Magnesium inhibits arterial thrombi after vascular injury in rat: In vivo impairment of coagulation

Magnesium deficiency is associated with a high frequency of cardiac arrhyth mia, hypertension and sudden ischemic death. We investigated the in vivo ef fects of intravenous magnesium administration in a rat model of chemically induced (FeCl3) carotid thrombosis. The infusion of magnesium sulfate (MgSO 4) before the topical application of FeCl3 prevented thrombus formation at concentrations of 0.3 M and 0.6 M, and delayed it even at 0.15 M. Similar r esults were obtained with MgCl2. The infusion of MgSO4 0.6 M seven minutes after FeCl3 appli- cation delayed but did not prevent thrombus formation. M gSO4 slightly reduced platelet aggregation ex vivo without affecting plasma clotting tests, but in vivo blood clotting time was markedly prolonged (ta il! transection method), thus indicating profoundly impaired coagulation. T hese data provide a rationale for the use of magnesium as an anti-thromboti c agent, but its pharmacological effect critically depends on the timing of administration.