Assessment of an age-adjusted warfarin initiation protocol

Area of Science:

• Pharmacology
• Clinical Pharmacy
• Internal Medicine

Background:

• Warfarin is a widely prescribed anticoagulant, but achieving and maintaining a stable therapeutic International Normalized Ratio (INR) can be challenging.
• Initiation protocols significantly impact warfarin's efficacy and safety, influencing time to therapeutic anticoagulation and risk of bleeding or clotting.
• Optimizing warfarin dosing is crucial for patient outcomes in anticoagulation therapy.

Purpose of the Study:

• To evaluate the efficacy of an age-adjusted warfarin initiation protocol in achieving a stable International Normalized Ratio (INR).
• To determine the incidence of overanticoagulation (INR ≥4) within the first week of therapy using this protocol.
• To assess the protocol's ability to manage variables affecting warfarin dosing.

Main Methods:

• A prospective study involving inpatients and outpatients initiating warfarin therapy at two teaching hospitals.
• Patients were dosed using an age-adjusted protocol over a 4-day titration period.
• Data collected included time to achieve a stable INR (2-3) and instances of INR ≥4.

Main Results:

• After a 4-day protocol, 63% of patients achieved a stable INR; this increased to 86% after an additional 2 days of physician-guided adjustments.
• Only 7% of patients (5/73) experienced an INR ≥4, indicating low overanticoagulation rates.
• The protocol effectively managed influencing factors such as weight, gender, and other risk factors, with INR-driven adjustments on days 3 and 4.

Conclusions:

• The age-adjusted warfarin initiation protocol facilitates rapid achievement of a stable INR with a low risk of overanticoagulation.
• Patients with low serum albumin levels (<3.0 g/dL) may exhibit increased sensitivity to warfarin during the initial loading phase.
• This protocol shows promise for safe and efficient warfarin initiation, though careful monitoring for specific patient groups is advised.