When two or more medicines are taken at the same time, the effects of one of the medicines can be altered by the other. This is known as a drug-drug interaction. Warfarin can interact with many medicines.
If you want to check that your medicines are safe to take with warfarin, ask your doctor or local pharmacist, or read the patient information leaflet that comes with your medicine.
Lots of herbal medicines and supplements can interact with warfarin. Do not start taking any new herbal medicine or supplement without checking with your anticoagulant clinic, GP or pharmacist.
Aspirin and other painkillers
If you are on warfarin:
- do not take aspirin or drugs that contain aspirin because bleeding may happen
- do not take ibuprofen
- you can take paracetamol but do not take more than the recommended dose
Interactions with food
Some foods, such as spinach and broccoli, contain vitamin K. This can interfere with warfarin if you eat lots of it. It is best to eat regular small amounts. Cranberry juice can also increase the effects of warfarin and it is important to avoid it, or only drink small amounts, when taking warfarin.
Losing or putting on weight can affect your INR (see Considerations when taking warfarin for more information), so you will need to be weighed regularly.
Interactions with alcohol
It is dangerous to binge drink or get drunk while taking warfarin. Doing this may increase the effect of warfarin and so increase the risk of bleeding.
- Do not drink more than three units of alcohol a day if you are a man or two units a day if you are a woman. It is not safe to save up units to have on one day.
- One unit is roughly equivalent to half a pint of beer or lager or a single measure (25ml) of a spirit such as vodka. A small glass (125ml) of wine is around 1.5 units.
- People with liver disease who are taking warfarin should not drink alcohol.
