Anticoagulant drugs



Anticoagulants are drugs that help prevent clots from forming inside blood vessels (veins and arteries).

Clots are clots of blood resulting from the clotting process that normally occurs when a blood vessel is injured, such as when getting a wound, to stop blood from flowing out. The formation of a clot in the damaged vessel allows, in fact, to seal the lesion through a "hemostatic plug" which stops the bleeding.

Clots are therefore a protective mechanism, but when they form at the wrong time and place, they can clog blood vessels and prevent blood from reaching organs such as the brain, heart and lungs with serious and dangerous consequences for health. .

Anticoagulants, often mistakenly referred to as "blood thinners," do not thin the blood, but significantly inhibit the process that leads to clotting. Like the fluidifiers proper, that is, the antiplatelet agents (such as low-dose aspirin and clopridogel), anticoagulants are used in cases with a high risk of clot formation to reduce the chances of developing serious conditions such as stroke and "heart attack.

Types of anticoagulants

There are different types of anticoagulants, with different characteristics and mechanisms of action.

Some are available in the form of tablets or capsules to be taken by mouth (orally), others, such as heparin, are given through subcutaneous injections or infusions into a vein (intravenously).

These pages contain general information on warfarin (which has been the drug of choice in oral anticoagulant therapy for decades) and new oral anticoagulants (NAOs), including the following active ingredients:

  • rivaroxaban
  • dabigatran
  • apixaban
  • edoxaban

For more detailed information on individual drugs, refer to the AIFA Drug Database, which can be consulted by drug name or active ingredient.

When using anticoagulants

Anticoagulants are used in people with a high risk of clot formation that could block a blood vessel and interrupt normal blood circulation, depriving cells and tissues of the oxygen necessary for their functioning.

Depending on their location, clots can cause the following serious conditions:

  • stroke, which occurs when a clot prevents normal blood supply to the brain causing brain cell death, possibly with permanent disabilities and sometimes fatal
  • transient ischemic attack o TIA (from the English Transient Ischemic Attack), a "mini stroke" that resolves spontaneously within 24 hours, usually without permanent brain damage
  • heart attack (myocardial infarction), which occurs when a clot completely obstructs a blood vessel that carries blood to the heart, depriving it of oxygen, with consequences of varying severity, sometimes fatal
  • deep vein thrombosis, due to the formation of a clot in a deep vein of the body, usually in the legs, resulting in local pain and swelling
  • pulmonary embolism, which occurs when a clot blocks a blood vessel in the pulmonary circulation, cutting off the blood supply to the lungs

Anticoagulants are prescribed to reduce the likelihood of these conditions developing in the presence of the following risk factors:

  • previous episodes of inappropriate clot formation
  • surgical interventions involving prolonged immobilization, such as hip or knee replacement operations
  • implantation of heart valve prostheses, on the surface of which clots can form
  • atrial fibrillation, a type of abnormal heart beat (arrhythmia) which can cause blood clots to form
  • conditions that predispose to clot formation (thrombophilia), such as the presence of factor V Leiden (genetic mutation of coagulation factor V)
  • antiphospholipid antibody syndrome, an immune system disorder that mistakenly attacks fats and proteins in blood vessels, causing abnormal clotting

Anticoagulants can also be used to prevent existing clots from enlarging, assuming proportions that do not allow the body to dissolve and reabsorb them naturally. They are therefore indicated for the treatment of diseases such as deep vein thrombosis and pulmonary embolism.

The duration of therapy depends on why the anticoagulants were prescribed. It can be short-term, such as when undergoing major orthopedic surgery on the lower limbs, or it can continue for life, if you suffer from a chronic disease that predisposes to clot formation.

How oral anticoagulants are taken

Oral anticoagulants are available in the form of tablets and capsules to be taken with a little water, at regular intervals, in one or two daily doses, depending on the active ingredient used.

It is of fundamental importance to scrupulously respect the doctor's instructions regarding the time of intake (in the morning and in the evening in case of double administration), as some anticoagulants exhaust their effects within 24 hours.

People with memory problems or physical disabilities must be assisted during the preparation of the doses to be taken, especially if the tablets are divided, to avoid errors that could compromise the efficacy of the therapy or cause the appearance of even serious side effects.

Whatever active ingredient you use, it is important never to change the dosage of the drug on your own initiative or to discontinue therapy without doctor's advice.

Missed administration or overdose (overdose)

The behavior to be followed in these cases varies according to the situation and the type of drug taken. Therefore, in case of doubt, it is advisable to consult the package leaflet included in the package of the medicine or contact your doctor to find out what to do.

Dose monitoring


Warfarin therapy requires the execution of periodic blood samples to measure the clotting speed, through the prothrombin time (PT) test, the result of which is expressed with a universal reference value, the so-called INR (from " English International Normalized Ratio).

INR values ​​should be checked regularly to ensure that blood does not clot too fast or too slowly for the efficacy and safety of therapy.

The warfarin dosage will be adjusted until the INR values ​​reach the correct range, called the therapeutic range.

In the initial phase of therapy it will be necessary to undergo close blood tests, within a few days of each other.As soon as the INR values ​​have stabilized within the therapeutic range, it will be possible to establish the optimal dose of the drug and the controls can be reduced, up to a monthly sampling.

People who are unable to walk or be transported by the usual means can ask for a collection at home with a "referral from the attending physician in which the reason for the request is indicated.

For some years, portable coagulometers have been put on the market, which allow you to check the INR with a blood sample from the fingertip, through a special lancing device, just like it happens to measure blood sugar in diabetic people. These are rather expensive instruments. for which there is no reimbursement by the National Health Service, their use is also not suitable for everyone and requires a specific training course.

New oral anticoagulants (NAOs)

The use of the new oral anticoagulants (NAOs) does not require constant monitoring of the INR, nor dosage adjustments. It will, however, be necessary to undergo periodic visits to the doctor who will assess whether you are taking the recommended dose of the drug and the possible occurrence of unwanted effects.

Undesirable (side) effects of oral anticoagulants

Oral anticoagulants, like all medicines, can cause unwanted (side) effects.

Since anticoagulants delay the normal blood clotting process, the most common side effect is excessive bleeding (haemorrhage).

Excessive bleeding

Signs of possible ongoing bleeding that need to be watched for include:

  • presence of blood in the urine, which appear colored in pink or deep red
  • stool streaked with red blood I live or black (like coffee grounds) and tarry
  • prolonged bleeding from the nose (lasting more than 10 minutes)
  • bleeding from the gums
  • vomiting of blood or coughing up blood
  • strong pain sudden in the back
  • menstruation longer or more abundant than usual, in women of childbearing age, or other forms of bleeding from the vagina

In the presence of these signs or other episodes of copious, frequent or unstoppable bleeding, it is essential to immediately contact the treating doctor or go to the nearest emergency room. Likewise, it is necessary to undergo an immediate medical evaluation in the event of a serious traffic accident or severe head injury, even in the absence of visible damage.

Other side effects

In addition to excessive bleeding, oral anticoagulants can cause other side effects, which vary according to the active ingredient used.

The specific side effects of each anticoagulant are reported in the package leaflet included in the package of the medicine.

In general, possible side effects other than bleeding include:

  • diarrhea or constipation (constipation)
  • feeling constantly tired or unwell
  • digestive difficulties
  • abdominal pain and / or swelling
  • dizziness and headache
  • itching or rash
  • hair loss or hair loss (alopecia)
  • yellowish complexion of the skin and / or the white part (sclera) Of the eyes (jaundice)

If these or other complaints occur, it is advisable to contact a doctor, who should be contacted immediately in case of jaundice.

Reporting of side effects

The appearance of undesirable effects during the use of anticoagulants can be communicated to the competent health authorities through the special report of suspected adverse reaction, also available in pharmacies.


Interactions with other drugs

When taking oral anticoagulants, you should always consult your doctor or pharmacist before taking any other medicines, including over-the-counter medicines (such as aspirin) or herbal remedies (such as St. John's wort), homeopathic medicines and supplements.

Many preparations can interact with anticoagulants, enhancing or reducing their effects, with dangerous consequences for health.

Drugs that can change the mechanism of action of oral anticoagulants include:

  • antibiotics
  • antidepressants
  • corticosteroids (used to reduce inflammation)
  • antiepileptics
  • non-steroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen (in case of fever or pain the use of paracetamol is allowed)

The detailed list of drugs to avoid can be found on the package leaflet that accompanies each medicine pack.

Interactions with food and alcohol

The use of oral anticoagulants does not require the adoption of a particular diet, as long as the diet is healthy, balanced and varied to ensure the body all the nutrients necessary for its proper functioning.

The only dietary recommendation is for people on warfarin therapy, who must keep the daily consumption of foods rich in vitamin K as constant as possible, such as leafy vegetables (such as spinach, broccoli, cauliflower and lettuce), chickpeas, liver and cranberry juice.

Vitamin k, in fact, can interfere with the action of warfarin, modifying its effects. An increase in the quantity of vitamin k introduced with the diet corresponds to a decrease in the anticoagulant effect, vice versa, a reduction in the intake of vitamin k corresponds to an increased risk of bleeding.

The doctor may change the warfarin dosage to bring the INR values ​​back to the correct range, but it is always advisable to keep the anticoagulant action in due balance through regular eating habits over time.

Alcohol also interacts with warfarin, increasing its effects. We therefore recommend moderate consumption of wine (1 glass with main meals), while the use of alcohol and spirits is strongly discouraged.

These dietary recommendations do not apply to those who use the new oral anticoagulants (NAOs). If in doubt, just ask your doctor or pharmacist.


Warfarin is not normally used during pregnancy, as it can cause bleeding of the placenta or fetus and severe birth defects in the baby. However, in some cases, it can be used in the second trimester of pregnancy if, in the doctor's judgment, the benefits of taking it outweigh the risks.

New oral anticoagulants (NAOs) are also not recommended in pregnancy, as their effects on the baby have not yet been studied.

Women who want a child must discuss this in advance with the doctor, who will evaluate whether to suspend the anticoagulant therapy or replace the oral anticoagulants with "injectable heparin. The latter, in fact, does not present risks for the baby since it does not cross the placenta and therefore, it does not reach the fetus.

Women of childbearing age undergoing oral anticoagulant therapy must use contraceptive methods other than the pill, which is contraindicated, to avoid pregnancy. In case of delays in the menstrual cycle they must promptly inform the doctor to carry out a pregnancy test.

Feeding time

Women being treated with warfarin can breastfeed safely, as there is no scientific evidence that the drug passes into breast milk.

The use of heparin is also safe during breastfeeding, while new oral anticoagulants (NAOs) are not recommended as their effects on the baby are not yet known.

In any case, before starting to breastfeed it is always good to ask your doctor or gynecologist for advice.


Anticoagulant therapy does not prevent the normal performance of daily activities, but requires the adoption of some precautions, listed below.

Surgery, invasive examinations or complex dental care

Before undergoing a scheduled surgery or invasive diagnostic test, such as gastroscopy, colonoscopy, and biopsy, you should tell your surgeon or healthcare professional what anticoagulants you are taking.

Since these drugs slow down blood clotting, there is, in fact, the risk of heavy bleeding in the event of cuts or incisions made during surgery or examination.

To avoid the risk of bleeding, in some cases it will be necessary to temporarily stop therapy.

Similarly, in anticipation of dental extractions or other invasive dental procedures, it is advisable to inform the dentist of the therapy in progress, to allow him to evaluate the risks associated with his intervention.

Depending on the case, you will have to stop the anticoagulant or take a blood sample, the day before the surgery, to make sure that the blood is clotting at the right rate.

Trauma, injuries and wounds

The use of oral anticoagulants increases the risk of bleeding in the event of trauma, injury and wounds, therefore it is necessary to avoid, or carry out with caution, all activities that can induce bleeding by adopting the following precautions:

  • brush your teeth gently, using a toothbrush with soft bristles and without putting pressure on the gums
  • use the electric razor to shave or shave, avoiding the use of traditional blades or razors
  • handle pointed or sharp objects with care, such as scissors and knives, wearing protective gloves for gardening activities
  • avoid physical or sports activities with a high risk of falls, trauma or injury, such as soccer, martial arts, and other contact sports. In any case, use suitable protective equipment, such as a helmet for cycling
  • use insect repellents, to protect yourself from inappropriate bites and stings
  • avoid intramuscular injections, if possible, as they could cause the formation of local hematomas

Identification bracelet

It is a good idea to always carry an identification bracelet or a document indicating the anticoagulant therapy you are taking (as large as a credit card that comes with the drug). This simple precaution, in emergency situations, will allow rescuers and doctors to intervene appropriately.

Please note: for the prescription of the new oral anticoagulants (NAO) a normal prescription is not sufficient but a specific therapeutic plan drawn up online by the doctor is currently required.


NHS. Anticoagulant medicines (English)

In-depth link

FEDER-A.I.P.A - Federation of Italian Associations of Anticoagulated Patients

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