Does prophylactic antibiotic administration for tooth extraction affect PT-INR in patients taking warfarin?

Background: Various antibiotics and analgesics have been reported to interact with　warfarin. Reports that investigate the effects of medication taken for just a few days during tooth extraction on the prothrombin time-international normalized ratio (PT-INR) are rare. Methods: : A total of 110 patients receiving long-term stable warfarin therapy underwent tooth extraction without interruption of warfarin treatment. INR values were measured one month before the tooth extraction, the day of the extraction, and one week after the extraction. We investigated the changes in INR values between the day of extraction and one week after extraction, as well as the various risk factors for increases in INR values. Results: : Before and after tooth extraction, the number of patients taking cefcapene pivoxil, amoxicillin, and azithromycin was 57, 36, and 8, respectively. Nine patients were administered ampicillin before tooth extraction and received amoxicillin after their tooth extraction. One week after tooth extraction, the INR values increased beyond the therapeutic range in 3 out of 110 patients (2.7%). The INR values before tooth extraction in these three patients were close to 3.0. The INR value increased by more than twice as much in 1 out of 110 patients (0.9%). Conclusion: Our results suggest that prophylactic antibiotic administration has little effect on INR values when patients on stable warfarin therapy undergo tooth extraction. Surgeons have to take attention if the patients whose INR values are close to 3.0 before their extraction.