Warfarin is one of the drugs in the group of anticoagulants derived from coumarin, a natural aromatic substance that is used as a fragrance for cosmetics and food. Warfarin works to prevent blood clots that prevent the continuous flow of blood throughout the body.

It should be noted that veins and arteries are part of the pulmonary and circulatory system, both allow continuous and normal flow of blood. Therefore, a certain degree of clotting in the veins is necessary to contain bleeding when there is an injury, but excessive clotting can lead to serious complications.

What is warfarin and what is it for?

Warfarin is an anticoagulant derived from coumarin, a substance that acts against blood clotting and can be administered long-term.

This substance is directly related to vitamin K, and serves to slow clotting and reduce the risk of a blood clot within a blood vessel or the heart. On artificial surfaces it acts as compensation for material, such as artificial heart valves. These are the most indicated uses:

Warfarin is used to treat thrombosis

This medicine is used to prevent and treat deep vein thrombosis or blood clots in the veins of the lower extremities and pulmonary embolism (blocked artery when a blood clot in the lungs)

Warfarin works for cardiac arrhythmia

Blood clots that occur during cardiac arrhythmia, cause difficulty in the speed or rhythm of the heart palpitations. A condition that is fought with warfarin.

Warfarin in implantation of artificial mechanisms

Warfarin is used to prevent blood clots after implantation of artificial heart valves.

Warfarin for dental treatments

These treatments can usually be done without warfarin anticoagulation therapy. However, it is always advisable to contact the dentist before a planned check-up or dental treatment to allow a blood clotting test to be performed in time.

Warfarin serves as a rodent poison

Warfarin and similar substances are also used as rat poison: the rodent when dying will die of internal bleeding. For this reason, caution should be exercised when warfarin is administered in patients at increased risk of bleeding, for example, in people with a gastric ulcer or after a stroke.

How does warfarin work?

Warfarin does not thin the blood, as is sometimes incorrectly claimed, but rather works by blocking the effect of vitamin K found in the body, among other things, necessary for the formation of clotting factors, or substances that they are involved in this process. Higher doses of warfarin can cause bleeding, so it is extremely important to take this medicine exactly as your doctor recommends.

How to take the dose of warfarin?

The warfarin dose is usually given once a day, preferably at the same time each day. This dose is individual and is determined by a doctor.

As in most medicinal indications, forgotten doses can be resumed within 12 hours. In case of exceeding more than 12 hours, do not take the forgotten dose, in that case, continue with the indicated treatment.

In case of forgetting more than one dose, it is important to notify the specialist to readjust the treatment. You should never take a double dose or two doses in a short sequence.

If an extra dose of the medicine is accidentally taken or the usual dose has been significantly exceeded, the doctor should also be informed.

Warfarin overdose and its treatment

For therapeutic purposes, in periodic blood coagulation tests, the INR (International Normalized Ratio) value is generally between 2 and 3, in some indications between 2.0 and 3.5 or 2.5 and 3.5. Therefore, at a lower INR, the warfarin dose should be increased and vice versa.

Values ​​greater than 4 already indicate an overdose with an increased risk of bleeding complications. If a significant warfarin overdose occurs, the drug needs to be temporarily stopped. In the case of more severe bleeding, the blood plasma or clotting factor concentrate can be practically canceled immediately.

Administration of vitamin K leads to a more sustained reduction in the effect of warfarin, but this effect will only develop after several hours.

Fat-soluble vitamin K is an interesting factor in warfarin therapy that can be counted on. Mainly because it plays a double role.

Side effects of warfarin

The most serious side effect of warfarin is bleeding. The risk of bleeding increases when the INR increases.

On the other hand, if any of the following symptoms appear, it is necessary to contact the doctor immediately:

  • Nose bleeding for more than 10 minutes
  • Blood in the urine or black stools
  • Excessive bruising with no apparent cause
  • Vomiting blood
  • Unusual headaches
  • Abnormally heavy bleeding or vaginal bleeding outside of the menstrual cycle

Interactions with Warfarin

Warfin and alcohol

Avoid drinking alcohol excessively with a maximum of one alcoholic drink per day, that is, 20 – 30 g of alcohol (0.5 l of beer, 2 tablespoons of wine, 0.5 dl of distillate). However, it will always depend on the general state of health, which is why the endorsement of the doctor on the consumption of alcohol is necessary.

Warfin and vitamin K

On the contrary, the most important factor that reduces the effect of warfarin is the high consumption of vitamin K through food.

Iron, magnesium, zinc, charcoal: can form bonds with warfarin and reduce its absorption, therefore, take at least two hours before taking warfarin or two hours after.

St. John’s Wort: reduces the effect of warfarin and some other medications. During warfarin treatment, drinking St. John’s wort and other herbs should be avoided until a doctor’s visit is made.

Probiotics: normally found in dairy products and other foods, which can increase the natural synthesis of vitamin K in the intestines, reducing the effect of warfarin, however, this effect is not significant.

Grapefruit, grapefruit juice: a single intake has no effect on warfarin, but regular consumption may increase the effect of warfarin in some people.

Protein concentrates used by athletes to increase muscle mass can significantly reduce the effect of warfarin as the albumin (the protein) to which warfarin binds increases.

Food supplements: These products usually contain vitamin K or other active substances that can interact with warfarin, so they should be avoided, or a doctor should be consulted about the use of a particular product.

It is important to mention that vitamin K is essential for the formation of natural anticoagulant factors whose deficiency leads to an increased risk of blood clot formation.

This vitamin works in the blood clotting process in a dual and contradictory way to prevent clotting. For health, the balance of these events is essential, and this goal must be taken into account when determining the dose of warfarin.

In conclusion, warfarin is an excellent anticoagulant

All problems related to blocked blood flow completely affect the entire body. In this case, warfarin is an excellent alternative to alleviate risks and related bothersome symptoms. However, it is necessary to inform the treating physician of any situation, diseases and other prescribed medications, to avoid interference with warfarin, since any factor is determining to achieve the expected results.

Samantha Robson
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Dr. Samantha Robson ( CRN: 0510146-5) is a nutritionist and website content reviewer related to her area of ​​expertise. With a postgraduate degree in Nutrition from The University of Arizona, she is a specialist in Sports Nutrition from Oxford University and is also a member of the International Society of Sports Nutrition.

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