Blood Clot Medicines

Anticoagulant (anti-clotting) medicines
These reduce the ability of your blood to clot. They prevent clots from forming and stop existing clots from getting bigger and are therefore used in the prevention and/or treatment of VTE. They include:

• Unfractionated heparin (UFH) and low molecular weight heparins (LMWHs) – Heparin is a protein that interferes with clotting by reducing the production of blood-clotting proteins. LMWHs are small fragments of heparin that are longer lasting than UFH and examples include enoxaparin and dalteparin.
  
  These drugs are used in both the prevention and treatment of VTE. They have a rapid anti-clotting effect but must be given by injection and are therefore less convenient than the oral medicines.
  
  
• Vitamin K antagonists (VKAs) – These prevent the blood from clotting through their effects on vitamin K, a factor that is important in activating the clotting process. Warfarin is a well-known example of this group of anticoagulants that has been used successfully for the last 50 years in the prevention of thrombosis. It is an oral anticoagulant that is taken as a tablet.
  
  If you are given warfarin, you will need to have regular blood tests and sometimes the dose may need to be adjusted to ensure you are taking the most suitable dose for you. There are many foods and medicines that warfarin cannot be taken with and so it is not suitable for everyone. Your doctor will therefore check through any other medicines you may be taking and tell you which foods you should avoid whilst taking warfarin.
  
  
• Direct thrombin inhibitors (DTIs) – Thrombin is a protein found naturally in the blood that promotes clotting. DTIs attach directly to thrombin, to stop it from working. As a result, thrombin is no longer able to form an unwanted blood clot.

DTIs are effective in treating venous thromboembolism (VTE) and in preventing the occurrence of VTE following orthopaedic surgery. They are a group of newer anticoagulant medicines that include ximelagatran, the first oral (by mouth) treatment of its kind. Ximelagatran is in tablet form and can be taken with or without food and together with most other drugs. It acts quickly and does not require your blood-clotting ability to be monitored.

Other anti-clotting medicines

• Antiplatelet medicines – Platelets are cells present in the blood that are involved in the formation of blood clots. Antiplatelet medicines reduce the ability of blood platelets to stick together. Aspirin is the most common antiplatelet drug but it is less effective than the anti-clotting drugs that are normally used in the management of deep vein thrombosis (DVT) or pulmonary embolism (PE). However, in high-risk patients who cannot tolerate normal anti-clotting treatment, aspirin is occasionally used.
  

Side effects of anticoagulants
Anticoagulants and other medicines that affect the clotting of blood increase the risk of bruising and bleeding (such as nose bleeds). They also make the blood take longer to clot after a cut. As your body’s ability to stop bleeding is reduced, you should try to avoid activities that may cause a serious injury and inform your doctor if you notice any of the following signs whilst taking such medicines:

• blood in your urine
• red or black stools
• coughing up or vomiting blood or material that looks like ground coffee
• monthly periods that are clearly heavier or longer than normal