Warfarin - (Coumadin®)
This blood-thinning drug is often used to treat and prevent blood clots and conditions related to them, such as atrial fibrillation or heart attack. A very common medication, warfarin is prescribed millions of time each year. Yet its use often starts with trial and error.
For this drug to be safe and effective, warfarin doses need to be personalized. With too much of the drug, some people experience dangerous bouts of bleeding, while for others, too little medication may lead to harmful blood clots. Should you need warfarin, your genetic results can help you and your doctor reduce your risk of such complications.
Warfarin belongs to a group of drugs called vitamin K antagonists, and can be given either as a liquid through an IV or taken as a pill.
Your Results
Likely to require customized dose
Your genetic results indicate that a customized warfarin dose is likely to be most effective for you. Should you need warfarin treatment, share your genetic results with your doctor to help calculate the right dose for you. You can find your genetic results on the Your DNA page.
Facts about warfarin and warfarin sensitivity
Generic name:
warfarin (WAR-far-in), warfarin sodium
Brand names:
Coumadin®, Jantoven®, Lawarin®, Marevan® Waran®
Primary uses:
Warfarin is prescribed to prevent blood clots in a variety of conditions, including atrial fibrillation, deep vein thrombosis (DVT), pulmonary embolism, the presence of artificial heart valves, and, occasionally, after heart attacks.
Side effects:
The most serious problem related to warfarin sensitivity is excessive bleeding. Other common issues include abdominal cramping and excessive bruising.
Sensitivity to warfarin usually varies greatly from person to person, and finding the correct warfarin dose for any individual is complicated. The medication’s blood thinning activity has to be monitored by frequent blood testing to ensure that the dose given is adequate yet safe. In addition, warfarin can interact with many commonly used medications, and even with some foods, such as cranberries.
Warfarin dosing:
Given how complicated it is to find the correct warfarin dose for any one individual, the process often begins with trial and error. Knowing your genetic results can reduce the time it takes to find your correct dose.
If you are taking warfarin, your doctor will conduct regular blood tests to ensure that the dose you are taking is high enough to prevent blood clots, while remaining safe. Your blood will be tested to determine its clotting ability, measured by a standard called the International Normalized Ratio (INR). In the What You Can Do section, you'll learn more about how your doctor calculates your INR.
Learn more about how this drug affects youWhat you can do
This information is likely to be important for your health:
- Let your doctor(s) know about this genetic result.
- Carry this information with you in case it is needed in a medical consultation or emergency
- Consider sharing this information with your family.
- If you are already taking warfarin, don’t try to use your genetic results to make changes to your medication on your own. Instead, talk to your doctor right away.
According to suggestions from the U.S. Food and Drug Administration, genetic variants are one of several factors that your doctor may want to take into account when prescribing warfarin.
Based on your genetic results, a customized warfarin dose is likely to be most effective for you. If you need drugs to treat or prevent blood clots, only your doctor can calculate your personalized dose safely, using both your genetic results and other factors (such as your height, weight, and other medications you may be taking) to help maximize warfarin benefits while minimizing side effects.
Learn more about what you can doHow common are these side effects?
About 20 percent of people receiving anti-clotting medication, such as warfarin, experience a major or minor bleeding event afterwards. More minor side effects can include excessive bruising and bleeding, stomach cramping, nosebleeds, and blood in the urine or stools. (These numbers reflect past occurrences of warfarin side effects in the general population, not your personal genetic risk, and include people of all ancestries).
Genetics is only part of the story. Your age, gender, weight, diet, and other medications are all factors that should be taken into account to determine the safest and most effective warfarin dose for you.
Learn more about side effects