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Taking a closer look at blood-thinning agents

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Each and every organ system, in fact each and every cell of the human body, derives its nutrition from the blood it receives.


Blood, apart from other nutrients, contains oxygen without which life cannot exist. It is basically composed of two components, the fluid (plasma) and the cellular (red, white blood cells and platelets). Normal human physiology demands that blood be in appropriate quantity and quality. Changes in either blood volume or its constituents leads to complications.


In order to maintain homeostasis the cellular (solid) and plasma (fluid) components should stay in appropriate proportions. Any alteration in this ratio leads to pathological states.


Blood must remain in fluid form and must always be in a state of motion (circulation). Sluggish blood flow, stagnation or increase in the cellular component (high viscosity) of the blood leads to clot formation which is enhanced by the presence of a rough surface over the inner lining of blood vessel. Clot (thrombus) formation within a blood vessel, whether venous or arterial, produces serious consequences.


The clinical picture depends upon the organs affected by the respective blood vessel which develops clot inside its lumen. Arterial clots are more serious than the venous ones in terms of clinical consequences.


There are intrinsic body mechanisms which prevent the clustering together of blood cells and platelets. Failure of these mechanisms (natural anti-coagulation) can lead to clot formation. In the situation of a disease, clot formation is managed by the use of anti-coagulant drugs.


Anti-coagulants commonly known as blood shining agents, constitute a crucial group of drugs used in the management and prevention of clot formation in blood vessels of various body parts, including the heart and the brain. Anti-coagulants are divided into various classes depending upon their primary pharmacological actions. They have a wide spectrum of clinical indications and usages.


Their principle action is to minimize the chances of clot formation in susceptible situations and people. They also check the detachment of clot and its embolization to distant organs once it has been formed. Anti-coagulants are widely used in various sub sets of Ischaemic Heart Disease, strokes and peripheral vascular disease.

They are particularly used on long term basis in valvular heart diseases, following valve replacement surgery with prosthetic valves and in chronic arrhythmias. Anti-coagulants are also used as short-term measure in hospitals where they are suppose to be properly monitored under a doctor's supervision.

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However, it is the long-term use of anti-coagulants (blood thinners) which needs to be discussed for the benefit of a common man. Blood thinning agents have serious side effects. They are liable to induce bleeding which can be fatal. Therefore their administration needs appropriate dosage to maintain recommended therapeutic blood levels and to avoid over or under anti-coagulation.


Under anti-coagulation undermines the purpose for which blood thinners are used and this can produce thrombo embolic events in pre-disposed situations. While in over anti-coagulation can lead to bleeding both localized as well as systemic.


Therefore once placed on a blood thinning agent, one has to follow the recommended protocol for monitoring its therapeutic efficacy and side effects. There are guidelines available for this purpose.


Warfarin sodium is most widely used for long-term anti-coagulation. This is given as once daily dose. Average daily requirement to achieve therapeutic levels ranges between three to 10 mg daily. The therapeutic activity is monitored by a simple lab test called PT (Prothrombinn Time) and an INR of 2.5 - 4 is recommended to maintain the therapeutic range. The target INR varies depending upon the under-lying condition. For example, for prosthetic valve the recommended target INR is 3.5 - 4.


It is the responsibility of the physician to educate the patient on the subject. He must explain the objective of this treatment and that for how long he wants the patient to continue taking it. He must explain the possible side effects and how to monitor those. The importance of P.T/INR values and the possible side effects in the event of abnormal values need to be stressed upon.


A number of drugs can adversely affect the pharmacological action of blood thinners. It is therefore necessary that the physician should go through the prescription and all such drugs interfering with the pharmacology of blood thinning agents be stopped. However, if their use is mandatory then the dosages of either drugs need to be adjusted accordingly.


If proper precautions are adopted, blood thinners can be taken for years, in some cases for life without any serious complications. The long-term use of blood thinners must be clearly indicated. This needs to be monitored through lab tests and regular physicians follow-up visits. This modality of treatment should not be used without due justification and in the absence of proper monitoring.

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