Optimization of Inpatient Warfarin Therapy: Impact of Daily Consultation by a Pharmacist-Managed Anticoagulation Service

Abstract

OBJECTIVE: To determine the effect of daily consultation by a team of hospital pharmacists on the accuracy and rapidity of optimizing warfarin therapy. DESIGN: Comparison of a historical control cohort with a prospective cohort matched for treatment indication. SETTING: A 400-bed university teaching hospital. PATIENTS: Sixty consecutive patients hospitalized in 1992 and starting warfarin for the first time, with anticoagulation therapy managed by physicians, were compared with 60 patients matched for warfarin indication hospitalized in 1995, but with anticoagulation therapy managed with pharmacy consultation. RESULTS: Pharmacist management of initial warfarin therapy resulted in a significant reduction in the length of hospitalization compared with physician dosing, from 9.5 ± 5.6 days to 6.8 ± 4.4 days (p = 0.009). The number of patients and patient-days with international normalized ratio (INR) values >3.5 were reduced by pharmacist dosing from 37 patients and 142 days to 16 patients and 29 days, respectively (p < 0.001). Similarly, the number of patients and patient-days with INR >6.0 were reduced from 20 patients and 50 days to two patients and six days, respectively (p < 0.001). There were six documented bleeding complications in 1992 compared with one in 1995 (p = 0.11). The mean INR at discharge was significantly lower in the pharmacy surveillance group, 2.6 ± 0.58, compared with the physician cohort, 3.3 ± 2.1 (p = 0.07). Readmissions after discharge due to bleeding or recurrent thrombosis were reduced from five (at 1 mo) and 10 (at 3 mo) to two and five readmissions, respectively, by pharmacist intervention (p = 0.43). The number of patients with concurrently prescribed drugs known to significantly interact with warfarin was significantly lower (6 vs. 13; p = 0.02) in the pharmacy surveillance group. CONCLUSIONS: Among patients starting warfarin for the first time, daily consultation by a pharmacist significantly decreased the length of hospital stay and the number of patients who received excessive anticoagulation therapy. These findings translate into improved quality of care and potentially significant cost savings.