• If patients on warfarin who require dental surgery have an International Normalised Ratio (INR) of below 4.0, they can usually receive their dental treatment in primary care without needing to stop their warfarin or adjust their dose.
• The risk of thromboembolism after temporary withdrawal of warfarin therapy outweighs the risk of oral bleeding following dental surgery.
• Patients on warfarin may bleed more than normal, but bleeding is usually controlled with local measures.
Advice to be given to patients
Advice for patients is available in the patient leaflet, Oral Anticoagulant Therapy: Important information for dental patients.
There have been anecdotal reports that amoxicillin interacts with warfarin causing increased prothrombin time and/or bleeding, but documented cases are relatively rare. Patients requiring a course of amoxicillin should be advised to be vigilant for any signs of increased bleeding.
Clindamycin is restricted to specialist use and should not be used routinely for dental infections due to its serious side effects. There is a single case report of an interaction between warfarin and clindamycin.
Erythromycin and other macrolide antibiotics (for example, azithromycin)
Macrolide antibiotics interact with warfarin unpredictably and only in certain individuals. Patients should be advised to be vigilant for any signs of increased bleeding.
If increased bleeding occurs then the patient should be advised to contact the GP or anticoagulant clinic to arrange additional INR testing and dose review.
Metronidazole interacts with warfarin and should be avoided if possible. If it cannot be avoided, the warfarin dose may need to be reduced by a third to a half, and re-adjusted again when the antibiotic is discontinued. Contact the GP or anticoagulant clinic to arrange additional INR testing and dose review.
Non-steroidal anti-inflammatory drugs
Drugs including ibuprofen, aspirin and diclofenac should not be used as analgesics in patients taking warfarin.
Dental surgery covered by this advice includes:
Treatment where the INR does not need to be checked:
Treatment where the INR does need to be checked (follow flow diagram):
• Minor oral surgery
• Periodontal surgery