A comparative study of the effects of local anaesthetics on platelet aggregation.

A variety of drugs that are generally thought to modify biological membrane action may affect platelet function [ 11. Phospholipase A? is a membrane-bound enzyme, and plays a key role in the release of arachidonic acid from platelet membrane phospholipids [ 21. The arachidonic acid thus released is converted by platelet cyclo-oxygenase and lipoxygenase pathways to prostaglandin endoperoxides, thromboxane A: and hydroperoxyeicosatetraenoic acid, resulting in platelet aggregation. In the present investigation we sought to evaluate the effect of local anaesthetic agents (thought to act by stabilizing membrane) o n platelet aggregation induced by various aggregating agents. Blood was taken by venepuncture from normal human volunteers reported t o be free of medication for 1 week. Blood samples were mixed with 3.8% (w/v) sodium citrate solution (9: 1 ) and centrifuged at 260 g for 15 min at 20°C to obtain platelet-rich plasma. The remaining blood sample was centrifuged at 1200 g for 10 min to obtain platelet-poor plasma. Platelet count was determined by phase-contrast microscopy and all aggregation studies were carried out at 37°C with platelet-rich plasma having platelet counts between 2.5 and 3.0 x 1Ox/ml of plasma. Aggregation was monitored with a Dual-channel Lumi-aggregometer (model 400, Chronolog Corporation, Chicago, IL, U.S.A.) using 0.45 ml aliquots of platelet-rich plasma. The final volume was made up to 5 ml with sodium chloride (0.9’/0, w/v) or test drug and incubated for 1 min before challenge with the