It is a complex of sulfates of heparin, dermatan and chondroitin. It acts through antithrombin III. It is anti-factor Xa and to a lesser extent it is also inhibitor of thrombin.
Extraction:
It is obtained from porcine mucosa.
Administration and elimination:
It is administered subcutaneously and is eliminated through kidneys.
Therapeutic uses:
Prophylactically, it is used in deep vein thrombosis in hip replacement surgery.
It is effective in Type-II, heparin induced thrombocytopenia.
Adverse effects:
Allergic reactions such as anaphylaxis or asthma may develop. Hemorrhage may occur.
Excess danaparoid can be displaced by plasmapheresis.
Saturday, April 2, 2011
Lepirudin
It is a polypeptide and highly specific direct thrombin antagonist whereas it shows no effect on antithrombin-III.
Production:
It is synthesized by recombinant DNA technology in yeast cells.
Mechanism of action:
One molecule of lepirudin gets bind to one molecule of thrombin causing stoppage of thrombogenic effect of thrombin.
Administration:
It is administered intravenously.
Pharmacokinetics:
It undergoes hydrolysis in the body. Its half life is 1 hour. Drug and its metabolites are excreted in the urine.
Therapeutic uses:
It is used effectively in the treatment of thrombocytopenia induced by heparin.
It is also used for other thromboembolic disorders and also causes stoppage of further thromboembolic complications.
Adverse effects:
It may cause bleeding. The drug forms complex with antibody in the body and anticoagulant effect may be elevated, than required, by the slower rate of excretion of the drug-antibody complex from the body.
It may also cause certain allergic reactions of the skin and air passages.
Production:
It is synthesized by recombinant DNA technology in yeast cells.
Mechanism of action:
One molecule of lepirudin gets bind to one molecule of thrombin causing stoppage of thrombogenic effect of thrombin.
Administration:
It is administered intravenously.
Pharmacokinetics:
It undergoes hydrolysis in the body. Its half life is 1 hour. Drug and its metabolites are excreted in the urine.
Therapeutic uses:
It is used effectively in the treatment of thrombocytopenia induced by heparin.
It is also used for other thromboembolic disorders and also causes stoppage of further thromboembolic complications.
Adverse effects:
It may cause bleeding. The drug forms complex with antibody in the body and anticoagulant effect may be elevated, than required, by the slower rate of excretion of the drug-antibody complex from the body.
It may also cause certain allergic reactions of the skin and air passages.
Heparin
Introduction:
Presence in the body:
It is present in the body in the form of histamine-macromolecule complex in the mast cells. (Its functional role in the body is not much clear.)
Extraction of heparin:
It is obtained on commercial scale from
1. Porcine intestine
2. Bovine lung
Properties of heparin:
1. Unfractionated heparin is a mixture of straight chain anionic glycosaminoglycans with wide range of molecular weight.
2. Due to the presence of sulfate group and carboxylic acid groups it is strongly acidic.
Enoxaparin is a low molecular weight (LMWH) heparin. LMWH are prepared by either chemical or enzymatic depolymerization of unfractionated heparin.
Mechanism of action:
It causes a decreased formation of fibrin by changing the activity of plasma protease inhibitor antithrombin III.
Therapeutic Uses:
Heparin is used mostly in postoperative venous thrombosis and various other thrombotic diseases such as pulmonary embolism and myocardial infarction.
It is also used in extracorporeal devices such as dialysis machine to prevent thrombosis.
Note: Heparin and enoxaparin are drugs of choice in venous thromboembolism in pregnancy as they do not cross placenta.
Administration:
Heparin is administered IV or deep subcutaneously. And enoxaparin is administered subcutaneously.
Pharmacokinetics:
Heparin has rapid onset of action and this action is finished rapidly after the stoppage of treatment with heparin.
Anticoagulant effect of heparin takes place within minutes after IV injection and 1-2 hours after subcutaneous injection. Anticoagulant effect of LMWH takes about 4 hours to take place after subcutaneous injection.
When heparin gets bind to plasma proteins the activity is neutralized.
Although heparin remains in the general circulation but when taken up by monocyte or macrophage system, it undergoes depolymerization and desulfation leading to inactive products.
The drug and its metabolites are excreted through urine.
Half life of LMWH is approximately 4 hours which is nearly double than that of larger species. Renal insufficiency may prolong its half life.
Dosage:
It is given prophylactically in the dose of 5000 units subcutaneously, two or three times in a day.
For diseases which have already been developed, initially 5000-10,000 units will be given intravenously followed by continuous infusion of 900 units per hour.
Adverse effects:
Enoxaparin causes less thromboembolic problems than heparin.
Some of the adverse effects common to them are:
1. Hemorrhage
2. Hypersensitivity reactions such as fever, chills, urticaria and anaphylactic shock.
3. Chronic administration can decrease antithrombin III activity leading to thrombosis.
4. Transient alopecia can also occur.
5. Heparin induced thrombocytopenia (platelet count can decrease up to 50%), which is of two types:
Type-I: which is mild and is for 1st 5 days
Type-II: Which is IgG mediated and is very serious and is with in 5-14 days
Antidote:
Protamine sulfate
Presence in the body:
It is present in the body in the form of histamine-macromolecule complex in the mast cells. (Its functional role in the body is not much clear.)
Extraction of heparin:
It is obtained on commercial scale from
1. Porcine intestine
2. Bovine lung
Properties of heparin:
1. Unfractionated heparin is a mixture of straight chain anionic glycosaminoglycans with wide range of molecular weight.
2. Due to the presence of sulfate group and carboxylic acid groups it is strongly acidic.
Enoxaparin is a low molecular weight (LMWH) heparin. LMWH are prepared by either chemical or enzymatic depolymerization of unfractionated heparin.
Mechanism of action:
It causes a decreased formation of fibrin by changing the activity of plasma protease inhibitor antithrombin III.
Where as enoxaparin binds to anti-thrombin and affects more on Factor Xa as compared to thrombin (Factor IIa).
Therapeutic Uses:
Heparin is used mostly in postoperative venous thrombosis and various other thrombotic diseases such as pulmonary embolism and myocardial infarction.
It is also used in extracorporeal devices such as dialysis machine to prevent thrombosis.
Note: Heparin and enoxaparin are drugs of choice in venous thromboembolism in pregnancy as they do not cross placenta.
Administration:
Heparin is administered IV or deep subcutaneously. And enoxaparin is administered subcutaneously.
Pharmacokinetics:
Heparin has rapid onset of action and this action is finished rapidly after the stoppage of treatment with heparin.
Anticoagulant effect of heparin takes place within minutes after IV injection and 1-2 hours after subcutaneous injection. Anticoagulant effect of LMWH takes about 4 hours to take place after subcutaneous injection.
When heparin gets bind to plasma proteins the activity is neutralized.
Although heparin remains in the general circulation but when taken up by monocyte or macrophage system, it undergoes depolymerization and desulfation leading to inactive products.
The drug and its metabolites are excreted through urine.
Half life of LMWH is approximately 4 hours which is nearly double than that of larger species. Renal insufficiency may prolong its half life.
Dosage:
It is given prophylactically in the dose of 5000 units subcutaneously, two or three times in a day.
For diseases which have already been developed, initially 5000-10,000 units will be given intravenously followed by continuous infusion of 900 units per hour.
Adverse effects:
Enoxaparin causes less thromboembolic problems than heparin.
Some of the adverse effects common to them are:
1. Hemorrhage
2. Hypersensitivity reactions such as fever, chills, urticaria and anaphylactic shock.
3. Chronic administration can decrease antithrombin III activity leading to thrombosis.
4. Transient alopecia can also occur.
5. Heparin induced thrombocytopenia (platelet count can decrease up to 50%), which is of two types:
Type-I: which is mild and is for 1st 5 days
Type-II: Which is IgG mediated and is very serious and is with in 5-14 days
Antidote:
Protamine sulfate
Classification of anti-coagulants
These drugs prevent the clotting of the blood.
Oral Anti-coagulants:
Warfarin Na, Phenprocoumon, Dicumarol (Bishydroxycoumarin), Diphenadione, Phenindione, Acenocoumarol, Coumetarol
Thrombin inhibitors:
Heparin, Hirudin, Enoxaparin, Hirugen, Lepirudin, Danaparoid
Fibrinolytic (Thrombolytic) drugs:
Streptokinase (Plasminokinase), Anistreplase, Urokinase, Tissue plasminogen activator, Staphylokinase
Anti-thrombotic drugs:
Aspirin, Dipyridamole, Ticlopidine, Sulfinpyrazone, Clopidogrel, Abciximab, Eptifibatide, Tirofiban
Extra-vascular anti-coagulants:
Fluorides, Citrates, Oxalates
Oral Anti-coagulants:
Warfarin Na, Phenprocoumon, Dicumarol (Bishydroxycoumarin), Diphenadione, Phenindione, Acenocoumarol, Coumetarol
Thrombin inhibitors:
Heparin, Hirudin, Enoxaparin, Hirugen, Lepirudin, Danaparoid
Fibrinolytic (Thrombolytic) drugs:
Streptokinase (Plasminokinase), Anistreplase, Urokinase, Tissue plasminogen activator, Staphylokinase
Anti-thrombotic drugs:
Aspirin, Dipyridamole, Ticlopidine, Sulfinpyrazone, Clopidogrel, Abciximab, Eptifibatide, Tirofiban
Extra-vascular anti-coagulants:
Fluorides, Citrates, Oxalates
Natural anti-coagulants present in the body
These are of the following types:
1. Those that causes inhibition of fibrin (Fibrin Inhibitors)
These are basically inhibitors of protease. They causes the inhibition of coagulation proteins as they move from the site of vessel injury.
2. Those that causes lysis of fibrin (Fibrinolytics)
These are basically tissue plasminogen activators.
1. Those that causes inhibition of fibrin (Fibrin Inhibitors)
These are basically inhibitors of protease. They causes the inhibition of coagulation proteins as they move from the site of vessel injury.
2. Those that causes lysis of fibrin (Fibrinolytics)
These are basically tissue plasminogen activators.
Hemostasis
It refers to the spontaneous arrest of the flow of blood from a vessel which is damaged.
Hemostatic response:
Vasospasm:
Vessels become spasmodic suddenly after the vessel is damaged.
Formation of platelet plug:
After the endothelium is damaged the platelets get stick to collagen as well as to each other resulting in the formation of platelet plug.
Several factors are released by platelets such as ADP, TXA2, and serotonin which results in further aggregation of platelets as well as vasoconstriction.
Next in the process, aggregated plug of platelets make it possible for the platelet factor 3 availability leading to the sequence of coagulation process further to take place.
Fibrin reinforcement of platelet plug:
A series of reactions are activated after the stimulation of coagulation system. Coagulation system works through two interrelated processes – Intrinsic and extrinsic processes.
Extrinsic pathway:
Extrinsic denotes something that comes from outside. Extrinsic pathway denotes a series of reactions which is activated by tissue factor that comes from outside of blood.
It activates Factor VII by a tissue factor i.e. thromboplastin
Intrinsic Pathway:
Intrinsic denotes something which is found in body part. In the intrinsic pathway proteins for the activation of the process of blood coagulation are present in the blood.
Intrinsic process activates Factor XII.
Both of these processes mainly activate the formation of thrombin.
And in the final result fibrin molecules are released which are helpful for giving firmness to the platelet plug.
Hemostatic response:
Vasospasm:
Vessels become spasmodic suddenly after the vessel is damaged.
Formation of platelet plug:
After the endothelium is damaged the platelets get stick to collagen as well as to each other resulting in the formation of platelet plug.
Several factors are released by platelets such as ADP, TXA2, and serotonin which results in further aggregation of platelets as well as vasoconstriction.
Next in the process, aggregated plug of platelets make it possible for the platelet factor 3 availability leading to the sequence of coagulation process further to take place.
Fibrin reinforcement of platelet plug:
A series of reactions are activated after the stimulation of coagulation system. Coagulation system works through two interrelated processes – Intrinsic and extrinsic processes.
Extrinsic pathway:
Extrinsic denotes something that comes from outside. Extrinsic pathway denotes a series of reactions which is activated by tissue factor that comes from outside of blood.
It activates Factor VII by a tissue factor i.e. thromboplastin
Intrinsic Pathway:
Intrinsic denotes something which is found in body part. In the intrinsic pathway proteins for the activation of the process of blood coagulation are present in the blood.
Intrinsic process activates Factor XII.
Both of these processes mainly activate the formation of thrombin.
And in the final result fibrin molecules are released which are helpful for giving firmness to the platelet plug.
Thursday, March 31, 2011
Imipramine
It is an anti-arrhythmic drug and belongs to class IA of drugs.
Action:
It inhibits the reuptake of serotonin and norepinephrine.
Uses:
It is an anti-arrhythmic drugs and is also used in depression and enuresis in children aged 6 years.
Action:
It inhibits the reuptake of serotonin and norepinephrine.
Uses:
It is an anti-arrhythmic drugs and is also used in depression and enuresis in children aged 6 years.
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