Key result
Antibiotic coadministration and acute upper respiratory tract infection increased the risk of a follow-up INR ≥5.0 compared to stable controls (3.2% and 2.6% vs 1.2%, respectively).
Why the study?
Does antibiotic coadministration or acute upper respiratory tract infection increase the risk of excessive anticoagulation in patients on stable warfarin therapy?
Population
12,006 patients on stable warfarin therapy (mean age 68.3 years, 44.4% with atrial fibrillation as indication)
Comparison
Coadministration of antibiotics or medical visit… vs Patients purchasing a warfarin refill without…
Design
Cohort
Authors
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May support closer INR monitoring during antibiotics or URI in warfarin patients; leaves open independent causality versus illness effects.
Cohort (n=12,006)
Does antibiotic coadministration or acute upper respiratory tract infection increase the risk of excessive anticoagulation in patients on stable warfarin therapy?
Absolute Event Rate: 3.2% vs 1.2%
p-value: p=<0.001
Both acute upper respiratory tract infections and antibiotic use independently increase the risk of excessive anticoagulation in patients on stable warfarin, though the absolute risk of clinically relevant INR increases remains low.
Clark et al. (2014) conducted a cohort in Stable warfarin therapy (n=12,006). Antibiotic coadministration vs. Stable controls (warfarin refill) and sick controls (upper respiratory tract infection without antibiotics) was evaluated on Proportion of patients experiencing a follow-up INR of 5.0 or more (p=<0.001). Antibiotic coadministration and acute upper respiratory tract infection increased the risk of a follow-up INR ≥5.0 compared to stable controls (3.2% and 2.6% vs 1.2%, respectively).
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