The Impact of Pharmacist-Managed Service on Warfarin Therapy in Patients after Mechanical Valve Replacement

OBJECTIVE: To evaluate the impact of pharmacist interventions on international normalized ratio (INR) control during the warfarin initiation phase after mechanical valve replacement. METHODS: This was a retrospective cohort study conducted in a cardiovascular surgery ward in a tertiary hospital from August 1, 2015, to July 31, 2019. Patients aged ≥20 years who were admitted for mechanical valve replacement were enrolled in this study and further classified into conventional and pharmacist-managed warfarin therapy (PMWT) groups. All participants were prospectively followed up until the first outpatient appointment after valve replacement. The effectiveness outcomes were time in therapeutic range (TTR), time to therapeutic INR, number of patients with therapeutic INR at discharge and at first outpatient appointment, and length of hospital stay. The safety outcome was the number of patients with any supratherapeutic INR during the hospital stay. Multivariate logistic regression analyses were also used to determine the predictors of a therapeutic INR at discharge or with any supratherapeutic INR during admission. RESULTS: A total of 39 and 33 patients were enrolled in the conventional and PMWT groups, respectively. At discharge, 18 patients (46.2%) in the conventional group and 24 patients (72.7%) in the PMWT group had achieved the therapeutic INR (P=0.023). Compared to the conventional group, fewer patients in the PMWT group had supratherapeutic INR during hospital stay (35.9% vs. 9.0%, P=0.008). No significant differences were found in TTR, time to therapeutic INR, number of patients with therapeutic INR at return appointment, and length of stay between the study groups. In the multivariate regression analyses, PMWT predicted achieving therapeutic INR at discharge (odds ratio (OR) and 95% confidence interval (CI), 3.14 [1.08–9.14]) and was inversely associated with supratherapeutic INRs during admission (OR = 0.21 [0.05–0.82]). CONCLUSIONS: Among patients admitted for mechanical valve replacement, the implementation of PMWT was associated with optimal therapeutic INR at discharge and no supratherapeutic INR during admission. Therefore, pharmacist participation is essential for improving the quality of warfarin therapy.