Anticoagulant medicines reduce the blood’s natural ability to clot. Although it is important for everyone's blood to clot so that bleeding from cuts and other accidents will eventually stop, in some people it is important to slow the clotting process down with anticoagulants.
Anticoagulants, sometimes referred to as 'blood thinners', do not affect any other function of blood, such as carrying oxygen or fighting infection.
Reasons for taking anticoagulants
Anticoagulants are used to prevent and treat blood clots in people who have had a previous blood clot that has caused a health problem or those who are at risk of developing a blood clot.
Common reasons for taking anticoagulant medications:
- having a history of abnormal blood clotting, for example a clot in the leg (DVT) or on the lung (pulmonary embolism);
- having an irregular heartbeat, such as atrial fibrillation;
- having an artificial heart valve;
- following certain types of surgery (such as knee or hip replacement surgery); and
- (in some cases only) after a heart attack or stroke.
Precautions when taking anticoagulants
- Bleeding. You will bleed more easily when taking anticoagulants, even from minor bumps, scrapes or cuts. Take care when shaving or tooth brushing. Bleeding can be serious, so make sure you take your anticoagulants as directed by your doctor and pharmacist, and have regular monitoring with your doctor.
- Other medicines. Many anticoagulants are affected by medicines that are used to treat other conditions, potentially increasing your risk of bleeding or clotting. Check with your doctor before starting any new medicines, including complementary medicines.
- Surgery. If you need to have surgery, it’s important that your surgeon and doctor are aware that you are taking anticoagulation medicines. The dose and timing of your anticoagulants will most likely need to be adjusted before surgery.
- Dental procedures. Let your dentist know that you are taking anticoagulants before any dental procedures that may put you at risk of bleeding.
- Pregnancy. Some anticoagulant medicines, such as warfarin, are not suitable for use in pregnancy. If you are pregnant or planning a pregnancy, see your doctor.
- Emergency medical ID. It’s a good idea to wear or carry some medical ID that lists the medicines you are taking, and the name of your doctor. Available options include bracelets (such as MedicAlert) and other jewellery, or cards for your purse or wallet.
Types of anticoagulants
There are several different types of anticoagulants, including:
- warfarin (brand names Coumadin, Marevan);
- dalteparin (Fragmin);
- enoxaparin (Clexane);
- dabigatran (Pradaxa);
- apixaban (Eliquis);
- rivaroxaban (Xarelto); and
- fondaparinux (Arixtra).
The type of anticoagulant medicine that your doctor prescribes will depend on several factors, including:
- the reason for anticoagulation;
- other medical conditions; and
- medication side effects.
Anticoagulants can be given through a drip into a vein, by injection under the skin or as a medicine by mouth.
Sometimes, a combination of different anticoagulants is used.
Warfarin is perhaps the best-known anticoagulant medicine. For many years, warfarin (brand names Coumadin, Marevan) was the only oral anticoagulant available. It may be needed for a short time or, in many cases, for life.
People taking warfarin need regular blood tests to check the level of anticoagulation. A measure known as INR (international normalised ratio) has been developed to compare the rate of blood clotting between someone taking anticoagulants and someone who is not.
The INR of a healthy person not taking warfarin is 1.0. The longer it takes to clot, the higher the INR. For most people on anticoagulants, the INR needs to be maintained somewhere between 2.0 and 3.5.
It’s important to keep your INR in your target range:
- if your INR is below your target range, you are at risk of blood clots developing;
- if your INR is too high you are at risk of bleeding.
Factors that may affect your INR
- Vitamin K. Extra Vitamin K can counteract the effect of warfarin. Certain foods, particularly those containing high amounts of Vitamin K such as green leafy vegetables, can therefore affect your INR. It is not that you shouldn’t eat these foods, but your intake should not vary widely. Tell your doctor if you are making major changes to your regular diet. Vitamin K may also be included in multivitamins, so check this with your pharmacist.
- Alcohol can also affect your INR, so you should limit your alcohol to no more than 2 standard drinks per day and avoid binge drinking.
- Other medicines. Taking other medicines can also affect the rate of blood clotting in people taking warfarin. Warfarin has more potential for interacting with other medicines than just about any other medication, so always discuss with your doctor or pharmacist before taking any new medicines.
Several other anticoagulants have become available more recently, including:
- dabigatran (brand name Pradaxa), taken orally;
- rivaroxaban (brand name Xarelto), taken orally;
- apixaban (brand name Eliquis), taken orally; and
- fondaparinux (brand name Arixtra), which is injected under the skin.
These anticoagulants generally do not require blood test monitoring. They may be unsuitable in people with reduced kidney function.
Unfractionated heparin is an anticoagulant medicine that is given via a drip, usually in hospital. Its effect on clotting comes on and wears off quickly, and needs to be closely monitored. It is not suitable for long-term anticoagulation.
Unfractionated heparin can cause an uncommon reaction in some people resulting in a reduced number of platelets (cells in the blood involved in clotting) and problems with clotting.
Low molecular weight heparins
Low molecular weight heparins, such as dalteparin (brand name Fragmin) and enoxaparin (brand name Clexane), are more predictable than unfractionated heparin and do need to be monitored as closely.
They are given via injection under the skin, which can be self-administered at home.
Another type of medicine – antiplatelet agents – is also used to help prevent blood clots from forming. Examples include aspirin and clopidogrel (Iscover, Plavix).
Last Reviewed: 21/07/2015
1. Anticoagulants (revised February 2012). In: eTG complete. Melbourne: Therapeutic Guidelines Limited; 2015 Mar. http://online.tg.org.au/complete/ (accessed Jul 2015). 2. NHS Choices. Anticoagulant medicines (updated 4 Sep 2013). http://www.nhs.uk/conditions/Anticoagulant-medicines/Pages/Introduction.aspx (accessed Jul 2015).
Pulmonary embolism (PE) happens when a blood clot blocks one of the arteries in the lungs. Find out about the causes, diagnosis, treatment and prevention of PE.
Deep vein thrombosis
Deep vein thrombosis (DVT) occurs when a blood clot forms in the deep veins of the leg. Find out about symptoms, causes, treatment and prevention.
Video: Deep vein thrombosis
A deep vein thrombosis is the formation of a blood clot within a deep vein, usually in the legs. Numerous factors can increase the risk of a clot forming. The clot may travel to a lung and block its function, which may be life-threatening. Following some advice can help prevent this condition.
Video: Pulmonary embolism
What is a pulmonary embolism?
Pulmonary embolism occurs when a clot that has travelled from another part of the body blocks the blood supply to the lung. It commonly arises from a deep vein thrombosis (DVT).
Pulmonary embolism ultimately damages areas of the lung, causing reduced oxygen levels in the blood that can potentially lead to death. Therefore, it is a serious medical condition that needs prompt medical treatment.
What is an embolism?
Blood clotting is a normal bodily function that helps to prevent bleeding. Normally, blood clots form and then break down in a continuous process. Under certain conditions, the body cannot break them down, which can lead to potentially serious consequences.
A thrombus is a blood clot that partially blocks a blood vessel. An embolus occurs when this thrombus becomes dislodged from where it has formed and travels through the bloodstream until it becomes lodged in a narrower blood vessel.
Clots most commonly occur in the deep veins of the leg, causing deep vein thrombosis (DVT). Once a clot has formed in the deep veins of the leg, it has the potential to break off and travel through the bloodstream to another area of the body, commonly the lungs.
Pulmonary embolism is not a disease in itself, but is rather a complication from an underlying thrombosis.
Deep vein thrombosis is the most common cause of pulmonary embolism, in which a thrombus that has formed in the legs becomes dislodged and travels through the bloodstream, lodging in the lung.
How a pulmonary embolism occurs.
Less common causes of pulmonary embolism include:
- An air bubble in a vein;
- A bone fracture, which can allows fragments of bone and fat to break free into the bloodstream;
- A cancerous tumour that has broken away from a larger tumour, or;
- Amniotic fluid from pregnancy.
- Older age;
- Being inactive for long periods, especially being confined to bed due to illness;
- Having surgery, especially abdominal surgery;
- A family history of the condition;
- Being overweight;
- Having deep vein thrombosis;
- Pelvic fractures and fractures of the legs, and;
- Certain medications, such as the oral contraceptive pill.
Signs and symptoms
Pulmonary embolism may not necessarily cause any symptoms. When symptoms do occur, they may vary depending on the size, number and location of the clots and the underlying health of the persons lungs.
Some more typical signs and symptoms may include:
- Chest pain;
- Coughing up blood;
- Mild fever;
- Fast heart rate;
- Low blood pressure, and;
- Loss of consciousness.
Signs and symptoms of a deep vein thrombosis include:
- Leg pain or tenderness;
- Warm skin on the leg;
- Red or blue discolouration of the skin, and;
- Swelling in one leg.
Methods for diagnosis
Diagnosis of pulmonary embolism is based on a person's symptoms, medical history and a range of scans and tests, including:
- Ventilation-perfusion scan (V/Q) scan this test uses a very small amount of a radioactive substance to examine the lungs for a pulmonary embolism. The test involves two scans the ventilation and perfusion scans. The ventilation scan assesses the flow of air in and out of the lungs, while the perfusion scan assesses the blood flow within the lungs. A difference between the scans may be suggestive of a pulmonary embolism. The main benefit of this test is that there is no risk of radiation exposure;
- Computerised tomography (CT) scan to assess the blood vessels of the lungs. This test can accurately diagnose pulmonary embolism; however, there is the small risk of radiation exposure;
- Ultrasound of leg veins to check for the presence of deep vein thrombosis;
- Echocardiography - a useful diagnostic tool to assess the strain on the heart from pulmonary embolism, and;
- D-dimer this is a blood test that detects the by-products of a blood clot. A negative test can help rule out both deep vein thrombosis and pulmonary embolism.
Types of treatment
The main treatment for pulmonary embolism is anticoagulant therapy medication to stop further blood clots from developing. This type of medication does not break down existing clots, but it does stop an existing clot from getting bigger. The body can then eventually break down the clot.
Anticoagulant therapy is usually prescribed for several months, although some people may need to stay on it permanently. Anticoagulant therapy can be taken as an injection (known as clexane), or as oral medication such as warfarin.
In some cases, treatment may also involve thrombolytic therapy, which is the removal of the clot, usually using a type of medication. Thrombolytic medication breaks up the blood clot, but has a risk of unwanted bleeding, especially into the brain that could cause a haemorrhagic stroke. Therefore, it is generally given only when the person is seriously unwell from pulmonary embolism.
Vena cava filter
Another form of treatment may involve the insertion of a filter, via a thin tube, into a large blood vessel that returns blood from the body to the heart, referred to as the inferior vena cava. These filters stop further blood clots from reaching the lungs and are useful when anticoagulant therapy is not suitable. It is removed once there is no longer the risk of further clots.
Some more serious cases of pulmonary embolism may require surgical removal of the embolus from the lung. This is generally reserved for very large clots, or where the person is seriously unwell.
Complications from pulmonary embolism can include:
- Heart failure;
- Pulmonary hypertension where the blood pressure in your lungs and right side of the heart is too high, which means the heart has to work harder to push blood through these vessels;
- Recurrent pulmonary embolisms, and;
- Death from cardiac arrest, in which the heart stops working.
If pulmonary embolism is treated quickly, most people will make a full recovery. But when there is a large embolus, it may be life-threatening.
Given the link between deep vein thrombosis and pulmonary embolism, prevention needs to focus on ways to prevent deep vein thrombosis, including the following:
- When travelling, exercising the calf and foot muscles regularly, avoiding alcohol and drinking plenty of water to avoid dehydration;
- Maintaining a healthy weight;
- Stopping smoking;
- Getting regular exercise;
- Wearing special compression stockings, if at risk of developing deep vein thrombosis, and;
- For people having surgery or being confined to bed for long periods, being assessed for their risk of developing a deep vein thrombosis and, if necessary, taking preventative anticoagulant therapy after surgery.
TIA: transient ischaemic attack
A TIA (transient ischaemic attack), also called a mini-stroke or temporary stroke, is when there is a temporary block in the blood supply to a part of the brain.