Heparin anticoagulant activities

Table L Intensity of Labelling versus Heparin Anticoagulant Activity...

Before administering the first dose of heparin, the nurse obtains the patients vital signs. The most commonly used test to monitor heparin is activated partial thromboplastin time (APTT). Blood is drawn for laboratory studies before giving the first dose of heparin to obtain baseline data (See the discussion on preadministration assessment for the oral anticoagulants.)... 

The relationship between structure and anticoagulant activity of heparin was a conundrum that puzzled Stacey. He did not solve the problem, but demonstrated that certain structural features of heparin (for example, extensive release of amino groups) alone were not responsible for the biological activity. 

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. 

FIGURE 7.2 LMWH inhibits factor Xa and minimally affects factor Ha thus, activated partial thromboplastin time is not used to measure its anticoagulant activity. (Reprinted from the American Family Physician published by the American Academy of Family Physicians, February 15th, 1999, in an article entitled Low-molecular-weight heparin in outpatient treatment of DVT. )... 

The final yield and purity of a heparin preparation depend largely on the use of appropriate, analytical methods at different stages of extraction and purification. Heparin in tissue extracts is still most commonly determined biologically, by such assays as the U.S.P. assay for anticoagulant activity. It is now recognized10 that the anticoagulant activity does not measure the actual concentration of heparin (see also Sections XII and XIII). 

It is of interest to note that the crystalline barium heparinate, which is an acid salt, tends to lose its anticoagulant powers very readily and that the authors consider that sulfur content gives no indication of heparin activity.93 Some polysaccharide sulfuric esters from marine algae possess anticoagulant activity. 

The answer is d. (Hardman, p 1346.) A slow intravenous infusion of protamine sulfate will quickly reverse the bleeding. Protamine binds to heparin to form a stable complex with no anticoagulant activity It may also have its own anticoagulant effect by binding with platelets and fibrinogen. 

When warfarin and dicoumaroi are given to a patient, 2-3 days are required to see their full anticoagulant activity. Heparin is oftOT given to provide short-term antico ulant activity. 

The physiological function of heparin is not completely understood. It is found only in trace amounts in normal circulating blood. It exerts an antihpemic effect by releasing lipoprotein lipase from endothehal cells heparinlike proteoglycans produced by endothelial cells have anticoagulant activity. Heparin decreases platelet and inflammatory cell adhesiveness to endothelial cells, reduces the release of platelet-derived growth factor, inhibits tumor cell metastasis, and exerts an antiproliferative effect on several types of smooth muscle. 

Tincture of the dried seed, on agar plate at a concentration of 30 p,L/disc, was inactive on Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus. Extract of 10 g plant material in 100 mL ethanol was used b Anticoagulation activity. Serpin BSZx (an inhibitor of trypsin and chemotrypsin) inhibited thrombin, plasma kallikrein, factor Vlla/tissue factor, and factor Xa at heparin-independent association rates. Only factor Xa turned a significant fraction of BSZx over as substrate. Activated protein C and leukocyte elastase were slowly inhibited by BSZx, whereas factor Xlla, urokinase and tissue type plasminogen activator, plasmin and pancreas kallikrein, and elastase were not or only weakly affected. Trypsin from Fusarium was not inhibited, while interaction with subtilisin Carlsberg and Novo was rapid, but most BSZx was cleaved as a substrate L... 

Mechanism of Action A protein that complexes with heparin to form a stable salt. Therapeutic Effect Reduces anticoagulant activity of heparin. 

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