Age and dosing have a significant inverse relationship

By: Alere Staff
Publication Date: Tue, 11/08/2011

A study published in June 2005 CHEST publication evaluated 12, 202 patients (4,616 prospective, 7,586 retrospective) to determine age and gender on maintenance doses of warfarin. Accurate dosing is critical to patient safety, particularly in elderly patients. The authors noted that since testing is not practical for daily evaluation, accurate maintenance dosing can reduce over-anticoagulation and associated bleeding.1

More frequent dosing was inversely related to patient age. Gender played a strong role. Age and gender was evident in that the average more frequent dose for men under 50-years old was 48mg vs. only 22mg/week for women 80-years or older.1

The variances of dosing requirements for an aging population challenge the traditional practice of initiating 5mg/day. The authors state the majority of elderly patients will face over-anticoagulation if initiated at 5mg per day.

Home monitoring becomes a practical tool for elderly where small changes in dosing results in large clinical consequences. The elderly make up a special high-risk group due to the many medications (polypharmacy), risk of falling and increased risk of peripheral bleeding.

Patients in their 80’s have shown relative ease of performing their own home test. For those deemed incapable of performing their own test due to visual limitations or cognitive limitations, a family member or neighbor can easily perform the finger stick.

Ability is not a criteria for selecting a patient for more frequent home testing. Patients at risk for bleeding or stroke and improving control of the International Normalized Ratio (INR) are the most appropriate patients.

  1. Garcia D et al. Warfarin maintenance dosing patterns in clinical practice: Implications for safer anticoagulation in the elderly population. Chest. 2005. Jun; 127:2049-56.