Warfarin therapy

The nurse monitors the prothrombin time (PT) during therapy. Optimal PT for warfarin therapy is... 

Either UFH or LMWH should be administered to patients with NSTE ACS. Therapy should be continued for up to 48 hours or until the end of the angiography or PCI procedure. In patients initiating warfarin therapy, UFH or LMWHs should be continued until the International Normalized Ratio (INR) with warfarin is in the therapeutic range for 2 consecutive days. The addition of UFH to aspirin reduces the rate of death or MI in patients with NSTE ACS.47 Enoxaparin was mentioned as preferred over UFH in the 2002 ACC/AHA clinical practice guidelines, as two large clinical trials found a reduction in the combined endpoint of death, MI, or need for PCI in patients... 

The majority of patients with AF should receive warfarin therapy (titrated to an International Normalized Ratio of 2 to 3) for stroke prevention, particularly if they have other risk factors for stroke. 

Stroke Prevention All patients with paroxysmal, persistent, or permanent AF should receive therapy for stroke prevention, unless compelling contraindications exist. A decision strategy for stroke prevention in AF is presented in Fig. 6-9.27 In general, most patients require therapy with warfarin in some patients with no additional risk factors for stroke, aspirin may be acceptable. For some patients, serious consideration of the benefits of warfarin versus the risks of bleeding associated with warfarin therapy is warranted. The potential bleeding risks associated with warfarin may outweigh the benefits in... 

Provide information regarding safe and effective warfarin therapy ... 

FIGURE 7-9. Initiation of warfarin therapy. INR, International Normalized Ratio PT, prothrombin time. (Reproduced from Haines ST, Zeolla M, Witt DM. Venous thromboembolism. In DiPiro JT, Talbert RL, Yee GC, et al, (eds.) Pharmacotherapy A Pathophysiologic Approach. 6th ed. New York McGraw-Hill 2005 391, with permission.)... 

Continue warfarin therapy for an appropriate duration based on the presence of ongoing risk factors. 

How will you manage BA s warfarin therapy Outline a plan including specific dose changes, timing of monitoring, and patient education. 

First episode of idiopathic VTE with or without a documented hypercoagulable abnormality Warfarin 12 Continue warfarin therapy after 12 months if patient is at low risk for bleeding... 

Inform patient about the effects of vitamin K-rich foods on warfarin therapy. Moderate intake (less than 500 to 1000 meg) of vitamin K is acceptable. Provide patient with written material regarding vitamin K content of foods. 

Inform the patient about the potential drug-drug interactions with warfarin, including over-the-counter medications and dietary supplements (Tables 7-8, 7-9, and 7-10). Instruct the patient to call the health care practitioner responsible for monitoring warfarin therapy before starting any new medications or dietary supplements. 

Re-evaluate the risks and benefits of continuing warfarin therapy. 

Disulfiram inhibits several of the enzymes responsible for warfarin metabolism increased PT/INR have been noted if disulfiram is added to warfarin therapy, carefully monitor PT/INR the warfarin dose will probably have to be decreased. 

The water-soluble and fat-soluble vitamins in the parenteral multivitamin mix are essential cofactors for numerous biochemical reactions and metabolic processes. Parenteral multivitamins are added daily to the PN. Patients with chronic renal failure are at risk for vitamin A accumulation and potential toxicity. Serum vitamin A concentrations should be measured in patients with renal failure when vitamin A accumulation is a concern. Previously, vitamin K was administered either daily or once weekly because intravenous multivitamin formulations did not contain vitamin K. However, manufacturers have reformulated their parenteral multivitamin products to provide 150 meg of vitamin K in accordance with FDA recommendations. There is a parenteral multivitamin formulation available without vitamin K (e.g., for patients who require warfarin therapy), but standard compounding of PN formulations should include a parenteral multivitamin that contains vitamin K unless otherwise clinically indicated. 

The most commonly used oral anticoagulant drug in the U.S. is warfarin. It acts by altering vitamin K so that it is unavailable to participate in synthesis of vitamin K-dependent coagulation factors in the liver (coagulation factors II, VII, IX, and X). Because of the presence of preformed clotting factors in the blood, the full antithrombotic effect of warfarin therapy may require 36 to 72 h. 

Tab. 4.1 Known causes of individual variability in warfarin therapy in thromboembolism...

In patients initiating warfarin therapy, UFH or LMWHs should be continued until the international normalized ratio with warfarin is in the therapeutic range. 

Warfarin should begin concurrently with UFH or LMWH therapy. For patients with acute VTE, heparin and warfarin therapy should be overlapped for at least 4 to 5 days, regardless of whether the target INR has been achieved earlier. The UFH or LMWH can then be discontinued once the INR is within the desired range for 2 consecutive days. 

Guidelines for initiating warfarin therapy are given in Fig. 14-3. The usual initial dose is 5 to 10 mg. In older patients (age >60 years) and those taking potentially interacting medications, a starting dose of 2.5 mg should be considered. 

FIGURE 14-3. Initiation of warfarin therapy. (INR, international normalized ratio PT, prothrombin time.)... 

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