View source for Warfarin

====Empiric dosing====
On first look, the evidence table suggests that the Harrison 5 mg algorithm from Hamilton is the chest combination of efficacy and safety; however, two independent studies (Kovacs<ref name="pmid12729425"/> and Quiroz in 2006 from the Massachusetts General Hospital<ref name="pmid16893712"/>) have not been able to replicate the results of Hamilton group of Harrison and Crowther. One explanation may be that the personnel in the Harrison study were more expert and the flexibility in the algorithm allowed expression of their expertise. If so, then perhaps equally expert health care providers should use the Harrison 5 mg algorithm while other personnel should use the Kovacs 10 mg algorithm. Considering that the expertise of the Massachusetts General Hospital could not replicate the Hamilton results, perhaps most providers should use the Kovacs 10 mg algorithm, at least for inpatients.

A [[systematic review]] of the [[randomized controlled trial]]s done through 2003 of 5 mg versus the 10 mg concluded that the Kovacs 10 mg regimen is best.<ref name="pmid15522981"/> This conclusion was largely based on the inability of the results of the Harrison 5 mg flexible algorithm to be replicated by Kovacs.

[[Clinical practice guideline]]s in 2004 by the [[American College of Chest Physicians]] concluded that either 5 or 10 loads are acceptable.<ref name="pmid15383473">{{cite journal |author=Ansell J ''et al.'' |title=The pharmacology and management of the vitamin K antagonists: the Seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy |journal=Chest |volume=126 |issue=3 Suppl |pages=204S–33S |year=2004 |pmid=15383473 }}</ref> The guidelines also state "if treatment is not urgent (eg, chronic stable atrial fibrillation), warfarin administration, without concurrent heparin administration, can be commenced out-of-hospital with an anticipated maintenance dose of 4 to 5 mg per day."<ref name="pmid15383473"/>

Since publication of the [[systematic review]]<ref name="pmid15522981"/> and [[clinical practice guideline]]s<ref name="pmid15383473"/>, a nonblinded, [[randomized controlled trial]]<ref name="pmid21035980">{{cite journal| author=Farahmand S, Saeedi M, Seyed Javadi HH, Khashayar P| title=High doses of warfarin are more beneficial than its low doses in patients with deep vein thrombosis. | journal=Am J Emerg Med | year= 2011 | volume= 29 | issue= 9 | pages= 1222-6 | pmid=21035980 | doi=10.1016/j.ajem.2010.07.008 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=21035980  }} </ref> found no difference between algorithms, but also achieved less frequent anticoagulation. The reason is not clear as the Kovacs 10 mg algorithm is very specific on each dose of warfarin. The last trial is also unique in that all patients were receiving a fondaparinux bridge.

'''Additional algorithms:'''<br>
* The Tait 5 mg regimen is for outpatient anticoagulation. Patients are given 5 mg of warfarin per day for 5 days and then the INR is checked on day 5 to determine further dosing. ([http://www.blackwell-synergy.com/action/showPopup?citid=citart1&id=f1&doi=10.1046%2Fj.1365-2141.1998.00716.x summary])<ref name="pmid9633885">{{cite journal |author=Tait RC, Sefcick A |title=A warfarin induction regimen for out-patient anticoagulation in patients with atrial fibrillation |journal=Br. J. Haematol. |volume=101 |issue=3 |pages=450-4 |year=1998 |pmid=9633885 |doi=10.1046/j.1365-2141.1998.00716.x}}</ref>
* The Fennerty 10 mg regimen is an older regimen that has not been studied in an [[randomized controlled trial]].<ref name="pmid6424820">{{cite journal |author=Fennerty A ''et al.'' |title=Flexible induction dose regimen for warfarin and prediction of maintenance dose |journal=Br Med J (Clin Res Ed) |volume=288 |pages=1268–70 |year=1984 |pmid=6424820 }} [[http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=citizendium&pubmedid=6424820 PubMed Central]]</ref><ref name="pmid3144365">{{cite journal |author=Fennerty A ''et al.''  |title=Anticoagulants in venous thromboembolism |journal=BMJ |volume=297 |issue=6659 |pages=1285-8 |year=1988 |pmid=3144365}}</ref>