The first- and second-generation antipsychotic drugs affect ADP-induced platelet aggregation.

OBJECTIVE

Blood platelets play an important role in haemostasis and their hyperaggregability may lead to thrombosis and cardiovascular diseases. Increased incidence of mortality, caused by cardiovascular disease, and the increased risk of thrombotic complication in schizophrenic patients treated with antipsychotics have been reported. The effects of antipsychotic drugs on blood platelet function are not fully explained, therefore the purpose of the present study was to examine and compare the effects of the second-generation antipsychotic drugs used in schizophrenia (clozapine, risperidone and olanzapine), with the effects of the first generation antipsychotic, haloperidol, on the platelet aggregation induced by ADP in vitro.

METHODS

Blood obtained from healthy volunteers (n=25) collected into sodium citrate was centrifuged (250xg, 10 min) at room temperature to obtain platelet-rich plasma. Aggregation of blood platelets (10 microM ADP) was recorded (Chrono-log aggregometer) in platelet-rich plasma preincubated with antipsychotic drugs (final concentration: clozapine 420 ng/ml, risperidone 65 ng/ml, olanzapine 40 ng/ml, haloperidol 20 ng/ml) for 30 min.

RESULTS

Our results showed that all tested drugs inhibit platelet aggregation induced by ADP in vitro. Among studied antipsychotic drugs clozapine and olanzapine significantly reduced platelet aggregability in vitro. In comparison with control platelets (without the drug), clozapine inhibited ADP-induced platelet aggregation by 21% (P=3.7x10(-6)) and olanzapine by 18% (P=2.8x10(-4)), respectively.

CONCLUSION

The obtained results indicate that antipsychotic drugs, especially clozapine and olanzapine, contrary to haloperidol, reduced response of blood platelets to ADP measured as platelet aggregation. This suggests that therapy with such antipsychotics, particularly with second-generation antipsychotics, may partly reduce prothrombotic events associated with the increased platelet activation observed in schizophrenic patients. The mechanism of antiaggregatory influence of antipsychotics requires further studies.