Anticoagulated patient with an acute odontogenic infection requiring extraction
A 68-year-old man attends your clinic with a five-day history of increasing pain and swelling over the lower right first molar (46). He had a mechanical mitral valve replacement in 2019, with a target INR of 2.5–3.5, and takes warfarin 5 mg daily plus amlodipine 10 mg for hypertension. He is otherwise well, has no history of abnormal bleeding or liver disease, and has not seen a dentist for six years. He is apyrexial apart from a temperature of 37.9 °C, opens 35 mm, and has a fluctuant buccal swelling next to 46 with no dysphagia, no sublingual swelling and no trismus beyond the swelling. Tooth 46 is grossly carious, tender to percussion, grade II mobile with a 7 mm buccal pocket. His INR, taken this morning, is 3.4. The duty dentist proposes to stop warfarin for three days, extract 46 at a later visit, and start metronidazole 400 mg three times daily in the meantime.
1. Critique the duty dentist's plan. Is stopping warfarin correct, and is an INR of 3.4 unsafe for this patient?
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The plan is wrong on three counts.
- The indication decides the target range, not the number alone. Warfarin here is for a mechanical mitral valve, where the accepted therapeutic range is 2.5–3.5, not the 2.0–3.0 used for atrial fibrillation. An INR of 3.4 is therefore in range, not over-anticoagulated.
- Dental guidance (for example SDCEP) is that simple extractions should not be delayed, and warfarin should not be stopped, when the INR is within the therapeutic range and 4.0 or below. Local measures control bleeding. Interrupting anticoagulation without bridging exposes him to valve thrombosis and embolic stroke - a far greater risk than post-extraction oozing.
- Metronidazole is a poor choice here. It inhibits CYP2C9 and raises the INR, compounding bleeding risk, and it is being used as a substitute for source control.
- Delay is itself harmful. A fluctuant swelling with a low-grade temperature is a spreading odontogenic infection; antibiotics without drainage or extraction will not resolve it and may progress to a fascial space infection.
The correct approach is same-visit source control with local haemostasis, after confirming the INR result is current.
2. Describe how you would manage the infection and carry out the extraction, including local haemostatic measures and post-operative advice.
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Confirm the INR is within 24–72 hours of the procedure - today's result is acceptable if the extraction is done now. Check that no new interacting medicine has been started.
Source control: drain the buccal swelling and extract 46 under local anaesthesia with a vasoconstrictor (2% lidocaine with 1:100,000 adrenaline), using an aspirating technique and a slow injection. An inferior alveolar nerve block is acceptable when the INR is in range, but a buccal infiltration with an intraligamentary supplement avoids a deep block.
Haemostasis:
- Atraumatic extraction, gentle curettage, removal of granulation tissue.
- Oxidised cellulose or gelatin sponge placed in the socket.
- Resorbable 3-0 or 4-0 figure-of-eight suture.
- Pressure pack with moist gauze for 20 minutes, inspected before discharge.
- Tranexamic acid 4.8% mouthwash, 10 mL four times daily for 2 days.
Advice: no rinsing, spitting, smoking, alcohol, hot drinks or exercise for 24 hours; soft diet; sleep with the head raised; return immediately if bleeding is not controlled by 20 minutes of firm pressure.
Analgesia: paracetamol 1 g four times daily (maximum 4 g) with or without codeine. Avoid NSAIDs - they add an antiplatelet effect and gastrointestinal bleeding risk on warfarin.
Endocarditis prophylaxis: a mechanical prosthetic valve is a high-risk cardiac condition. Where local policy follows AHA or ESC guidance, give amoxicillin 2 g orally 30–60 minutes pre-operatively; NICE advises against prophylaxis, so follow your local guideline and document the decision.
3. Justify your antibiotic choice in this patient and flag any interaction risks.
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First-line is amoxicillin 500 mg three times daily for 3–5 days. It covers the streptococci and oral anaerobes usually responsible and has a low interaction profile. It is an adjunct to drainage and extraction, not an alternative to them - prescribe because there is spreading infection with swelling and a raised temperature, and review at 48–72 hours.
Why not metronidazole routinely, alone or in combination: metronidazole inhibits CYP2C9 and reduces warfarin metabolism, raising the INR within 3–5 days; combined use has caused clinically significant bleeding. If anaerobic cover is essential (severe cellulitis spreading beyond the buccinator, or a deep space infection), make the decision with the anticoagulation service: check the INR at 3–5 days, warn the patient about bleeding and bruising, and consider a small warfarin dose reduction rather than stopping it.
Also avoid co-trimoxazole, erythromycin or clarithromycin, fluconazole and high-dose aspirin for the same interaction reasons.
Document the indication, duration and review plan. If the swelling is not settling by 48 hours, or he develops dysphagia, floor-of-mouth raising or systemic signs, refer for admission and intravenous therapy.