Oral anticoagulants in the elderly

Area of Science:

• Gerontology
• Pharmacology
• Clinical Pathology

Background:

• Warfarin therapy requires regular monitoring of prothrombin time, expressed as International Normalized Ratio (INR).
• Achieving and maintaining a target INR range is crucial for therapeutic efficacy and minimizing bleeding or thrombotic risks.
• Age-related physiological changes may influence warfarin metabolism and response, potentially affecting INR stability.

Purpose of the Study:

• To investigate the relationship between patient age and the occurrence of elevated International Normalized Ratio (INR) values.
• To identify age as a potential risk factor for unstable prothrombin time results during warfarin therapy.

Main Methods:

• Retrospective analysis of 34,998 prothrombin time tests from 2,379 patients aged 40-89 years over one year.
• Data collection included INR values, warfarin dosage, and patient demographics.
• Statistical analysis was performed to assess the risk of INR values ≥5 in relation to age.

Main Results:

• Over 21% of patients experienced at least one INR value of 5 or higher.
• Elderly patients exhibited higher maximum and lower minimum INR values compared to younger cohorts.
• The risk of INR values ≥5 increased by 15% for every 10-year increase in age, even after adjusting for warfarin dose and test frequency.

Conclusions:

• Age is a significant independent risk factor for achieving excessively high INR values during warfarin therapy.
• Older patients are more prone to experiencing unstable prothrombin time results.
• These findings suggest a need for age-specific monitoring strategies in warfarin management.