CHANGES IN PLATELET BEHAVIOUR DURING ARVIN THERAPY

In seven patients treated with ' Arvin ', a purified coagulant fraction of Malayan pit-viper venom, changes in platelet aggregation in response to adenosine diphosphate were studied. In all patients platelet aggregation was reduced in the first 24 hours of therapy. In the later stages of therapy, aggregation tended to return to the pretreatment values. The level of circulating fibrinogen-degradation products rose to high levels in the early stages of therapy, and a positive correlation was found between these degradation products and the extent of the inhibition of platelet aggregation. In four of the seven patients the greatest inhibition of aggregation happened at the time when the fibrinogen-degradation products were at their peak concentration. It is suggested that fibrinogen-degradation products may have been mainly responsible for the decrease in platelet aggregation. This impaired platelet aggregation may be important in the maintenance of vascular patency during arvin therapy.