What is Warfarin?
Timothy Maly, MD, is a family physician at Berthoud Family Physicians in Berthoud, Colo
Question: What is warfarin?
Answer: Warfarin – one of the most commonly prescribed medications in the country – still might be an unfamiliar word to many people. Its job, though, is to save lives. Many people who have an irregular heartbeat, known as atrial fibrillation, take warfarin.
You might know it by brand names such as Coumadin or Jantoven. Commonly referred to as blood thinner, warfarin is an anticoagulant.
The drug targets and decreases production of certain clotting proteins that are made by the liver. People taking warfarin are trying to prevent the formation of blood clots or treat existing blood clots.
Warfarin was discovered in the 1950s and researched by the Wisconsin Alumni Research Foundation. The chemical warfarin also could be found in a product used to kill rats.
About 45 percent of people who take warfarin have atrial fibrillation or A Fib. When the heart quivers as in A Fib, it is not pumping effectively and blood is not moving around the body to delivering oxygen to all areas. In this condition, a blood clot can form in the heart’s upper chambers (atria). That alone usually isn’t dangerous, but if that clot moves to the brain, it can cause a stroke.
Another 15 percent of people on warfarin take it because they have blood clots in their legs that can travel to the lungs (pulmonary embolus). Those can be fatal. Another 15 percent have had heart valve replacement with a mechanical valve. The synthetic valve requires the patient to take warfarin because they are at increased risk of forming blood clots which can be fatal or cause a stroke.
Other people who take warfarin do so typically because they are at high risk of forming or have blood clots in other parts of their body.
The amount of warfarin a person needs to take varies and can go up and down over time. The dose is determined by blood test called a protime or INR. It’s important to have your blood tested and dosages adjusted accordingly. Taking too much increases a person’s risk for bleeding. Taking too little may increase risk for new blood clots
Most often a patient will see extra bruising, but not overt bleeding. The risk of bleeding can increase if he or she starts taking a new, different medication, gets sick with an infection or follows a poor diet. Also, because vitamin K promotes blood clotting proteins, people who eat foods rich in vitamin K, such as broccoli or spinach, need to monitor their warfarin dose closely if their diet changes in these vitamin K rich foods.
When providers or pharmacists visit with patients about their warfarin, they try to discover if there has been unusual bleeding, signs of blood in the stool or urine, or any signs of new clotting.
Warfarin can be monitored by your primary care physician or cardiologist.
For the first week, a patient new to warfarin should be tested about three times. Then, they can cut back to two times a week for a few weeks. Gradually they will reduce visits to just once a month to make sure blood levels and the warfarin dose are correct.
