Warfarin anticoagulants

Prothrombin time PT is performed by adding thromboplastin (tissue) factor and calcium to citrate-anticoagulated plasma, recalcifying the plasma, and measuring the clotting time. The major utility of PT is to measure the activity of the vitamin K-dependent factors II, VII, and X. The PT is used in evaluation of liver disease, to monitor warfarin anticoagulant effect, and to assess vitamin K deficiency. 

Fasco M. J., Hildebrandt E. F Suttie J. W. Evidence that warfarin anticoagulant action involves two distinct reductase activities. J Biol Chem 1982 257, 11210-2. 

Selected patients also should be treated with long-term warfarin anticoagulation. 

No need to adjust INR in warfarin anticoagulated patients with topical hemostatic mouthwash use... 

Middlekauff, H.R., Stevenson, W.G., Gombein, J.A. (1995). Anti-arrhythmic prophylaxis vs warfarin anticoagulation to prevent thromboembolic events among patients with atrial fibrillation. A decision analysis. Arch. Intern. Med. 155(9) 913-20. 

E Kramer, M, Tsuru, C. E. Cook, C. J. McClain, and J. L. Holtzman, Effect of influenza vaccine on warfarin anticoagulation, Clin. Pharmacol. Therap., 35 416-418 (1984). 

There was a rise in INR from 2.8 to 12 when a topical pain-relieving gel containing methylsalicylate was applied to the knees of a 22-year-old white woman taking stable warfarin anticoagulation (274). 

Zacharski LR, Henderson WG, Rickies FR, Forman WB, Cornell CJ Jr, Forcier RJ, Edwards RL, Headley E, Kim SH, O Donnell JF, et al. Effect of warfarin anticoagulation on survival in carcinoma of the lung, colon, head and neck, and prostate. Final report of VA Cooperative Study 75. Cancer 1984 53(10) 2046-52. 

Zauber NP, Stark MW. Successful warfarin anticoagulation despite protein C deficiency and a history of warfarin necrosis. Ann Intern Med I986 I04(5) 659-60. 

Hamer A, Peter T, Mandel WJ, Scheinman MM, Weiss D. The potentiation of warfarin anticoagulation by amiodarone. Circulation 1982 65(5) 1025-9. 

Hylek EM, Heiman H, Skates SJ, Sheehan M A, Singer DE. Acetaminophen and other risk factors for excessive warfarin anticoagulation. JAMA 1998 279(9) 657-62. 

Sioris LJ, Weibert RT, Pentel PR. Potentiation of warfarin anticoagulation by sulfisoxazole. Arch Intern Med 1980 140(4) 546-7. 

Grebe HB, Gregory PJ. Inhibition of warfarin anticoagulation associated with chelation therapy. Pharmacotherapy 2002 22(8) 1067-9. 

Gomohn IH, Chapron DJ, Luhan PA. Lack of effect of influenza vaccine on theophylUne levels and warfarin anticoagulation in the elderly. J Am Geriatr Soc 1985 33(4) 269-72. 

However, in a case-control study of the risk factors for excessive warfarin anticoagulation the investigators studied 289 patients prospectively, 93 with an International Normalized Ratio (INR) over 6.0 and 196 with an INR of 1.7-3.3 during warfarin therapy (125). Paracetamol intake was independently associated with a high INR and the effect was dose-related. At a dosage of about 2-4 g/week the adjusted odds ratio (OR) for having an INR over 6 was 3.5 (95% Cl = 1.2, 10) compared with no intake of paracetamol. At an intake of 4-9 g/week the adjusted OR was 6.9 (95% Cl = 2.2, 22), and at an intake over 10 g/week the OR was 10 (95% Cl = 2.6, 38). 

Contraindications Patients taking warfarin (anticoagulant) should have their PT monitored closely. Iron and E should not be taken together because iron can interfere with the body s absorption and use of vitamin E. 

Pubentz, M.J. Calcagno, D.E. Teeters, J.L. Improving warfarin anticoagulation therapy in a community health system. Pharm. Pract. Manage. Q. 1998, 18 (3), 1-16. 

Wallis DE, Quintos R, Wehrmacher W, Messmore H. Safety of warfarin anticoagulation in patients with heparin-induced thrombocytopenia. Chest 1999 116 1333-1338. 

Fresh frozen plasma contains the components of the coagulation system and is indicated for the replacement of deficient coagulation factors II, V, VII, X, XI, and XIII. Factor VIII and IX deficiencies are treated with specific factor concentrates. Fresh frozen plasma is also used for the rapid reversal of warfarin anticoagulation and in the treatment of disseminated intravascular coagulation. Thrombotic thrombocytopenic purpura is treated by means of therapeutic plasma exchange with fresh frozen plasma as the replacement fluid. Cryo-precipitate, which contains factor VIII, von Willebrand s factor, and fibrinogen, is indicated for the treatment of von Willebrand s disease that does not respond to desmopressin acetate, and for fibrinogen replacement (see Chap. 100). 

Cimetidine, a drug used to treat stomach ulcers, can inhibit the metabolism of several potentially toxic drugs such as phenytoin (antiepileptic), warfarin (anticoagulant) and theophylline (bronchodilator). 

Sulphonamides interact with warfarin (anticoagulant) and sulphonylureas (oral hypo-glycaemics) by enhancing the actions of these drugs. 

Angaran DM, Dias VC, Arom KV, Northrup WF, Kersten TE, Lindsay WG, Nicoloff DM. The influence of prophylactic antibiotics on Ae warfarin anticoagulation response in die postoperative prosthetic cardiac valve patient. Ann Surg (1984) 199, 107-111,... 

Hall G, Lind MJ, Huang M, Moore A, Gane A, Roberts JT, Cantwell BMJ, Intravenous infusions of ifosfamide/mesna and perturbation of warfarin anticoagulant control, PostgradMed... 

Ariyaratnam, Thakker NS, Sloan P, Thornhill MH Potentiatiai of warfarin anticoagulant activity by miconazole oral gel. BW 99T) 314,349... 

Pemberton MN, Sloan P, Ariyaratnam S, Thakker NS, Thcxnhill MH. Derai ement of warfarin anticoagulation by micCTiazole oral gel. BrDent J (1998) 184,68-9. 

Zhou S, Chan E. Effect of ubidecarenone on warfarin anticoagulation and phaimacckinetics of warfarin enanticxneiB in mts. Drug Metabol Drug Interact (200V) 18,99-122. 

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