Heparin is a naturally occurring anticoagulant. Heparin is contained in mast cells and is released into blood vessels at sites of tissue injury to prevent blood clots forming.

Heparin and several heparin derivatives such as enoxapain, dalteparin and tinzaparin are used to prevent patients at high risk of pulmonary embolism and deep vein thrombosis. The drug has also been used in the treatment of several other conditions and some of these are described below.

• Heparin has been tested in controlled clinical trials as a treatment for adult respiratory distress syndrome (ARDS). Suggested mechanisms include reduction in the activation and accumulation of cells in airways and neutralization of mediators and toxins from cells. Animal models have shown that heparin improves lung function.
• Heparin is being tested in controlled trials as a treatment for asthma after animal models suggested the drug could improve lung function.
• The clinical benefit of heparin in the treatment of allergic rhinitis is being tested in controlled clinical trials.
• Animal studies are being conducted to explore the effects of heparin as a treatment for allergic encephalomyelitis.
• Molecular studies suggest that heparin may have beneficial effects as an arthritis treatment, by preventing cell accumulation and collagen destruction.
• Animal models also suggest that heparin may have anticancer effects through prevention of tumor growth, angiogenesis and cancer spread.
• Controlled clinical trials have suggested potential benefits in the treatment of inflammatory bowel disease.
• In animal models, heparin prolongs survival after allografts procedures have been performed.