The impact of pharmacist-managed oral anticoagulation therapy in older veterans

Abstract

Background: Older adults frequently have conditions requiring oral anticoagulation. Although clearly benefiting from oral anticoagulation, they are at increased risk for bleeding complications. Regular monitoring to optimize anticoagulation and to reduce the chance of major bleeding complications is required. The impact of oral anticoagulation monitoring by pharmacists in patients older than 75 years of age has not been described well.

Objective: To compare warfarin therapy prescribed and monitored by physicians to a pharmacist-monitored anticoagulation service in a cohort of older veterans.

Methods: Retrospective chart review utilizing the Houston VA Medical Center's pharmacy database. Among all outpatients aged 75 years or older filling warfarin prescriptions between 1 March 2003 to 1 March 2005, and who were either monitored in a pharmacist's clinic or not, 103 patients per group were randomly selected. Information on demographics, indication for and length of warfarin therapy, INR values, and thromboembolic and bleeding events were abstracted. Differences were analysed using chi-squared test, Fisher's Exact test, and unpaired Student t-test.

Results: A total of 1521 patients (440 in the pharmacist-monitored group, 1081 in the traditionally monitored group) met our inclusion criteria. One hundred and three patients per group were randomly selected for chart review. Although no significant difference in percentage of therapeutic INR values (48.1% pharmacist group, 46.4% conventional group) or in the incidence of major bleeding events was found, thromboembolic events occurred significantly less frequently in the pharmacist-monitored group (2 events vs. 12 events, P = 0.01). Minor bleeding events were more frequent in the pharmacist-monitored group (50 vs. 17, P < 0.01). However, time to follow-up after a sub- or supra-therapeutic INR was significantly shorter in the pharmacist monitored group (22 days vs. 68 days, and 14 days vs. 32 days, respectively).

Conclusion: Pharmacist-monitored anticoagulation was associated with reduced thromboembolic events, an increase in minor bleeding events, and no difference in major bleeding events. Overall such monitoring by pharmacists should be recommended for older adults.