Intravenous magnesium does not influence the activity of the coagulation cascade.

Experimental arterial thrombus formation is reduced during intravenous magnesium infusion. It is well documented that magnesium reduces platelet reactivity, but the antithrombotic effect could also originate from anticoagulant properties or increased fibrinolysis. We therefore evaluated the effect of intravenous magnesium on prothrombin fragment 1 + 2 (F1 + 2), thrombin-antithrombin III complex (TAT) concentrations, and fibrin degradation products (FbDP) in a randomized, cross-over study in 14 healthy volunteers. Citrated blood samples were collected at 0, 30, and 180 min. An additional in vitro study on magnesium's effect on the activity of different coagulation factors was carried out. A transient increase was seen in F1 + 2 and TAT after 30 min but without any significant difference between the placebo and magnesium period. FbDP did not change significantly between the two treatments. Increasing concentrations of magnesium dose-dependently decreased binding of activated factor X to activated factor VII (FVIIa), but the decrease was slight and probably without any significance for coagulation at the concentrations tested. No effect was observed on the activity of FVIIa or activated factor VIII. In conclusion, no significant differences were observed on markers of coagulation or fibrinolytic activity during intravenous magnesium infusion. These results indicate that the observed antithrombotic effect of magnesium is more likely to arise from the previously observed platelet inhibition.