When blood clots, this is normally a great advantage for our body. If we are injured, for example, clotting ensures that wounds can close and we do not bleed to death. But under certain conditions, this usually protective blood-clotting process sets in when it is not needed. Thrombosis is what physicians call such undesired clotting. The blood clots (thrombi) that form not only threaten to clog arteries and veins at the place where they form. In the worst case scenario they can break off from the vascular wall and be transported by the blood stream to other organs, where they can cause dangerous embolisms – a complete or partial plug of the blood vessel.

The best-known form of the disease is probably travel thrombosis, which can occur after sitting for long periods on long-haul flights. However, patients who are confined to bed, perhaps after surgery, are also at risk of thrombosis. For example, the large veins in the leg can be damaged when a knee or hip prosthesis is implanted. This increases the risk of what is known as venous thromboembolism: blood clots that have formed in the veins are swept into the bloodstream and become stuck in the lungs, for example. An estimated 6.5 million people worldwide die every year of the consequences of such embolisms.

Other diseases can also aggravate the risk of thrombosis: one is atrial fibrillation, a heart-rhythm disorder in which the heart does not work properly. A residual amount of blood is sometimes left behind in the heart and clots; if the thrombus is transported from there to the brain, there is risk of a stroke. Blood clots can also form in the arteries. The risk of clogging is most serious when vessels are narrowed by calcification (atherosclerosis). If the coronary vessels are affected, the result can be a heart attack or what is known as unstable angina pectoris.

The good news is that thrombosis can be prevented. People who are aware that they are at risk can take precautions. Antiembolism stockings improve the blood circulation in people who have to lie down for long periods or sit for many hours during a long-haul flight. In addition, there are drugs that can reduce the risk of undesired blood clotting.

Up to now, the most commonly used anticoagulants have had certain disadvantages, however. Some heparins cannot be taken in the form of tablets and have to be injected at regular intervals. For some patients, this is not always easy, especially when it comes to self-application. Other drugs can be taken orally (in form), but are not easy to dose because there are many interactions. The patients and their blood values have to be closely monitored. After all, the fundamental challage in preventing thrombosis is that the blood-clotting process must not be inhibited to the extent that it no longer functions if the person suffers injuries or wounds.

Bayer Schering Pharma is currently developing a novel active substance. This will be administered in tablet form once a day and is therefore easy to dose. The substance, which has proved to be very well tolerated in studies, attacks the clotting process directly by inhibiting the clotting factor Xa. This clotting factor is an important player in the complex process of blood clotting. The method offers not only a form of prevention against thrombosis – existing clots can also be treated.

The new drug is being tested in extensive clinical trials. A total of almost 50,000 patients will take part in the study program. The company is preparing the active substance for use in preventing thromboses after major orthopedic surgery, treating existing blood clots, and preventing strokes in patients with atrial fibrillation or who have already had a heart attack.

Physicians must be able to visualize blood vessels in order to diagnose existing thromboses or embolisms. The classic examination is an X-ray, with a contrast medium being injected immediately before the image is taken. Bayer Schering Pharma offers such an X-ray contrast agent.

BSP also has an innovative contrast medium which also makes it possible to visualize venous thrombi by magnetic resonance imaging (MRI). This substance has been specially designed to dock onto a blood protein, enabling it to stay in the blood vessels for longer than usual. For this reason it can be injected directly into a vein in the arm, from where it spreads throughout the vascular system. In the case of MRI, therefore, unpleasant punctures of the foot vein, which are necessary for a X-ray of the foot for example, can be avoided.

The MRI examination is primarily an aid for diagnosing and localizing a blood clot. As a result, however, it also offers a way of monitoring and controlling the effect of thrombosis therapy.

Advice for patients
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