Coagulant Anticoagulant

Vitamin K: Vitamin K is fat soluble vitamin that promotes coagulation. There are three forms of Vitamin K.

Vitamin K₁ (Phylloquinone): It is obtained from plant.

Vitamin K₂ (Menaquinone): It is synthesised in intestine

Vitamin K₃ : It is synthetic analogue.

Vitamin K is used by body to synthesize coagulation factors II, VII, IX, & X in liver.  Vitamin K deficiency does not occur due to dietary deficiency. It becomes ineffective during liver disease because it is utilized only by liver to synthesize coagulation factors.

Uses: It is used to treat haemorrhage. But its action starts after 24 hours. Fresh frozen plasma is used to control immediate bleeding. (Haemorrhage) 

                        

                                                           Anticoagulants

 There are two types of anticoagulants:

1 Heparin

2.  Vitamin K Antagonist

            Warferin sodium, acenocoumarol, Dicoumarol

            Anisindione, Phenindione, Diphenadine

            Hirulog, Hirudin

Heparin: Heparin is polysaccharide. It consists of long chain of sulphated disaccharide units. It contains sulphate and carboxylic acid group that make it highly acidic. Heparin is found as heparin-histamin complex in mast cell secretary granules. It is rapid acting anticoagulant that produce effect within a minute. It is administered intravenously. It mainly interfere in formation of thrombin.

Mechanism of Action: Body has antithrombin-III that converts active clotting factors IIa (Prothrombin), IXa (Christmas factor), Xa (Stuart power factir), XIa (Plasma thromboplastin Antecedent), XIIa (Hageman factor) to inactive form. This inactivation is slow process. Heparin potentiates aantithrombin III action to inactivate thrombin and other coagulation factors. Antithrombin III is also known as heparin cofactor.

Binding of heparin with thrombin depends upon chain length of heparin. Increase in chain length of heparin increases binding affinity of heparin with thrombin. Thus high molecular weight heparin has more affinity to thrombin and low molecular weight has low affinity with thrombin. But low molecular weight heparin has high affinity to coagulation factor Xa. Thus low molecular weight heparin is also used as anticoagulant. Ex of low molecular weight heparin: Dalteprin, Enoxaprin, Tinzaprin.

Chronic use of heparin decreases antithrombin III activity. This may increase chance of thrombosis. Low dose of heparin is recommended in chronic administration of heparin. It minimise risk of thrombosis.

Pharmacokinetics: It is not absorbed orally and destroyed by gastric juic in stomach. Thus it is administered by intravenous or subcutaneous route. It does not cross placental barriet. It is metabolised in liver.

Therapeutic Uses:

·         It is antithrombic drug to treat deep vein thrombosis. And embolism.

·         It is used as prophylactic agent to prevent post operative thrombosis

·         It prevent thrombosis in myocardial infarction

·         It is used during dialysis to prevent thrombosis

·         It does not cross placental barrier thus it is drug of choice in venous thrombosis and embolism in pregnant women.

Adverse Effects: Increase in bleeding time, hypersensitivity reaction and thrombocytopenia (Low blood platelet count). 

Pharmacokinetics: Coumarin anticoagulants are administered by oral, IM or rectal route. Food in GIT interferes with absorption of Coumarin anticoagulants. However they are completely absorbed from GIT upon oral administration. Warfarin has high affinity with with plasma proteins i.e about 95% to 99%. This affinity restricts its distribution to CSF, and breast milk. But it is well distributed and readily crosses placental barrier.

Several drugs have high affinity with plasma proteins than warferin. These drugs displace warferin from plasma protein. Free warferin will circulate in body and it will potentiate action of warferin.

Antocoagulant effects vary from person to person. Thus its dose must be adjusted carefully.

Adverse Effects:

·         Main side effect is haemorrhage. It can be treated by oral administration of vitamin K. In severe condition vitamin K is administered by IV route.

·         Warferin produces teratogenic effect because it can cross placental barrier. In first trimester it produces facial and CNS abnormalities.In second and third trimester it produces hypoprothrombinemia.

Precaution: It should be administered with caution in patients suffering from bleeding disorder, peptic ulcer, severe wounds etc.

Uses: They are used as anticoagulant in pulmonary embolism, deep vein thrombosis, Thromboembolism.

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