Intravenous magnesium does not influence the activity of the coagulation cascade

Experimental arterial thrombus formation is reduced during intravenous magn esium infusion. It is well documented that magnesium reduces platelet react ivity, but the antithrombotic effect could also originate from anticoagulan t properties or increased fibrinolysis. We therefore evaluated the effect o f intravenous magnesium on prothrombin fragment 1+2 (F1+2), thrombin-antith rombin III complex (TAT) concentrations, and fibrin degradation products (F bDP) in a randomized, cross-over study in 14 healthy volunteers. Citrated b lood samples were collected at 0, 30, and 180 min. An additional in vitro s tudy 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 mi n but without any significant difference between the placebo and magnesium period. FbDP did not change significantly between the two treatments. Incre asing concentrations of magnesium dose-dependently decreased binding of act ivated factor X to activated factor VII (FVIIa), but the decrease was sligh t and probably without any significance for coagulation at the concentratio ns tested. No effect was observed on the activity of FVIIa or activated fac tor VIII. In conclusion, no significant differences were observed on marker s of coagulation or fibrinolytic activity during intravenous magnesium infu sion. These results indicate that the observed antithrombotic effect of mag nesium is more likely to arise from the previously observed platelet inhibi tion. (C) 2001 Lippincott Williams & Wilkins.