Heparin: Effects, Uses & Risks

Heparin as an anticoagulant has become indispensable in today’s medicine: whether in the treatment of acute life-threatening events such as a heart attack or pulmonary embolism, or as a prophylactic administration to prevent thrombosis during surgery or long air travel, heparin and its various derivatives such as Mono-Embolex or Clexane are important basic building blocks of medical action everywhere. Yet heparin is actually a substance produced naturally in the body.

What is heparin?

It is impossible to imagine modern medicine without heparin as an anticoagulant. Heparin is a substance used in pharmacology as a drug that interferes with and inhibits blood clotting. Heparin is therefore also known as a blood thinner. Chemically, heparin is a glucosaminoglycan, i.e. a chain of amino sugars, which occurs naturally in human and animal tissue mast cells. Natural heparin is therefore originally obtained primarily from the small intestinal mucosa of pigs, which is particularly rich in this substance.

Pharmacological action

Because of the rather short-term effect of heparin, the drug is given mainly in acute emergency situations or for a short time in the hospital, and not as a permanent therapy (as is the case with other “blood thinners” such as Marcumar or aspirin). The substance can be administered into the vein (intravenously), where it takes effect immediately, or by injection into the subcutaneous fatty tissue, from where it then enters the organism slowly and continuously over a longer period of time and in lower doses. The pharmacological effect is based on an intervention in the natural clotting process of the blood: Various clotting factors swim around in our blood every day and, in response to certain stimuli, clump together with the blood platelets (thrombocytes), thereby plugging wounds, but also causing emergencies such as thromboses, strokes or heart attacks. In healthy people, this clotting activity is controlled by counterpart substances such as antithrombin III, which dissolves the constantly spontaneously coagulating clotting factors again and can thus prevent excessive blood clotting and thus infarctions and thromboses. Heparin is released by the body itself in critical situations to activate antithrombin III and increase its binding power to the clotting factors about a hundredfold. If heparin is obtained from pig intestines or bovine lungs and chemically processed, it can be administered to humans and effectively suppress their blood clotting. Many other representatives of the heparinoid group are also produced synthetically today and pharmacologically modified to make them more effective for longer or less allergenic.

Medical application and use

The range of applications for heparins is broad and spread across the spectrum of medicine: For example, injection into the subcutaneous fat tissue can be used during long airplane or bus trips to lower the risk of thrombosis. Nurses do the same in hospitals during long stays or before and after operations. Even after leg injuries, for example when a cast or splint has to be worn for a long time, it is useful to suppress blood clotting for a short time by administering a daily dose of heparin. In most cases, the original heparins are not used, but rather modified substances with the same effect but better pharmacological conditions and fewer side effects. However, classical heparin is still used: In the acute therapy of myocardial infarction, intestinal infarction, pulmonary embolism, leg vein thrombosis and stroke, heparin is administered intravenously in high doses to dissolve the existing blood clot or at least prevent it from growing any larger and thus prevent worse. However, definitive therapy, for example by cardiac catheterization, usually follows.

Risks and side effects

Heparin, because it is a substance produced naturally in the body, is in principle quite low in side effects. The main problem therefore also derives from the effect of the substance:

By inhibiting blood clotting, the risk of bleeding increases, wounds heal worse, and life-threatening internal bleeding such as cerebral hemorrhage can even occur. For this reason, freshly operated patients, people with open wounds or stomach ulcers, with severe high blood pressure or known coagulation disorders are often not allowed to receive heparin.Lower dosages or related substances such as heparinoids are sometimes a fallback option here. The administration of heparin is ultimately always a trade-off between the risk of the underlying disease and the risk of a bleeding side effect. Furthermore, allergic reactions or hair loss may occur, and osteoporosis has also been described as a side effect of long-term heparin therapy. In hospitals, the occurrence of so-called heparin-induced thrombocytopenia (HIT), i.e. a lack of blood platelets due to heparin administration, is feared. Daily monitoring of blood counts is therefore essential during high-dose heparin therapy.