Standard unfractionated heparin (UFH) has long been used to prevent death and myocardial infarction in patients with acute coronary syndrome and acute occlusion undergoing percutaneous revascularization. However, UFH binds to several plasma proteins, platelets, and endothelial cells producing a highly variable anticoagulant response. In contrast, Low molecular weight heparin (LMWH) exhibits less protein binding and provides more predictable anticoagulant response with reduced need for patient monitoring and dosage adjustment. The purpose of this study was to assess the anti-Xa activities of LMWH in Korean patients with acute coronary syndrome after recommended dose for caucasians and to determine an optimal method of administration of LMWH.

Twenty five patients with acute coronary syndrome were enrolled and allocated to five separate groups (5 patients in each group) by types according to molecular weight (LMWH (A): (molecular weight of 4500 daltons, LMWH (B): molecular weight of 6400 daltons) and methods of administration (Group 1A and 1B: Subcutaneous and subcutaneous injections (SC-SC), Group 2: Intravenous and subcutaneous injections (IV-SC), Group 3A and 3B: Intravenous, subcutaneous and subcutaneous injections (IV-SC-SC). Five groups were as follows: Group 1A: LMWH (A) 1 mg/kg SC every 12 hours, Group 1B: LMWH (B) 100 IU/kg SC every 12 hours, Group 2: LMWH (A) 1 mg/kg IV bolus and 1 mg/kg SC 12 hours later, Group 3A: LMWH (A) 0.5 mg/kg IV bolus, 3 hours later 1 mg/kg SC every 12 hours, Group 3B: LMWH (B) 50 IU/kg IV bolus, 3 hours later 100 IU/kg SC every 12 hours. Anti-Xa activity was measured by amidolytic assay method (Rotachrome, Stago, France) in 555 samples from 25 patients. All the data of anti-Xa activity in each group were plotted along the sequential time and mean values of them were analyzed by Wilcoxon signed rank test.

1)The anti-Xa activity (mean 0.6216±0.238 IU/mL) of LMWH (A) was greater than that of LMWH (B)(mean 0.2587±0.1709 IU/mL) in the conventional SC-SC method (p<0.001). 2) The anti-Xa activity of LMWH (A) (mean 0.6203±0.2383 IU/mL) was also greater than that of LMWH (B)(mean 0.468±0.2428 IU/mL) in the IV-SC-SC method (p<0.001). 3) More rapid and effective anti-Xa activities were achieved by IV-SC-SC method compared with conventional SC-SC method.

This study suggests that immediate achievement and optimum maintenance of anticoagulant activity can be accomplished by IV-SC-SC method rather than conventional SC-SC method in patients of acute coronary syndrome.