Inhibitory activity of indobufen (*) on platelet aggregation in vivo

Indobufen, administered by gavage, reduced mortality induced in mice and rabbits by intravenous injection of arachidonic acid (A.A.). The doses of compound required to protect 50% of the mice and rabbits from death (ED50) were 1.3 and 0.58 mg/kg respectively. Acetylsalicylic acid (ASA) was considerably less active than indobufen (ED50 = 22.4 and 8 mg/kg). Since the lethal effect of A.A. is mostly due to the formation of platelet aggregates (Silver et al., 1974; Kohler et al., 1976), it is concluded that indobufen is a very potent inhibitor of platelet aggregation in vivo.