HEPARIN: POWERFUL AND INSTANTANEOUSLY ACTING ANTICOAGULANT

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ABOUT AUTHOR
Amitava Sinha Ray
Ranbaxy Laboratories Ltd
West Bengal, India
a.amitava.s@gmail.com

ABSTRACT
Anticoagulantis an agent that is used to prevent the formation of blood clots. Anticoagulants, such as heparin or warfarin work on chemical reactions in the body to lengthen the time it takes to form a blood clot. Heparin the anticoagulant drug that is used to prevent blood clots from forming during and after surgery and to treat various heart, lung, and circulatory disorders in human body. Heparin is comparatively a strong acid that forms water–soluble salts. It is used in treatment of venous thrombosis and its extensions, pulmonary embolism (PE), peripheral arterial embolism. Smoking and alcohol may alter response to heparin. Abrupt withdrawal of heparin may precipitate increased coagulability.

REFERENCE ID: PHARMATUTOR-ART-2267

PharmaTutor (ISSN: 2347 - 7881)

Volume 2, Issue 11

Received On: 25/08/2014; Accepted On: 31/08/2014; Published On: 01/11/2014

How to cite this article: AS Ray; Heparin: Powerful and Instantaneously acting Anticoagulant; PharmaTutor; 2014; 2(11); 30-34

INTRODUCTION
A medical student, named McLean discovered in 1916 that liver contains a powerful anticoagulant. Then Howell and Holt (1918) named it 'HEPARIN' because it was obtained from liver. However, it could be used clinically only in 1937 when sufficient degree of purification was achieved. Heparin is used as an anticoagulant drug. These are drugs used to reduce the coagulability of blood.[1]

CLASSIFICATION OF ANTICOAGULANT DRUG

Table:1 Classification of Anticoagulant Drug

In Vivo

In Vitro

Parenteral Anticoagulants

Oral

Anticoagulants

Heparin

Calcium complexing agents

Heparin, Low molecular weight heparin.

Coumarin derivatives

Indandione derivative

150 U to prevent clotting of 100 ml blood

Sodium citrate

1.65 g for 350 ml of blood, used to keep blood in the fluid state for transfusion

Heparinoids-Heparan sulfate

Bishydroxycoumarin

( dicumarol)

Phenindione.


Sodium oxalate

Danaparoid

Warfarin sod



Sodium edetate

Lepirudin

Acenocoumarol




Ancrod

Ethylbiscoumacetate




DESCRIPTION OF HEPARIN:

Fig:Chemical Structure of Heparin

Heparin is an anionic polysaccharide of mammalian origin with irregular sequence. It consists principally of alternating iduronate and glucosamine residues, most of which are sulfated.[2] It may be described as a sulfated glucosaminoglycan. Heparin has the characteristic property of delaying the clotting of freshly shed blood. It may be prepared from the lungs of oxen or the intestinal mucosa of oxen, pigs, or sheep. Heparin is often described in the literature as standard heparin or unfractionated heparin to distinguish it from low-molecular weight heparins.

Heparin is a mucopolysaccharide, having a molecular weight ranging from 6,000 to 20,000, made up of several repeating units of glucuronic acid and sulphated glucosamine. It is comparatively a strong acid that forms water–soluble salts, for instance heparin sodium.

Heparin is a natural polysaccharide that contains a large number of linear and polydisperse chains. Molecular weight of natural heparin ranges from 3.000 to 30.000 Daltons (Da), while medical grade, unfractioned heparin has an average molecular weight of 12 to 16.000 Da.

Heparin is a nonuniform mixture of straight chain mucopolysaccharides with MW 10,000 to 20,000. Heparin is present in all tissues containing mast cells; richest sources are lung, liver and intestinal mucosa.[1]

Low Molecular Weight Heparins:
Low molecular weight heparins (LMWHs) are obtained through various methods of chemical and enzymatic depolymerization from clinical-grade unfractioned heparin.

The advantages of Low molecular weight heparins are:
a) Better bioavailability.
b) Does not bind to proteins or endothelial cells.[3]
c) The entire dosage performs the anticoagulant function.
d) More predictable dose-response.
e) Dose adjustment is not needed during its administration.
f) Its plasma half-life is longer than that of unfractionated heparin.

BIOLOGICAL FUNCTION OF HEPARIN:
Heparin can regulate the activities of a wide range of proteins that are essentials to important biological processes such as ,

  1. blood clotting
  2. pathogen infection
  3. cell differentiation
  4. cell growth and migration
  5. inflammation

a) Blood clotting.
Heparin id a very potent anticoagulant. Heparin is capable of interacting with coagulation cascade proteins.

b) Pathogen infection.
Viruses and othe pathogens use the heparan sulphate chains on the wall of the target cells as receptors for a coat protein.Since exogenous heparin or its derivatives can interfere the binding by competing with the heparan sulphate the infection can be prevented.

c) Cell Differentiation, growth and migration.
Most biological functions of heparan sulphate are mediated by interactions with proteins that can be promoted or inhibited by exogenous heparin.
One of the major functions of heparan sulphate proteoglycans is the ability to regulate the activity of growth factors by different mechanism.

d) Inflammation.
The potential of heparin as an anti-inflammatory drug has been shown by modest clinical trials with patients suffering bronchial asthma, ulcerative colitis and burns.

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