Many medications may change the anti-clotting action of warfarin. This includes medicines prescribed by your doctor, and items you can buy without a prescription from your pharmacy, supermarket or health food store.

Assume that any medicine can affect warfarin unless advised otherwise by your doctor or pharmacist.

To minimise the risk of having a problem with your warfarin:

• Check with your doctor or pharmacist before starting or stopping any medicines.
• Tell the pharmacist you are taking warfarin before purchasing any 'over the counter' medicines.
• Ask your pharmacist before buying any vitamins, herbal or natural supplements.
• If you visit a different doctor, or see a dentist, be sure to tell them you are taking warfarin.
• Wear a MedicAlert^® bracelet or carry a card in your wallet identifying that you take warfarin. (More information on MedicAlert^® bracelets can be found at www.medicalert.com.au. A warfarin identification card for you to fill in is available here)

Aspirin also affects blood clotting and small doses of aspirin are used to stop heart attacks and strokes. If you are already taking aspirin when you start warfarin, check with your doctor whether you need to keep taking it. There are some conditions where people will need to take a combination of medicines that affect how their blood clots, for example some people may need to take aspirin and warfarin together, while in other conditions people may only need one or the other.

Aspirin in larger doses is used to treat pain and fevers. It is best to avoid larger doses of aspirin while taking warfarin. For pain or fever, paracetamol is safer than aspirin as long as it is used at the recommended dose. Check with your healthcare professional if you need treatment for long-term pain.