Clinical impact of temporary therapy interruptions on anticoagulation control in patients treated with warfarin.

Clinical impact of temporary therapy interruptions on anticoagulation control in patients treated with warfarin.

Boros Melanie L; Rybarczyk Amy M; Gallegos Patrick J; Zimmerman Jacob P

American Journal of Therapeutics

2013

2013-05

This retrospective cohort study was completed to describe the impact of short-term therapy interruptions on anticoagulation control in patients receiving warfarin. Patients seen in a pharmacist-managed anticoagulation clinic were included if they were on a stable warfarin dose and then underwent a planned interruption in therapy. Patients were excluded if phytonadione was administered before the interruption or if medications known to interact with warfarin were altered during the interruption. Data were analyzed for 2 groups: (1) patients with a single interruption in therapy (group 1) and (2) patients with a single interruption in therapy plus patients with an extended interruption in therapy (group 2). The primary endpoint was the change in weekly maintenance warfarin dose from preinterruption to postinterruption. Evaluation of 199 patients resulted in 31 interruptions in group 1 and 34 interruptions in group 2. A change in dose was required in 58% of patients in group 1 and 56% of patients in group 2. The mean absolute change in dose was 2.03 ± 2.79 mg (P \textless 0.003) in group 1 and 1.96 ± 2.72 mg (P \textless 0.002) in group 2. For the majority of patients, the dose change represented \textless10% of their preinterruption weekly dose. Of patients requiring a dose change, 50% required an increase in dose. In conclusion, close follow-up is warranted after a warfarin therapy interruption as dose adjustments will likely be needed to regain anticoagulation control and the direction of this dose change cannot be predicted.

Female; Male; Aged; Prospective Studies; International Normalized Ratio; Drug Administration Schedule; Preoperative Care; Postoperative Care; Human; Middle Age; Retrospective Design; Dose-Response Relationship; Drug; Treatment Outcomes; Drug Monitoring; Anticoagulants – Therapeutic Use; Anticoagulants – Administration and Dosage; Atrial Fibrillation – Drug Therapy; Blood Coagulation Disorders – Drug Therapy; Coronary Thrombosis – Drug Therapy; Euthanasia; Passive; Venous Thromboembolism – Drug Therapy; Warfarin – Administration and Dosage; Warfarin – Therapeutic Use

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