Thrombus formation in the carotid artery is one of the common causes of
transient ischemic attacks and
stroke. Platelet aggregation seems to be an essential component in these processes. The present study was conducted to determine the ability of
cilostazol, a
phosphodiesterase III inhibitor, to prevent formation of totally occlusive
thrombus in a porcine carotid artery, in comparison with
ticlopidine. Castrated male Yorkshire pigs were allocated to control (n=8),
cilostazol (30 mg/kg, twice a day [b.i.d] for 2 days, n=8), and
ticlopidine (50 mg/kg, b.i.d. for 3 days, n=7) groups. The endothelium of the right common carotid artery was injured with electrical stimulation (150 microA) without constriction and blood flow in this region was monitored by Doppler flow probe. Arterial blood was sampled during electrical stimulation for the measurement of platelet aggregation. Total occlusion rates within 240 minutes were 87.5% (7:8), 37.5% (3:8), and 85.7% (6:7) in the control,
cilostazol, and
ticlopidine groups, respectively. Compared with the control group, the time to total occlusion was significantly prolonged in the
cilostazol group, but not in the
ticlopidine group. Consistently, platelet aggregation was significantly inhibited only in the
cilostazol group. Because
ticlopidine increases blood flow in the intact carotid artery before injury to a greater extent than
cilostazol, direct antiplatelet action is thought to be responsible for
cilostazol's beneficial effect in preventing thrombotic occlusion. These results suggest that
cilostazol may be useful for the inhibition of the
thrombus formation in the carotid artery and for the prevention of cerebral ischemic events.