Warfarin: An Oral Anticoagulant Medication
Warfarin (Coumadin) decreases the blood clotting tendency by interfering with blocking the body's blood clotting substances. There are other anticoagulants besides warfarin — your cardiologist will decide which one is right for you.
What do I need to know about Warfarin?
- Warfarin can increase your risk of serious bleeding problems, even when the dose is at the recommended level.
- Carefully and regularly monitor your body’s response to the medication.
- Understand any limitations your healthcare provider recommends. If you take warfarin, you may need to limit some physical activities to reduce the chance of injury that can cause bleeding, particularly a head injury.
- If you’re a woman of child-bearing age, communicate your reproductive plans to your healthcare provider as using warfarin during pregnancy can cause malformations in an unborn child. Discuss the risks of this medication with your doctor before you get pregnant.
If you're taking warfarin, your doctor will regularly monitor the blood-clotting level to be sure your dosage is correct. A value called the INR (international normalized ratio) tests how quickly your blood clots. Your warfarin dosage will be carefully adjusted to maintain an INR level appropriate for your heart condition. You must take your medicine exactly as prescribed. You also must have your blood tested regularly according to your doctor's orders. Read more about monitoring your PT time.
Medication Interactions and Your Labwork
Many over-the-counter or prescription medicines can interact with warfarin and change your INR, which can be hazardous.
These medicines include:
- Most antibiotics,
- Several pain medicines (e.g., non-steroidal anti-inflammatory drugs)
- Medications for acid reflux such as cimetidine (Tagamet)
If you're taking warfarin and start a new prescription or over-the-counter medication, check with your doctor. It's important to determine if this might affect the INR and if you need more frequent blood testing.
If I'm on warfarin, is it okay to take aspirin for a headache?
In general, avoid aspirin when you're being treated with warfarin unless you’ve been specifically directed to take it. For example, if you have a mechanical heart valve, low-dose aspirin may be added to warfarin to help prevent blood clots from forming. Discuss this with your cardiologist or the doctor who is caring for you.
Certain foods also interfere with how your body processes warfarin. If you're on warfarin, always ask your doctor about your diet and before taking any other medicines, including vitamins and herbal preparations.
If I end up needing to have surgery or a catheter ablation, should I plan to stop my warfarin?
Warfarin is long-acting, lasting several days after you stop taking it. In contrast, the NOACs are cleared from your body much sooner, usually in a day or two. If you need elective surgery (including dental surgery), your normal anticoagulant may be stopped and you may be given heparin or low-molecular-weight heparin (Lovenox), which act rapidly to thin the blood. When stopped, the effect also wears off rapidly. These medications can be injected just under the skin (subcutaneously) or given intravenously.
This is often referred to as "bridging". Your doctor will decide if bridging is necessary. If you are having a catheter ablation, your doctor may decide to leave you on warfarin or a NOAC, or may bridge you.