Effects of long-term ticlopidine treatment on platelet function and its tolerability in cerebrovascular disease

Long Term Prognosis in Patients with Peripheral Arterial Disease Treated with Antiplatelet Agents

OBJECTIVE

To determine the fatal and non-fatal cardiovascular event rate in patients with intermittent claudication treated with antiplatelet agents.

METHODS AND DESIGN

Patients with PAD-II stage Fontaine (n=223) and sex and age matched controls (n=446) were followed up from 1974 to 1998. All patients were treated with antiplatelet agents (aspirin, 325 mg once daily or ticlopidine, 250 mg twice daily) and for risk factors, if present. The end points were death for any cause (vascular event, cancer, and others) and non-fatal vascular events (myocardial infarction, ischemic/hemorrhagic stroke, and leg amputation).

RESULTS

PAD patients had a significantly higher mortality rate than controls (3.99 vs. 2.53 deaths for 100 patients per year, respectively), cancer (mostly lung, stomach and colon) and vascular mortality accounted for such difference. The incidence of non-fatal vascular events was three times higher in patients than in controls (1.7 vs. 0.56, 100 patients per year, respectively, p<0.05) even considering amputation separately (0.28 vs. 0.00, 100 patients per year, p<0.05). No difference between patients treated with aspirin or ticlopidine could be found in both end points.

CONCLUSIONS

Vascular mortality and morbidity, despite the use of antiplatelet agents, are still higher than sex and age matched controls; however, the commonest cause of death is cancer.

Effect of plasma fibrinogen concentration on the inhibition of platelet aggregation after ticlopidine compared with aspirin

BACKGROUND AND PURPOSE

Elevated levels of plasma fibrinogen are a risk factor for cerebral infarction. Because fibrinogen plays a central role in platelet aggregation and binding of fibrinogen to platelets is inhibited by ticlopidine, we studied the effect of the plasma fibrinogen concentration on the antiaggregatory action of ticlopidine compared with that of aspirin.

METHODS

We determined platelet aggregability before and after administration of ticlopidine (200 mg/d) or aspirin (81 mg/d) in 61 stroke patients and correlated the changes with the plasma fibrinogen concentration.

RESULTS

In patients receiving ticlopidine, the platelet aggregability induced by 1, 5, and 10 mumol/L adenosine diphosphate significantly decreased compared with aggregability before medication (P < .05), and the reductions had significant negative correlations with the plasma fibrinogen concentration (P < .05). In patients receiving aspirin, the platelet aggregability induced by 2 micrograms/mL collagen and 5 and 10 mumol/L adenosine diphosphate decreased compared with aggregability before medication (P < .005), but the reductions had no significant correlation with the plasma fibrinogen concentration.

CONCLUSIONS

The relative antiaggregatory effect of ticlopidine is significantly decreased with higher plasma fibrinogen concentrations. This may explain, at least in part, the individual variation in the response to ticlopidine.

How does ticlopidine treatment lower plasma fibrinogen?

Many clinical studies have evaluated the clinical efficiency of ticlopidine in vascular pathology and in few of these studies the plasma Fg level was determined as a biological parameter and not a primary end point. All these studies are heterogeneous because plasma Fg concentration have been measured using various methods, patients were included at various time after the acute event and were followed over a period of 1 to 24 months of treatment with ticlopidine, patients suffered from various pathology: peripheral arterial disease, cerebrovascular disease, diabetes or polycythemia vera. Despite the heterogeneity of these prospective studies, a general trend indicates a decrease in the plasma Fg levels by 10 to 25% with ticlopidine compared to placebo. This decrease in circulating Fg was associated with clinical improvement, and, when studied, hemorheological modifications (decreases in whole blood and plasma viscosities). The mechanism of ticlopidine action is discussed.