Warfarin sodium (
Coumadin®,
Jantoven®) is a prescription anticoagulant, often described as a "blood thinner" (although it does not actually thin the blood). It is used to prevent and treat blood clots due to various causes.
Just like any medicine, warfarin can cause side effects, which can be quite dangerous. The risk of most dangerous side effects can be reduced by careful monitoring.
Possible warfarin side effects include but are not limited to:
- Bleeding, including dangerous internal bleeding
- Easy bruising
- "Purple toe syndrome"
- Hair loss.
(Click Side Effects of Warfarin to learn more, including potentially serious side effects you should report immediately to your healthcare provider.)
What Should I Tell My Healthcare Provider?
You should talk with your healthcare provider prior to taking this medication if you have:
- A bleeding disorder
- Intestinal or stomach ulcers or bleeding
- Bleeding in the brain
- An aneurysm
- Inflammation of the sac the surrounds the heart (the pericardium)
- A bacterial infection of the endocardium (the inner layer of the heart)
- A condition (such as a mental illness) that limits the ability to follow instructions carefully
- Had a negative reaction to heparin
- Liver disease, such as liver failure, cirrhosis, or hepatitis
- Kidney disease, such as kidney failure
- High blood pressure
- A clotting disorder known as protein C deficiency
- Polycythemia vera (a condition involving excess red blood cells)
- Vasculitis (a blood vessel disorder)
- Diabetes
- An indwelling bladder catheter
- Any allergies, including allergies to food, dyes, or preservatives.
Also, let your healthcare provider know if you:
Make sure to tell your healthcare provider about any other medications you are taking, including prescription and non-prescription medicines, vitamins, and herbal supplements.
Blood clotting is a complex process that involves many different substances in the body, known as clotting factors, and several different steps. Warfarin works to inhibit blood clotting by decreasing the formation of active forms of certain clotting factors.
Some clotting factors require vitamin K to be converted into their active forms. Although this reaction changes vitamin K into an unusable form, the body can recycle it back using an enzyme known as vitamin K epoxide reductase. Warfarin blocks this enzyme, inhibiting the recycling of vitamin K and, thereby, decreasing the formation of the active clotting factors.
It is important to understand that warfarin does not "dissolve" or break down blood clots (only special "clot buster" medications that must be given in the hospital can do this). Rather, it prevents them from forming. When used to treat a blood clot, warfarin keeps the clot formation in check, allowing the body's natural processes to break down the clot.
When and How to Take This Drug
General considerations for those taking warfarin include the following:
- This medication comes in tablet form. It is also available as an injection, although this form is rarely used.
- Warfarin is usually taken by mouth once a day.
- Although it does not matter what time of day you take warfarin, be sure to take it at the same time each day.
- If necessary, the tablets can be broken in half. However, it is best to avoid this, since even tiny variations in the dosage can cause problems.
- You can take this medication with food or on an empty stomach.
- For warfarin to work properly, it must be taken as directed.
The recommended dose of warfarin will vary, depending on how you respond to the medication (this is monitored using regular blood tests). As is always the case, do not adjust your dose unless your healthcare provider specifically instructs you to do
People who take warfarin must follow certain dietary restrictions, as some foods interact with this medication
(see Coumadin Diet for more information).
What If I Take an Overdose of Warfarin?
An overdose of warfarin could potentially cause life-threatening problems as the result of dangerous internal bleeding. If you happen to take too much of this drug, seek immediate medical attention.
How Should the Medication Be Stored?
Warfarin should be stored at room temperature, away from moisture and heat. Keep this and all other medications out of the reach of children.
What Should I Do If I Miss a Dose?
If you do not take your warfarin as scheduled, take your missed dose as soon as possible on the same day. However, do not take two doses on the same day or take a double dose. Be sure to keep track of any missed doses (perhaps on a calendar), as your healthcare provider will use this information when monitoring your response to the medication.
If you miss one or more doses, be sure to contact your healthcare provider for further instructions.
Brand-name warfarin (
Coumadin,
Jantoven) is manufactured by Bristol-Myers Squibb Company. Generic versions are made by various manufacturers.
- Warfarin 1 mg
- Warfarin 2 mg
- Warfarin 2.5 mg
- Warfarin 3 mg
- Warfarin 4 mg
- Warfarin 5 mg
- Warfarin 6 mg
- Warfarin 7.5 mg
- Warfarin 10 mg.
An injectable version of warfarin is also available.
