Warfarin, Coumadin is an anticoagulant used to prevent and treat blood clots (especially deep vein thrombosis – DVT or pulmonary embolism – PE). Preventing formation of blood clots helps to reduce the risk of a stroke or heart attack. The active ingredient is warfarinum natricum. You can come across other brand names such as Coumadin, Marevan, Jantoven, Lawarin and Uniwarfin.
There are several condition that may increase your risk of developing blood clots:
- Irregular heart rhythm (atrial fibrillation)
- Heart valve replacement
- Recent heart attack
- Certain surgeries (such as hip/knee replacement)
- Acquired or congenital changes in the coagulation system – Thrombophilias
Warfarin is an anticoagulant, often called as a “blood thinner”. By decreasing the amount of certain substances (clotting proteins), Warfarin helps to keep blood flowing smoothly in your veins.
Side effects of Warfarin, Coumadin
Warfarin can cause serious even possibly fatal bleeding. This can happen especially when you just started taking this medication, if you take too much of warfarin or together with some other medicines that increase the effect of Warfarin. If you are taking warfarin then you should be aware that certain medications, natural supplements and foods can affect the levels of warfarin in the blood and can cause serious complications.
Your doctor will monitor closely your lab results (INR test) to decrease your risk of bleeding.
Warfarin has a “narrow therapeutic range.” This means that any change in the amount of warfarin in the blood may change the way warfarin works for you. For example, too much warfarin can cause excessive bleeding, while too little could affect the ability of the drug to prevent the formation of clots, and this could lead to serious health consequences such as heart attack or stroke.
Some drugs (both with prescription and without), natural health products (for example, herbal remedies, vitamins, and supplements), and even certain foods, are known or suspected to interact with the warfarin in a manner that changes the level of drug in the blood. For this reason, people who take warfarin should be very cautious when considering the use of these products.
How does Warfarin work?
Warfarin belongs to a group of oral anticoagulants. It acts as an antagonist of vitamin K, thereby prolongs the process of blood clotting. It is presented in various packages and color-coded tablets according to the content of milligrams – 5 mg pink, blue 3mg and beige 1 mg. But never rely only on color, but always check the information on the packaging of the drug!
Warfarin is absorbed from the stomach immediately, however, for the full onset of action it takes about 3-5 days after the first dose. The effect of warfarin last about the same time after discontinuation.
Other possible side effects include nausea, vomiting, diarrhoea, abdominal cramps, fever. It can also lead to more or less bleeding or bruising.
Interaction with Warfarin, Coumadin
Many prescription and OTC medications are known to interact with warfarin. Examples of such drugs from various classes include, but are not totally limited to the following:
- Antibiotics (azithromycin, erythromycin, tetracycline)
- Acetylsalicylic acid, Aspirin – if your doctor wants to prescribe this, inform him that you are taking warfarin. There is a combination therapy Warfarin + Aspirin, but in this case the doctor will proportionately reduce the dose of warfarin. It is also important to monitor your INR more frequently. Never take Aspirin without consulting with your doctor and always notify your doctor that you are taking Warfarin. Be careful if you visit more doctors who prescribe drugs. It can happen that doctor might miss the important information that you are already taking warfarin. So it is the patient who has to carefully collect information on drug interactions and warn doctors about current medications.
- Paracetamol (acetaminophen) – Paralen – beware: even Paracetamol can have harmful effects. Acetaminophen increases the risk of bleeding, particularly if you take 2 g or more per day. It is still safer than Aspirin, but should be limited to lower doses and you should frequently check the level of INR.
- Nonsteroidal anti-inflammatory agents – celecoxib
- Antidepressants (fluoxetine, paroxetine, sertraline)
- Antiulcer drugs and antacids (cimetidine, omeprazole, ranitidine)
- Lipid lowering agents (fibrates, statins, such as lovastatin and simvastatin)
- Antifungal agents (itraconazole)
Your doctor or pharmacist should advise you of the drug interactions. The desired level of warfarin in your blood is influenced by food supplements, illness or certain foods. More about food, which to avoid and what is the warfarin diet.
How to minimize the risks of Warfarin, Coumadin?
- Tell your doctor about all other medicines, food supplements, vitamins and herbs you take
- Take the dose of warfarin each day at the same time (tip: if you forgetting often, get the dispenser for medications or check each day in the calendar that you took your dose)
- Take regular blood clotting tests INR
- Talk to your doctor always before you start taking any new medications and / or natural products etc., because your dose of warfarin may need to be adjusted
- If you are already taking medications and / or natural health products along with warfarin, do not change the routine, if you talked about it with your doctor
- Ask your doctor about foods that may alter the effects of warfarin or have a direct effect on blood clotting
- If you eat or drink foods that may alter the effects of warfarin, make sure that the amounts of these foods have been about the same every day – i.e. if you eat a salad, eat it every day, the same amount and do not abruptly change your eating habits or the amount consumed
When to seek medical help?
If one of the following symptoms occur, you must contact your doctor immediately:
- Unusual feeling of weakness or fatigue (symptoms of anemia)
- Bleeding after trauma continues even 10 minutes after treatment
- Coughing or vomiting blood (even if it looks like ground coffee )
- Bleeding from the nose, gums or ears
- Urine or stool has an unusual colour
- Spontaneous bruising
- Extremely heavy menstruation
- Worsening fever or illness
- Painful fall or hit to the head
- Unusual pain or swelling
- Difficulty breathing
Warfarin, Coumadin should not be used in pregnancy because it has adverse effects on fetal development (see warfarin embryopathy). During pregnancy warfarin is used only in exceptional situations. Your doctor will consider whether the benefits outweigh the risks. Otherwise, low molecular weight injection is used instead of warfarin when women are planning to get pregnant and during whole pregnancy.