Reference Range for Prothrombin Time-Coumadin
The optimal therapeutic ranges for the International Normalized Ratio (INR) for patients on oral anticoagulant therapy, according to the American College of Chest Physicians and the National Heart, Lung and Blood Institute (CHEST, volume 126 [supplement], page 204S, 2004), are shown below:
Post-surgical Prophylaxis of venous thromboembolism
(high-risk surgery) 2.0 - 3.0
Treatment of venous thrombosis 2.0 - 3.0
Treatment of pulmonary embolism 2.0 - 3.0
Tissue heart valves 2.0 - 3.0
Acute myocardial infarction (to prevent systemic embolism) 3.0 - 4.0
Valvular heartdisease 2.0 - 3.0
Atrial Fibrillation 2.0 - 3.0
Mechanical prosthetic valves (high risk) 2.5 - 3.5
Myocardial infarction (prevention of recurrence) 1.3 - 1.8
Note: The INR is intended for use only for monitoring the degree of anticoagulation in patients receiving oral coumarin derivates; most commonly Coumadin (warfarin).
Therapeutic LMWH Ranges
The optimal therapeutic ranges for LMWH will vary according to the drug. The measured peak anti-Xa activity varies among individual LMWH preparation given in the same anti-Xa dose due to variation in pharmacokinetics. The antiXa activity peaks at approximately 4 hours and this is the recommended time to perform monitoring assays if possible. Conservative therapeutic guidelines according to the American College of Chest Physidcians and the National Heart, Lung and Blood Institute (CHEST, volume 126 [supplement], page 204S, 2004) are shown below:
Enoxaparin (twice daily dosing for VTE) 0.6 - 1.0 anti-Xa units
Enoxaprain (once daily dosing for VTE) Not established
Tinzaparin (once a day) 0.85 mean anti-Xa units
Dalteparin (once a day) 1.05 mean anti-Xa units
Fonaparinux (once a day) Not established
Note: Pediatric dosing may be different than that for adults but data are lacking.
Therapeutic Direct Thrombin Inhibitors (DTI) Ranges
The optimal therapeutic ranges for the DTIs have not been established. Package insert therapeutic guideline suggests 1.5 - 3.0 times the baseline PTT.