Coumarin (warfarin) is a blood-thinning drug that works by inhibiting the function of vitamin K, which is an important factor in the formation of blood clots in the body.
Coumarin and Stroke
Coumarin is a powerful medicine used to prevent strokes. Coumarin has powerful blood-thinning properties (ie, it prevents the abnormal formation of blood clots in the body). An example of a disorder where abnormal blood clot formation leads to a stroke is atrial fibrillation, a disorder in which the heart beats erratically causing unwanted blood clots to form in the chambers of the heart. Other conditions in which coumarin is used to prevent stroke include:
- When someone surgically replaces a defective heart valve with a mechanical prosthetic valve.
- When someone is found to have a blood clot in their heart after a heart attack.
- When a deep vein thrombosis in someone’s leg is found (also called deep vein thrombosis or DVT. DVT can cause stroke in people with small holes on the left and right sides of the heart. This small hole is called a patent foramen ovale or PFO.
- When someone has an abnormal tendency to form blood clots due to an autoimmune disease such as lupus.
- When someone has a genetic predisposition to form blood clots due to a lack of one or more body mechanisms that normally prevent abnormal blood clots from forming.
International Normalized Ratio (INR)
Blood coagulation is measured using the International Normalized Ratio (INR), which attributes 1.0 to a person with normal thrombogenic capacity. When people took coumarin, their INR increased, suggesting they were less likely to develop blood clots.
The ideal INR for stroke prevention is between 2-3, but this range may vary depending on the disease being treated. INR is measured with a blood test. If the INR is too high (over 3), unnecessary bleeding may result. This is why people taking Coumadin must have their blood drawn every few weeks or months.
blood pressure control
People who have high blood pressure and are taking coumarin to prevent stroke must always keep in mind that high blood pressure increases the risk of hemorrhagic stroke or stroke caused by cerebral hemorrhage. Because coumarin reduces the body’s usual mechanism to stop bleeding, people taking coumarin must keep their blood pressure under control at all times.
- Only take medicines prescribed by your healthcare provider (coumarin interacts with many medicines).
- Take coumarin at the same time each day (usually at bedtime).
- Eat the same amount of foods containing vitamin K (such as fish, broccoli, spinach, cabbage, kale, cauliflower) every day.
- Avoid excessive drinking.
- Avoid activities that could cause you to fall.
- Never stop Coumadin without your practitioner’s knowledge.
- Never take a double dose of coumarin unless specifically asked by your healthcare provider.
- Call your doctor if your stool changes color.