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Anticoagulants - Uses, Contraindications, Precautions, and Drug Interaction

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Anticoagulants are medicines that prevent blood clots from forming. To know more about their uses, contraindications, precautions, and drug interactions read below.

Medically reviewed by

Dr. Nagaraj

Published At November 9, 2022
Reviewed AtNovember 14, 2022


Anticoagulants are a group of medications that prevent blood clots from forming in patients at high risk or with preexisting heart and blood vessel diseases. Anticoagulants are often called blood thinners as they break up dangerous blood clots in the heart and blood vessels, which can otherwise lead to heart attack or stroke.

What Are the Different Types of Anticoagulants?

There are three main types of anticoagulant medications that work in different ways to prevent clot formation.

  • Vitamin K Antagonist Anticoagulants - Vitamin K antagonists like Warfarin inhibit the liver from processing vitamin K and suppressing blood clots. These drugs block the function of vitamin K epoxide reductase complex in the liver, leading to depletion of the reduced form of vitamin K.

  • Direct Oral Anticoagulants (DOACs) - Direct oral anticoagulants (DOACs) act faster when compared to vitamin K antagonists. However, they tend to work for a short period and are required to be given twice daily. These anticoagulants include direct thrombin inhibitors (DTI) that work by interfering with the enzyme thrombin that helps in clot formation. They bind directly to thrombin and do not require a cofactor such as antithrombin to exert their effect. Another anticoagulant is direct factor Xa inhibitors (DFXaI) which stop the working of the Xa factor. Factor Xa inhibitors bind selectively and reversibly to the clotting factor Xa. Factor Xa plays an important role in the blood clotting mechanism.

  • Low Molecular Weight Heparins ( LMWH) - Drugs like Dalteparin and Enoxaparin are more long-lasting and are mostly used in hospitals. These anticoagulants help to remove blood clots in the legs and other parts of the body.

What Are Anticoagulants Used For?

Anticoagulants are generally prescribed when there is a risk of developing blood clots that may disrupt the flow of blood in the body or serious conditions such as

  • Stroke or transient ischaemic attacks(TIAs).

  • Heart attacks.

  • Deep vein thrombosis (DVT).

  • Pulmonary embolism.

Anticoagulants may also be prescribed to prevent the above conditions, especially if you have the following:

  • History of blot clots.

  • Post hip or knee replacements.

  • Aortic valve replacement.

  • Atrial fibrillation.

  • Thrombophilia.

  • Antiphospholipid syndrome.

What Is the Difference Between Anticoagulants and Antiplatelet Drugs?

Anticoagulants such as Heparin or Warfarin slow the process of blood clotting or in conditions where there is a risk of clot formation. Antiplatelets such as Aspirin or Clopidogrel prevent platelets from clumping together to form a clot and are usually given to people who have had a heart attack or stroke.

How to Take Anticoagulants?

The medicines should be taken at the same time once or twice a day because the effect of anticoagulants wears off within a day. They can be taken with water and with or without food. It is advised not to skip any dose or take double doses. Anticoagulants are given in oral and injection forms.

What Are the Side Effects of Anticoagulants?

Excessive bleeding is the most common side effect of anticoagulant therapy. It is important to seek medical attention immediately if you notice severe or recurrent bleeding involved in an accident or experience a blow to the head.

This may occur in many ways, including.

  • Heavy menstrual flow.

  • Bloody or discolored urine or feces.

  • Prolonged nose bleeding.

  • Bleeding gums.

  • Vomiting blood.

  • Prolonged bleeding from a cut.

  • Coughing up blood.

Other side effects may include,

  • Indigestion.

  • Dizziness.

  • Diarrhea or constipation.

  • Headaches.

  • Rashes.

  • Hair loss.

  • Itchy skin.

  • Jaundice.

In What Conditions Should You Avoid Taking Anticoagulants?

  • Bleeding - People taking anticoagulants tend to bleed easily, even from minor cuts or scrapes, and should be taken care of when shaving or toothbrushing. Hence, it is advised to take the anticoagulants as directed by the doctor and have regular monitoring.

  • Surgery - The dose and the timings of the anticoagulants may require to be adjusted when you need a surgical procedure as there can be an increased risk of bleeding.

  • Dental Procedures - Invasive dental procedures like tooth extraction or gum surgery have the potential to cause bleeding. Taking anticoagulants such as Warfarin or Clopidogrel may make it difficult to stop bleeding.

  • Pregnancy - Anticoagulants like Warfarin are teratogenic and may increase the risk of fetal anomalies and low birth weight and, therefore, should be avoided when possible during pregnancy.

  • Breastfeeding - Anticoagulants like Apixaban, Dabigatran, and Edoxaban are not recommended safe if you are breastfeeding and should be avoided.

  • Children - Anticoagulants cause bleeding easily and should be given with caution in children and need regular monitoring by the doctor.

  • Kidney Disease - Warfarin may cause renal damage in patients with chronic kidney disease and should be administered with caution in these patients.

  • Peptic Ulcer - Anticoagulants can increase the risk of hemorrhage and active bleeding as should be given with caution. These drugs are associated with an increased risk of gastrointestinal bleeding.

  • Alcohol - High intake of alcohol can increase the risk of hemorrhage (bleeding) and should be avoided when taking blood thinners. Alcohol slows the breakdown of the drug and increases the side effect.

What Drugs Can Interact With Anticoagulants?

Some of the medicines that may affect the anticoagulant and increase the chances of blood clots include

  • Antibiotics.

  • Non-steroidal anti-inflammatory drugs (NSAIDs) such as Aspirin, Ibuprofen, and Naproxen.

  • Antidepressants.

  • Anticonvulsants such as Carbamazepine, Phenobarbital.

  • Rifampin.

  • Sucralfate.

  • Fluconazole.

  • Clarithromycin.

  • Itraconazole.

  • Lovastatin.

  • Metronidazole.

  • Erythromycin.

Foods That Interact With Anticoagulants:

Certain foods, herbal supplements, and beverages may interact with anticoagulants. Vitamin K intake should be consistent in the diet as sudden changes may increase the chances of side effects from Warfarin. Foods and beverages high in vitamin K include

  • Kale.

  • Broccoli.

  • Lentils.

  • Lettuce.

  • Spinach.

  • Cabbage.

  • Cheese.

  • Green tea.

  • Soybean oil.

  • Fish oil.

  • Vitamin E.

You should avoid drinking grapefruit juice, cranberry juice, pomegranate juice, and alcohol.

When Are Anticoagulants Contraindicated?

Some of the absolute contraindications of anticoagulants are

  • Bleeding - The use of anticoagulants is contraindicated in patients with active bleeding or a hemorrhagic diathesis. There can be an uncontrollable hemorrhage or bleeding complications and increased risk during therapy with anticoagulants.

  • Diabetes - Therapy with oral anticoagulants should be administered cautiously in patients with severe diabetes because there may be an increased risk of hemorrhage. The INR should be monitored closely and should be advised to report any signs of bleeding.

  • Hypertension - The use of anticoagulants is contraindicated in patients with severe, uncontrolled hypertension. Anticoagulants may predispose the patient to hemorrhage.

  • Liver Disease - Oral anticoagulants are metabolized by the liver. Patients with hepatic impairment have decreased clearance of the drug.

  • Protein C Deficiency - Therapy with oral anticoagulants should be administered cautiously in patients with a known deficiency in protein C as it increases the risk of hypercoagulation.

  • Decreased Response - Patients with edema, hereditary coumarin resistance, or hyperlipidemia exhibit hypothrombinemia response to oral anticoagulants. These patients should be monitored and dosage adjustments may be required.

  • Renal Dysfunction - Patients with renal impairment may have an increased risk for bleeding and should be closely monitored. These patients may require dose adjustments.


Anticoagulants are drugs that inhibit blood clots from forming in the blood vessels of the body. These medicines have life-saving potential and can be extremely helpful. The side effects of anticoagulants can be serious and life-threatening and should be taken as instructed by the doctor.

Frequently Asked Questions


To Whom Are Anticoagulants Prescribed?

Anticoagulants are drugs used to manage blood clots as they have a tendency to reduce blood thickness. Blood thinners are prescribed for patients with a high risk of stroke, heart attacks, deep vein thrombosis, high blood pressure, etc.


What Is Considered To Be a Natural Anticoagulant?

There are factors in the blood that act as natural anticoagulants. These agents are present in the blood to make the blood flow easily without clotting. Some of the natural factors are protein C, protein S, and antithrombin.


What Is Considered the Most Safest Anticoagulant?

Apixaban is the safest oral anticoagulant drug compared with Warfarin (one of the most commonly used anticoagulants), as Apixaban shows minimal risks of major complications like bleeding in the brain or the tract of the stomach.


Which Is the Most Preferred Anticoagulant for Treating Blood Clots?

Warfarin is the most commonly preferred drug of choice for oral anticoagulants. However, there are newer anticoagulants available in the market and is also very good at managing blood clots; they are:
- Rivaroxaban.
- Dabigatran.
- Apixaban.
- Edoxaban.


To Whom Are Anticoagulants Contraindicated To Use?

- Anticoagulants should be avoided in patients with the following medical conditions, and they are,
- Patient with active bleeding injuries.
- Coagulopathy (a bleeding disorder in which a patient's blood has the inability to clot).
- Patients who have undergone major surgeries recently.
- Acute brain bleed.
- Major traumatic injuries.


Which Anticoagulant Causes the Highest Bleeding?

The anticoagulants that are very potent and cause increased bleeding are:
- Oral Warfarin.
- Nonvitamin K antagonists like Rivaroxaban, Dabigatran, Apixaban, and edoxaban.
- Injectable anticoagulants like low molecular weight heparins.


What Are the Considerations To Keep In Mind While Taking Anticoagulants?

There are a few important considerations to be informed the doctor about when or before taking anticoagulant medications, and they are:
- If the patient is planning for surgery.
- If the patient is pregnant.
- If the patient is breastfeeding.
- If the patient has any bleeding disorders
- If the patient is under any medications like steroids, antibiotics, or antidepressants that might interact with anticoagulants


What Are the Clinical Features of Blood Thinning?

The clinical features of thinning of blood can b seen by the following symptoms, and they are:
- Delayed blood clotting in a wound.
- Bleeding gums.
- Nosebleeds.
- Pronounced menstrual bleeding.
- Blood in stools.


What Are the Foods That Naturally Thin Down the Blood?

Intake of vitamin E-rich foods can naturally thin the blood, and some of the foods that thin the blood naturally are more water, cinnamon, ginger, turmeric, ginger, cayenne peppers, grape seed extracts, ginkgo Biloba, ginseng, feverfew, pineapples, aloe vera, and evening primrose.


What Are the Diseases Thinning Blood?

Diseases that cause major destruction of the white blood cells thus reducing the platelet count, cause excessive bleeding. Some of the diseases that cause this are
- Hepatitis C.
- Mumps.
- Rubella.
- Dengue. 


Can Taking Anticoagulants Be Risky?

Yes, taking anticoagulants can be risky; oral anticoagulants are termed high-risk medications and can potentially cause profuse bleeding. And hence it is important to take anticoagulants on the prescription of a doctor under a controlled allowance.


Can Walking Help in Managing Blood Clots, and How Can We Eliminate Them?

In General, studies have shown that an overall increase in physical activity can help dissolve blood clots. This shows a brisk walking of 30 to 45 minutes for five to seven days per week can certainly improve eliminating the clots.


What Can Be Done To Thicken the Blood in a Shorter Time?

Blood can be thicked by an increased intake of vitamin K-rich foods as they are fat-soluble vitamins and natural coagulants responsible for the clotting of blood. Some of the foods that thicken the blood are:
- Meat and seafood.
- Beans and legumes.
- Grains and cereals.
- Increased salt intake
- Iron-rich fruits and vegetables.
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Dr. Nagaraj
Dr. Nagaraj



anticoagulant therapy
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