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

Author(s): Zhang Q, Simoneau G, Verstuyft C, Drouet L, Bal dit Sollier C, Alvarez JC, Rizzo-Padoin N, Bergmann JF, Becquemont L, Mouly S

Affiliation(s): University of Paris VII-Denis Diderot, Therapeutic Research Unit, Department of Internal Medicine, Lariboisiere Hospital, Paris, France.

Publication date & source: 2011-02, Br J Clin Pharmacol., 71(2):232-6.

Publication type: Randomized Controlled Trial; Research Support, Non-U.S. Gov't

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. (c) 2011 The Authors. British Journal of Clinical Pharmacology (c) 2011 The British Pharmacological Society.