Clinical, drugs interactions and pharmacogenetics evaluation of Warfarin treatment in an elderly patient: a case report

G. Corbi 1 , V. Simeon 2 , V. Conti 2 , N. Ferrara 3 , F. Cacciatore 4 , A. Filippelli 2

1 Department of Medicine and Health Sciences, University of Molise, Campobasso, Italy; 2  Department of Medicine and Surgery, University of Salerno, Baronissi (SA), Italy; 3  Department of Anesthesiology, Surgical and Emergency Sciences, Second University of Naples, Italy; 4  “S. Maugeri” Foundation, Scientific Institute of Telese Terme, IRCCS, Telese Terme, Italy

Introduction. Cardiovascular diseases are very prevalent in the elderly population and characterized by high complexity, poor prognosis and comorbidity. Atrial fibrillation is common in elderly patients both in institutionalized in long-term care facilities and in community associated or not to congestive heart failure, but the management with anticoagulant oral therapy is highly variable and problematic.

Case presentation. Here we describe a case report on a patient treated with amiodarone and heparine for acute atrial fibrillation episodes. Three years before he underwent partial intestinal resection for bowel cancer. During Warfarin therapy a treatment with neomycin sulphate/bacitracin was started. After three days of Warfarin therapy an International Normalised Ratio (INR) value > 10 was found. No bleeding occurred, but the period of hospitalization was prolonged. After genotype assessment for CYP2C9 and VKORC1 he was found to be an intermediate metabolizer with the genotype of CYP2C9*1/*2, and homozygous for VKORC1*2/*2. By using the International Warfarin Pharmacogenetics Consortium algorithm, the estimated therapeutic Warfarin dose was 1.8 mg/day, less than a half of prescribed dose.

Conclusion. A preventive pharmacogenetic assessment could be very useful in defining the right dose of Warfarin to be administered especially in elderly patients institutionalized in long-term care facilities with comorbidity and polypharmacy.

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