Blood coagulates in the normal clotting process that keeps us from bleeding to death when we cut ourselves. But blood clots inside the blood vessels can travel to the brain, causing stroke, or to the lungs, causing a pulmonary embolus (PE), a block in the arteries of the lung. Both situations can be fatal. An abnormal heart rhythm called atrial fibrillation causes blood to pool in the heart, and pooled blood is likely to form clots. A blood clot in a leg vein, called a deep vein thrombosis (DVT), can occur when people are sedentary, such as after surgery. Anticoagulant medication is used to prevent or treat these situations by suppressing blood's normal clotting process. However, anticoagulation can cause internal bleeding and hemorrhage, so people taking these medications must have frequent tests to measure how quickly their blood clots. All anticoagulant medications have potentially dangerous side effects, require a prescription and should be taken only with regular medical supervision.
Warfarin
Warfarin is the only anticoagulant that can be given orally, and therefore the only one practical for long-term use. Warfarin can prevent clots forming in artificial heart valves and is also used to treat PEs or DVTs. It is most commonly used to prevent clots in atrial fibrillation. Warfarin's anticoagulant effects take several days to develop. Because many factors can affect its absorption, patients taking it should have regular blood tests and may require ongoing dosage adjustments.
Heparin
Heparin is a potent anticoagulant that can be injected or given intravenously (IV). Situations requiring rapid anticoagulation are treated with IV heparin because its effects begin within minutes. Heparin injections may be given to patients hospitalized after surgery to prevent them from developing DVTs. Heparin is also used in two procedures in which a patient's blood passes through a machine: open heart surgery and renal dialysis. In both cases, heparin keeps blood from coagulating in the machine. Heparin is given only in hospitals or clinics.
Enoxoparin
Enoxoparin is an anticoagulant given only by injection. Its typical use is prevention of DVTs in hospitalized patients, particularly those who have had hip or knee replacements. Enoxoparin stays active in the body much longer than heparin does, and its levels are much more predictable. This makes enoxoparin safe to give on a schedule without monitoring clotting times. Although used primarily in hospitals, enoxoparin is sometimes prescribed to outpatients for continuing treatment following a hospitalization for a PE or DVT. People taking enoxoparin at home need to learn to give themselves a subcutaneous injection, usually in abdominal fat.
Dalteparin
Dalteparin is an injected anticoagulant used short term, usually in hospitals. It is typically used to prevent DVT after hip replacement or abdominal surgery. Occasionally it is used as a short-term treatment for angina and some heart attacks. Its only long-term use is to prevent recurring DVT in some cancer patients.
Tinzaparin
Tinzaparin is used only for treatment, not prevention, of DVT and PE. It is given only by injection and used in combination with warfarin.
Bivalirudin
Bivalirudin is given as a continuous IV infusion. According to the Mayo Clinic, it is used during a hospital procedure called coronary angioplasty for patients with unstable angina. It takes effect immediately and has a very short active period in the body; one hour after stopping the infusion, coagulation returns to baseline.
Lepirudin
Lepirudin is a very expensive IV anticoagulant used to correct a condition called heparin-induced thrombocytopenia (HIT), a dangerous reaction to heparin. Patients receiving lepirudin require continuous monitoring.
Argatroban
Argatroban is another extremely expensive medication given by continuous IV. Like bivalirudin, it is used during coronary angioplasty and is also used for HIT. It requires continuous patient monitoring.
Desirudin
Desirudin is used only for clot prevention, not treatment of existing clots. It is injected twice a day following hip replacement surgery.
Fondaparinux
Fondaparinux, the synthetic anticoagulant, is used for prevention of DVT following hip surgery and hip or knee replacement. It's also used with warfarin to treat existing DVT or PE. Its effects last up to four days after last dose, and it carries a higher risk of bleeding than heparin, but it does not cause HIT.
References
- "Pharmacology for Nursing Care", Richard A. Lehne, PhD.; 2007
- The Mayo Clinic: Drugs and Supplements
- American Heart Association: Atrial Fibrillation
- American Family Physician: Outpatient Management of Anticoagulation Therapy
- American Heart Association: Treatment of Blood Clots
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