NSAIDs and warfarin (or acenocoumarol)

The short answer: Avoid NSAIDs. Use paracetamol (acetaminophen) or metamizole. If essential, watch the INR and add a PPI. (Metamizole is not sold in the UK or the US — paracetamol is the substitute there.)

Why this matters

Both an NSAID and a vitamin K antagonist increase bleeding risk on their own — an NSAID by reducing platelet function and irritating the stomach lining, warfarin and acenocoumarol by design. Stack them and the risk is not additive, it compounds: a peptic bleed that would have stayed silent on warfarin alone can become a GI bleed.

In short: Additive antiplatelet effect + gastric injury.

What to do at the counter

The safer painkiller is paracetamol (acetaminophen), up to 3-4 g a day, for as short a course as the pain needs.
If an NSAID is genuinely unavoidable — a short course, prescribed, no alternative — the INR needs checking, and a PPI (like omeprazole) covers the stomach.
This applies to aspirin too, not just ibuprofen: low-dose aspirin on top of warfarin is a deliberate prescribing decision, never an OTC add-on.

Which medicines this covers

NSAIDs

ibuprofen, naproxen, diclofenac, dexketoprofen, ketoprofen, celecoxib, etoricoxib, indomethacin, piroxicam, meloxicam, aceclofenac

Anticoagulants

acenocoumarol, warfarin

Checking a longer medication list, or a pair not listed here? Run it through the full drug interactions checker — it covers the whole list at once, pair by pair.

For guidance only. This does not replace the pharmacist's professional judgement or medical advice. Check the official Summary of Product Characteristics before any clinical decision. See the clinical content policy.

Frequently asked questions

Is paracetamol completely safe with warfarin?

It is the analgesic of choice, and for occasional use there is nothing to watch. At doses above 2 g a day for more than about a week, INR can drift up slightly — worth a mention if someone is taking regular high-dose paracetamol long-term, not a reason to avoid it for a headache.

What about topical NSAID gels — ibuprofen gel, diclofenac gel?

Systemic absorption through the skin is low, and the interaction risk with warfarin is correspondingly small. It is still worth a mention if someone is using a lot of it over a large area, but it is not the same conversation as an oral NSAID.

Does this apply to the newer anticoagulants (DOACs) too?

The mechanism and the size of the risk are similar, but the practical advice differs slightly — see the separate guide on NSAIDs and blood thinners (DOACs).