Warfarin and Heparin
Warfarin inhibits synthesis of Vitamin K dependent coagulation factors – II, VII, IX and X. It has a long half life of 20-60 hours and takes between 2-5 days for the effect to stop.
General Guidelines:
• Patients who have an International Normalised Ratio (INR) of 4.0 or below 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 outweighs the risk of bleeding following dental surgery
• Patients on warfarin bleed more than normal but bleeding is usually controlled with local measures.
Practicalities
• An INR needs to be taken no more than 72 hours prior to the procedure although many authorities feel this should be no longer than 48 hours. If the INR is >4.0 delay the procedure and refer to the anticoagulation service.
• Treatment should be undertaken in the morning and at the beginning of the week to allow management of any problems in the working day and working week.
• Use LA with a vasoconstrictor and avoid ID blocks if possible due to the risk of haematoma formation, however this is more of a theoretical risk.
• For extractions, gently pack the socket with a resorbable haemostatic agent and suture the socket.
• There is no indication for routine prescribing of antibiotics in this group of patients.
Drug Interactions
Always check the most up-to-date BNF prior to prescribing medications. Appendix 1 – Coumarins.
Amoxicillin – anecdotal reports of increased bleeding but documented cases are relatively rare. Pt’s should be vigilant for signs of increased bleeding
Clindamycin – single case report of an interaction between clindamycin and warfarin.
Erythromycin (and other macrolides) – interact with warfarin unpredictably.
Metronidazole – interacts with warfarin and should be avoided as much as possible
NSAIDs – drugs such as ibuprofen, aspirin and diclofenac should not be used as analgesics in patients taking warfarin
Miconazole – potentially serious interaction. Use nystatin if possible
Carbamazepine – decreases action of warfarin
Management of Warfarinised Surgical Patients
For more major surgery then stop Warfarin and commence a full Heparinisation Regime. Re-institute Warfarin post-operatively. Consider the use of transexamic acid mouthwashes. Transexamic acid is only available in tablets but can be dissolved to make a mouthwash however some pharmacies can make up mouthwash preparations if sufficient notice is given.