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CHAPTER AIMS
The aims of this chapter are to:
Discuss the roles of clinical reasoning and critical thinking skills in each step of the Pharmacists’ Patient Care Process (PPCP) to assess and resolve warfarin management-related problems.
Describe elements of clinical reasoning and critical thinking applied to the PPCP-guided care of a patient being provided warfarin management in an outpatient warfarin management clinic.
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KEY WORDS
• Pharmacists’ Patient Care Process • critical thinking • problem solving • anticoagulation • warfarin • international normalized ratio • drug interaction • diet • vitamin K
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Anticoagulation management serves an important role in preventing thromboembolic events that are related to stroke, heart attack, deep vein thrombosis/pulmonary embolism (DVT/PE), among others. According to the Centers for Disease Control (CDC), each year in the United States, as many as 795,000 people have a stroke and 900,000 people could be affected by DVT/PE. The vast number of patients who can benefit from anticoagulation medications warrants the participation of ambulatory pharmacy services to help manage the patient’s anticoagulation therapy.
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Among the different classes of anticoagulation medications are the vitamin K antagonist, warfarin, and the Novel Oral Anticoagulants (NOACs) that include direct thrombin inhibitors (dabigatran) and factor Xa inhibitors (apixaban, betrixaban, edoxaban, and rivaroxaban). NOACs have fewer drug–drug interactions than warfarin, and unlike warfarin, they do not require routine laboratory monitoring. These are among the reasons that NOACs are supplanting the use of warfarin for anticoagulation therapy.1 However, warfarin is favored under some circumstances, and currently there are 20 million Americans taking warfarin, with an additional 2 million who start taking the medication each year.2
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Warfarin requires frequent drug therapy monitoring due to a variety of reasons, including optimizing the dosing to assure proper efficacy for thromboembolism prevention and to reduce the risk of bleeding. The unique drug properties associated with warfarin, such as slow onset of action and long half-life, complicated pharmacokinetics, pharmacogenomic variance,3 drug–drug and drug–food interactions4 warrant the need for warfarin drug therapy management by the ambulatory care pharmacist.
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OUR PRACTICE—AN OUTPATIENT PHARMACIST MANAGED WARFARIN CLINIC
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Our practice is a pharmacist-managed outpatient clinic overseen by a hematologist. The patient population includes patients who have suffered from a thromboembolic event and were initiated warfarin during a recent hospital admission, patients referred by a primary care physician (PCP) for chronic anticoagulation management, and patients who are on a medical assistance program who are not currently under the care of a PCP. Currently in our clinic, the patient population ranges in age from the 20s to 90s, with most of the patients being over 50 years of age.
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The pharmacist’s responsibilities are to initiate and optimize warfarin therapy, monitor its therapeutic effects, assess drug–drug and drug–food interactions, and provide overall ...