Warfarin in Dentistry: Extractions, INR, Antibiotics, NSAIDs, and Bleeding Control

Warfarin is a vitamin K antagonist, and the dental question is rarely whether to stop it. For most outpatient procedures the evidence says continue, control bleeding locally, and manage the two things that actually move risk: the INR on the day, and what you prescribe afterwards. This page is the overview. The narrow question of which INR is safe for an extraction has its own evidence summary, and the hold-or-continue thresholds for warfarin, the DOACs, Prolia, and GLP-1 agonists sit side by side in the medication hold-times brief.

Extractions: continue, check the INR, control bleeding locally#

The Spanish Society of Oral Surgery's 2024 guideline recommends continuing a coumarin anticoagulant through extractions, with local hemostatic measures and without pharmacological reversal. The thresholds behind that recommendation: continuation is documented safe for simple extractions when the INR is below 3.5, and up to 4.0 for uncomplicated cases according to some experts; one to three teeth have been extracted safely below 3.5 in the absence of other bleeding risks; four or more teeth carry higher postoperative bleeding risk. The guideline draws its own line lower, advising physician contact once the INR exceeds 3 or several teeth are involved. In a stable patient the INR should be checked within 72 hours of the procedure. The source for each of those figures is laid out claim by claim in the warfarin answer.

Almost half of anticoagulated patients have difficulty keeping the INR in range, according to the patient-association data the guideline cites. A patient whose recent readings swing is a physician call, whatever today's number says.

What counts as low and high bleeding risk#

Procedure, not drug, sets the risk band. One to three extractions is low risk. Six or more extractions, surgery that raises a flap, or placing several implants is high risk, and that is where the physician conversation and any dose modification belong. The practice notes in the brief apply the same rule across every antithrombotic.

Antibiotics that move the INR#

A 2023 review of warfarin and antibiotic interactions found significant INR increases with penicillin derivatives, fluoroquinolones, trimethoprim-sulfamethoxazole, and macrolides, and a positive association with a raised INR even for cephalosporins and amoxicillin/clavulanate, which do not act through cytochrome P450. The dental specifics:

• Metronidazole potentiates warfarin. In one study it pushed the INR above 6 in 4.9% of patients; in another, 23.3% of patients went supratherapeutic, meaning an INR above 3. Avoid it in a warfarin patient unless the prescriber is arranging an INR check.
• Macrolides. Azithromycin carried a twofold increase in serious bleeding compared with low-risk antibiotics, and in paediatric cardiac patients the mean INR rose from 2.7 to 3.6 on a macrolide.
• Amoxicillin has the weakest signal. Some sources report no interaction, and in a gastrointestinal-bleeding study amoxicillin and ampicillin showed no significant interaction where trimethoprim-sulfamethoxazole did. But case reports describe INR elevation and bleeding from 7 days after starting to 9 days after stopping amoxicillin or amoxicillin/clavulanate, and higher clavulanate doses carried more over-anticoagulation risk.

The practical rule: when a warfarin patient needs a course longer than a few days, tell the anticoagulation clinic or prescriber which drug and for how long, so the INR can be checked mid-course. The review's own recommendation for cytochrome P450 inhibitors is a warfarin dose reduction, which is the physician's decision, not the dentist's.

Analgesics: acetaminophen first, NSAIDs with caution#

Acetaminophen is the default, but it is not inert at sustained doses. A randomised trial of 45 stably anticoagulated patients found that 2 g or 3 g a day for 10 days raised the INR by about 0.7 against placebo, with the rise significant from day 3. A short post-extraction course is unlikely to matter; a week or more at those doses warrants an INR check.

NSAIDs add bleeding risk on top of any anticoagulant. In a nationwide cohort of 114,119 patients with atrial fibrillation, NSAID use alongside oral anticoagulation raised hospital-diagnosed bleeding from 3.9 to 6.2 events per 100 person-years, an adjusted hazard ratio of 1.81 overall and 1.46 for warfarin specifically, with a number needed to harm of 43 patients treated for a year. Gastrointestinal bleeding more than doubled, and the risk was not confined to the gut. That is a population figure for ongoing use rather than a two-day course, but it is the reason to reach for acetaminophen first and to keep any NSAID course short and known to the prescriber.

Bleeding control chairside#

The Spanish guideline found no single local measure superior and recommends the ones with the most evidence: sutures, collagen or cellulose sponges, and compression with gauze soaked in tranexamic acid, as a Grade C recommendation. Its Grade D recommendations add continuing the anticoagulant rather than substituting a pharmacological measure, and, for drugs where it applies, operating at the trough of plasma concentration. Send the patient home with written instructions on pressure, what a normal ooze looks like, and when to phone.

When to call the physician#

• INR above 3 on the pre-operative check, or no recent reading.
• Four or more extractions, flap surgery, or multiple implants.
• An interacting antibiotic course is planned, especially metronidazole or a macrolide.
• Unstable INR history, a mechanical heart valve, or a recent thromboembolic event.
• Any plan to modify the warfarin dose, which stays with the prescriber.

The extraction thresholds, DOAC hold times, and antiresorptive timing that sit alongside this are compared in the medication hold-times brief.