Amoxicillin/clavulanic acid-warfarin drug interaction: a randomized controlled trial

AIMS

To investigate whether an interaction exists between amoxicillin/clavulanic acid (amoxiclav) and warfarin in patients treated with stable oral anticoagulant therapy.

METHODS

In a double-blind, cross-over, placebo-controlled study, 12 patients on stable warfarin therapy, received a 7 day amoxiclav regimen or placebo.

RESULTS

The mean maximum increase in INR observed was 0.22 ± 0.3 with amoxiclav vs. 0.24 ± 0.6 with placebo (P= 0.94). The day 7–day 1 factor II, R(–) and S(–) warfarin plasma concentrations were similar during the amoxiclav and placebo study periods (P= 0.81, P= 0.45, P= 0.75, respectively).

CONCLUSION

Amoxiclav did not modify anticoagulation in patients treated with stable warfarin therapy and without infection.