Frequency and clinical outcomes of pharmacist-driven switching from warfarin to direct oral anticoagulants in an underserved patient population: A retrospective cohort study

Abstract

Purpose: Direct oral anticoagulant (DOAC) medications have improved safety, efficacy, and laboratory monitoring requirements compared to warfarin. However, available data are limited on the frequency and clinical outcomes of pharmacist-driven warfarin-to-DOAC switches. We aimed to quantify the frequencies and rationale of warfarin-to-DOAC switches in an underserved population. We also assessed clinical outcomes and compliance with recommended laboratory monitoring after switches.

Methods: This retrospective cohort study included adult (age 18 years or older) patients on warfarin who were assessed by a clinical pharmacist for switch appropriateness to a DOAC. Study data were collected via manual chart review and included demographics, comorbid illnesses, switch status, the rationale for or against switching, incidence of thromboses and bleeds within 6 months of the switch assessment, and the time to the first complete blood count and renal and hepatic function tests after the switch. Statistical analysis utilized descriptive statistics, including the mean and SD, median and interquartile range, and frequencies and percentages.

Results: Among 189 eligible patients, 108 (57%) were switched from warfarin to a DOAC. The primary rationales for switching were less monitoring (64%) and labile international normalized ratio (32%). The main reason against switching was DOAC inappropriateness (53%), such as in morbid obesity (14%). Patient preference was commonly cited in both groups (54% and 36%, respectively). The overall incidence of thrombotic events (9%) and bleeds (15%) after switch assessment was low. Laboratory monitoring after switches was consistent with current recommendations.

Conclusion: No increase in harm was observed 6 months after switch assessment when pharmacists at a family medicine clinic switched underserved patients from warfarin to DOACs.

Keywords: anticoagulation; direct oral anticoagulants; federally qualified health center; pharmacist switch assessment; warfarin.