. Pretreatment of platelets with terbogrel 1 μM completely inhibits thrombin-induced thromboxane A2 formation (2±1 ng/mL) but does not result in any inhibition of platelet aggregation. Terbogrel (1 μM) completely inhibits U46619-induced platelet aggregation, and the IC50 value is 10 nM. Terbogrel inhibits both platelet aggregation and thromboxane A2 formation with an IC50 of about 10 nM. Terbogrel inhibits the thromboxane A2 synthase in human gel-filtered platelets with an IC50 value of 4.0 ± 0.5 nM. Terbogrel blocks the thromboxane A2/endoperoxide receptor on washed human platelets with an IC50 of 11 ± 6 nM (n = 2) and with an IC50 of 38 ± 1 nM (n = 15) in platelet-rich plasma. Terbogrel inhibits the collagen-induced platelet aggregation in human platelet-rich plasma and whole blood with an IC50 of 310 ± 18 nM (n = 8) and 52 ± 20 nM (n = 6), respectively. Terbogrel (0.1-3.0 mg/kg) demonstrates an impressive antithrombotic efficacy in rabbits. Terbogrel (10 mg/kg, po) is rapidly and well (90%) absorbed with a systemic availability of about 30% in rats.