it is common that antibiotic eg amoxycillin taken while on warfarin dosage increases INR level, but my INR level in this situation has decreased to 1.4 (range 2-3); I have completed my week long dosage of the antibiotic and felt OK with no adverse symptons all along. My GP directed me to continue the same warfarin dosage and have INR check in a week for further directions
Hi, Thank you for your query. I can understand your concerns. Amoxicillin oral increases effects of warfarin oral.  INR levels may increase. Use with caution ;Although the mechanism for this interaction is not fully known, it is suspected that a decrease in vitamin K-producing gut flora with resulting vitamin K deficiency would be the most likely contributing factor. Using warfarin together with amoxicillin may increase the risk of bleeding, especially if you are elderly or have kidney or liver impairment. You may need more frequent monitoring of your prothrombin time or INR by your doctor to safely use both medications.However, some study did not find Amoxiclav(amoxicillin/clavulanic acid) modifying anticoagulation in patients treated with stable warfarin therapy and without infection. This may explain your INR not going up with concurrent amoxicillin therapy. Regards 