Clinical Factors Associated with Low, Medium and High Warfarin Dose Requirements in Adult and Older adult Patients at Loei Hospital
Keywords:
clinical factor, warfarin dose, older adult, adultAbstract
Background and Objective: Warfarin dose requirements were different among patients. Especially, older adult patients have greater risk of overdose and bleeding than younger patients. Therefore, this study aimed to determine the clinical factors associated with low, medium and high warfarin dose requirements in adult patients aged 20-59 years and older adult patients aged ≥ 60 years.
Methods: An 8 year retrospective descriptive study was conducted from January 2014 to December 2021 in adult and older adult patients who received warfarin and had an INR between 2.0-3.0. Clinical data, e.g., age, gender, body weight, stage of chronic kidney disease, comorbidity and concomitant medications were documented.
Results: A total of 672 patients, 63.7% older adults, 52.7% females. The mean age of all patients, adult patients and older adult patients were 63.4±11.7, 51.2±6.8 and 70.3±7.3 years, respectively. The mean warfarin dose were 20.4 ± 9.6, 25.3±9.9, 17.6±8.3 mg/week, respectively. The mean dose of warfarin in the older adult was about 30% lower than adult patients. In adult patients, warfarin doses were significantly higher in males than in females (p=0.004). Overweight patients required higher doses in both groups. Chronic kidney disease stage 3-5 (<60 mL/min/1.73m2) resulted in a significant dose reduction in the older adult patients (p<0.001). The mean low, medium, and high dose in the adult group were 14.1±2.5, 24.6±4.4, and 42.7±7.3 mg/week, respectively, while in the older adult were 8.7±1.5, 15.2±2.4 and 27.5±7.0 mg/week, respectively. Adult patients younger than 50 years and overweight tended to require higher doses, while older adult patients aged 70 years and older, underweight, chronic kidney disease stage 3-5, anemia, history of bleeding disorders, liver disease and taking amiodarone tended to require lower doses. Age, body weight, and chronic kidney disease stage 3-5 were the most influential factors for predicting warfarin doses.
Conclusions: Warfarin should be initiated or adjusted at a lower dose in older adult patients than in adult patients. Clinical factors were considered, including age, body weight, stage of Chronic kidney disease, anemia, history of bleeding disorders, liver disease, and amiodarone intake.
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