Warfarin administration and monitoring
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
The optimal dose of warfarin among patients on chronic anticoagulation represents a balance between the highest thrombosis prevention and the lowest risk of bleeding. In order to optimize the efficacy to safety ratio, dosing of warfarin requires INR monitoring with a target INR range of 2-3. The 2012 American College of Chest Physicians (ACCP) clinical practice guidelines "suggest using validated decision support tools (paper nomograms or computerized dosing programs) rather than no decision support (Grade 2C)."[1] Current recommendations on chronic warfarin management are mainly based on the RE-LY trial[2] which was published in 2009 with modifications due to subsequent practice guidelines by the American College of Chest Physicians in 2012.[1]
Adjustment of Warfarin Dose According to INR
INR Value | Response per RE-LY[2] | Alternative by ACCP[1] |
---|---|---|
≤ 1.5 | ↑ weekly dose by 15% | Patients with stable INRs at baseline, now with a single subtherapeutic INR value: no routine bridging with heparin |
1.51-1.99 | ≤1.5: ↑ weekly dose by 10% | Patients with stable INRs at baseline, now with a single out-of-range INR of < 0.5 below or above therapeutic: no change and retest 1-2 weeks |
2-3 | No dose adjustment | |
3.01 - 4 | ↓ weekly dose by 10% | Patients with stable INRs at baseline, now with a single out-of-range INR of < 0.5 below or above therapeutic: no change and retest 1-2 weeks |
4.01 - 4.99 | Hold dose for 1 day, then ↓ weekly dose by 10% | Patients with INRs 4.5 - 10 and with no evidence of bleeding: ACCP suggests against the routine use of vitamin K |
5 - 8.99 | Hold dose until INR therapeutic, then ↓ weekly dose by 15% | |
≥ 9.0 | Hold warfarin and give vitamin K 5.0-10mg PO. Monitor more frequently and repeat vitamin K if necessary | Patients with INRs > 10.0 with no evidence of bleeding: ACCP suggests that oral vitamin K be administered |
Based on the existing medical research and clinical practice guidelines, institutions have algorithms to standardize the chronic administration of warfarin. For instance, the RE-LY and ACCP guidelines have been combined by the Department of Internal Medicine at KUSM-W and is located at Warfarin by Wichita.
Pill selection
Recommendations exist for consistent use of one pill size by anticoagulation clinics.[3] The importance of choice of pill size is not clear.[4][5]
Management of Warfarin Related Bleeding
The management of bleeding among patients on warfarin includes:[1]
- Rapid reversal of anticoagulation with the administration of four-factor prothrombin complex concentrate (PCC), PLUS
- Slow IV injection of 5 to 10 mg vitamin K
References
- ↑ 1.0 1.1 1.2 1.3 Holbrook A, Schulman S, Witt DM, Vandvik PO, Fish J, Kovacs MJ; et al. (2012). "Evidence-based management of anticoagulant therapy: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines". Chest. 141 (2 Suppl): e152S–84S. doi:10.1378/chest.11-2295. PMC 3278055. PMID 22315259.
- ↑ 2.0 2.1 Connolly SJ, Ezekowitz MD, Yusuf S, Eikelboom J, Oldgren J, Parekh A; et al. (2009). "Dabigatran versus warfarin in patients with atrial fibrillation". N Engl J Med. 361 (12): 1139–51. doi:10.1056/NEJMoa0905561. PMID 19717844. Review in: Ann Intern Med. 2010 Jan 19;152(2):JC1-2
- ↑ Ebell MH (2005). "Evidence-based adjustment of warfarin (Coumadin) doses". Am Fam Physician. 71 (10): 1979–82. PMID 15926414.
- ↑ Wong W, Wilson Norton J, Wittkowsky AK (1999). "Influence of warfarin regimen type on clinical and monitoring outcomes in stable patients in an anticoagulation management services". Pharmacotherapy. 19 (12): 1385–91. PMID 10600087.
- ↑ Manning DM (2002). "Toward safer warfarin therapy: does precise daily dosing improve international normalized ratio control?". Mayo Clin Proc. 77 (8): 873–5. doi:10.4065/77.8.873-a. PMID 12173723.