Substances, anticoagulating

In Vitro Anticoagulants. A number of substances have been identified that prevent coagulation of the blood when it is removed from the vascular compartment of the body. Most of these substances remove a vital constituent of the blood that is essential in the mediation of transformation of hquid blood into a soHd. 

Heparin was discovered in 1916 by a medical student at Johns Hopkins University. While attempting to extract thromboplastic substances from various tissues he discovered a substance with powerful anticoagulant activity. This was named heparin because it was first extracted from the fiver. 

Anticoagulant Any substance that inhibits, suppresses, or delays the formation of blood clots. These substances occur naturally and regulate the clotting cascade. Several anticoagulants have been identified in a variety of animal tissues and have been commercially developed for therapeutic use. 

Anticoagulants are substances that can prevent blood from clotting and, hence, are of therapeutic use in cases where a high risk of coagulation is diagnosed. They are often administered to patients with coronary heart disease and to patients who have experienced a heart attack or... 

Hirudin is a leech-derived anticoagulant that functions by directly inhibiting thrombin. A range of blood-sucking animals contain substances in their saliva that specifically inhibit some element of the blood coagulation system (Table 12.4). 

Whole blood is blood that has been aseptically withdrawn from humans. A suitable anticoagulant is added (often heparin or a citrate-dextrose-based substance), although no preservative is present. The blood is usually stored at temperatures ranging from 1-8 °C, and has a short shelf life (48 h after collection if heparin is used as the anticoagulant, or up to 35 days if citrate-phosphate-dextrose with adenine is employed). 

Medical devices may be assisted in their function by pharmacological, immunological or metabolic means, but as soon as these means are not any more ancillary with respect to the principal purpose of a product, the product becomes a medicinal product. The claims made for a product, in accordance with its method of action may, in this context, represent an important factor for its classification as MD or medicinal product. Examples of MDs incorporating a medicinal substance with ancillary action include catheters coated with heparin or an antibiotic, bone cements containing antibiotic and blood bags containing anticoagulant. ... 

In addition to these and analytical problems, users of laboratory data must also be aware of possible changes in laboratory values due to the lability of the substances in the collected specimens, the effect of anticoagulants, dietary and environmental effects, age and sex on the measured concentration. 

Coumarins are also synthesized by a variety of plant species. Medically, the most significant coumarins are dicoumarol and its derivative, warfarin. Dicoumarol was initially discovered as the active substance in mouldy sweet clover hay, which could induce haemorrhagic disease in cattle. Dicoumarol and warfarin are now used clinically as anticoagulants, as discussed in Chapter 9. 

While aspirin itself does not occur in nature, similar, less effective substances do. Willow extracts, sold in health food stores, cannot match aspirin s demonstrated effectiveness in fact, aspirin came about as an improvement on the natural salicylates. Furthermore, we may attribute aspirin s anticoagulant effect to the acetyl part of the molecule responsible for deactivating an enzyme that leads to blood-clot formation. So there is really no point in chewing on willow bark to prevent a heart attack. 

ANTICOAGULANTS. These are substances that prevent coagulation of the blood. For blood investigations made outside the body, sodium or potassium citrates, oxalates, and fluorides are sometimes used. For blood that is to be used for transfusions, sodium citrate is used. 

A structural application of 13C nmr, which shows its power in an area where H nmr is indecisive, is shown in Figure 9-48. Here, we see the high-field 13C resonances of a substance known variously as Coumadin, or the sodium salt of warfarin, 14, which is used widely as a blood anticoagulant in the treatment of diseases such as phlebitis. It also has substantial utility as a rat poison because of its anticoagulant action. 

Heparin is clearly an extraordinarily complex substance with many highly polar groups, and its mode of action as an anticoagulant is not clear. At present, because of increases in the use of artificial kidney machines, heparin is in rather short supply. 

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