drugs in haematological disorders

1

COAGULANT AND ANTICOAGULANTS

Prepared by:

Prof. Mirza Anwar BaigAnjuman I Islam's Kalsekar Technical Campus,School of

Pharmacy.New Panvel,Navi Mumbai

2

Topic Learning outcomes

1.Classification of drugs

2.Detail pharmacology

a)Mechanism of action

b)Therapeutic uses

c)Adverse effects

2

Classification of Coagulants1. Agents acting locally eg: Thrombin2. Transfusional agentsa.Human fibrinognb.Anti haemophilic globulinc.Plasma or blood3. Non transfusional agentsa.Vitamin Kb.Epsilon Amino Caproic Acid (EACA)c.Tranexamic Acidd.Ethamsylatee.Aprotininf.Desmopressin

3

4

1. Agents acting locally

a. Thrombin

Source: bovine/human plasma Properties: Stable as dry powder, stored between 2 to

8 C. Inactive below pH 5.Uses: Restricted to local application in oozing of blood.

b. Thromboplastin:Source: Prepared from acetone extracts of brain/lung tissue of killed rabbits.Use: To dertermine prothombin time.

As a local haemostatic in surgery.

4

5

c. Fibrin:Source: obtained from human plasmaUses: 1.It is used in dehydrated form as sheet to cover bleeding surface.2.Used in combination with thrombin to hold it over bleeding area.

d.Gel foam :It is porous, pressed form of gelatin spongeUses: Used in conjunction with thrombin to control oozing of blood.Completely absorbed may be left in place after suturing of wounds.Available as cones,packs, sponges and powders.

5

6

e. Oxidized cellulose:1.It is surgical gauze treated with nitrogen dioxide.2.It promote clotting by a reaction between haemoglobulin and cellulosic acid.3.It becomes sticky when mixed with tissue juice and exert its haemostatic action.4.Absorbed within 2 to 10 days interfere with bone regeneration.

f. Microfibrillar collagen:Source: Prepared from bovine collagen.Use: When applied to bleeding surface, attracts platelets to form plug followed by natural clot.Used in capillary bleeding.It is non allergic but can promote local infection and abscess

formation.It is inactivated by autoclaving and hence should not be

sterilized.

6

7

2. Transfusional agents:a)Human fibrinognb)Anti haemophilic globulinc)Plasma or blood

8

a. Human fibrinogen:

Source: Human plasmaUses: 1.It is used for restoring normal fibrinogen levels in haemorrhagic complications caused by acute afibrinogenemia.2.Fibrinogen and thrombin may be employed together for local haemostasis.

b. Antihaemophilic globulin (AHG)1.Haemophilia A and B (Christmas disease) are two commonest hereditary haemorrhagic states. Due to deficiency of specific clotting factor VIII and IX respectively.

2.Antihemophilic globulin or concentrate factor VIII is highly effective in treatment of hemophilia A.

3.It is now prepared by DNA recombinant technique.

4.Half life is 12 hours.

5.Desmopressin increases AHG blood level by increasing its release.

8

9

6. Are very expensive and may be associated with greater risk of inducing IgG antibodies to factor VIII.

7. Probably act locally at the site of tissue injury.

8. Treatment should be guided by the physician experienced in the case of hemophilia.

9.Christmas disease: fresh or stored plasma infusion is indicated to replenish the factor IX which is stable on storage.

c. Plasma or Blood

i. Fresh frozen plasma is used in coagulation disorders as it

provides all clotting factors.

ii.Concentrated of factor VIII or preparation containing factors

II,VII,IX,X are also available for specific deficiencies.

iii.Whole blood transfusion is not preferable as it carries risk of

transfusion reactions.

9

10

3. Non/ Transfusional agents:a)Vitamin Kb)Epsilon Amino Caproic Acid (EACA)c)Tranexamic Acidd)Ethamsylatee)Aprotininf)Desmopressin

11

a. Vitamin K:

1.It comprises of 3 distinct fat soluable, naphthoquinone compounds2.Participate in biosynthesis of several clotting factors.3. Vitamin K1 is found in several foods. fat- soluable,Phytonadione (Phylloquinone)4. Vitamin K2 is produced by bacteria in the GI T.5. Vitamin K3 is synthetic compound.

Fat soluable: Menadione,Acetomenaphtone Water soluable: Mendione sod.bisulfite. Menadione sod.Diphosphate.

Pharmacological actions:i.Participate in carboxylation of the glutamic acid residues of prothrombin and factors VII,IX,X in the final stage of synthesis.ii.Also involve in electron transport (Coenzyme) and oxidative phosphorylation.

11

12

Absorption, fate and excretion:a)Produced by the flora of human intestine.b)Fat soluable vitamin K1 and K2 are absorbed in presence of bile salts while water soluable K3 (Menadione) absorbed even in their absence.

Adverse reactions:a)Rare after oral adminstration.b)Serious anaphylactoid reactions after IV use.c)Large doses of synthetic menadione produce haemolytic anemia, hyper-bilirubinemia, kernicterus in new born.d)Menadione competes with bile salts for glucuronide detoxification causing accumulation of bile salts in blood result in Juandice.

12

13

Therapeutic uses:

1. Adult vitamin K deficiency: produced by a. Malabsorptionb. Obstructive juandicec. Prolonged malnutrition.

Menadione used2. Vitamin K deficiency in infants: during acute diarrhoea.3. Neonatal vitamin K deficiency:4. Bleeding state during oral anticoagulant therapy

Vitamin K generally given orally but require bile salt for absorption.Menadione preparation are NOT used. May cause adverse reactions in neonates with vitamin K deficiency. Should be avoided in pregnancy to avoid haemorrhagic disease.

13

14

b. Epsilon amino caproic acid

1.Water soluble analogue of lysine.

2. Mechanism of action:

Inhibits plasminogen activation.

a)It is reversibly occupying lysine

binding Site on plasminogen.

b)Activation of plasminogen to plasmin

is Inhibited.

c)Result in inhibition of fibrin binding to

Plasminogen.

Hence inhibit fibrinolysis and stabilize the clot.

14

15

ADME:

15

1.Orally absorbed

2.60 to 90% excreted in urine.

3.A blood level of 13mg/100 ml of blood required for plasminogen inhibition.

4.130 mg/100 ml of blood required for inhibition of plasmin activity.

ADVERSE EFFECTS:

Nasal stiffness, abdominal discomfort, dyspepsia, hypotension, skin rashes etc.

16

Therapeutic uses:

16

Used in prevention of hyper plasminaemic bleeding state due to damage of tissues rich in plasminogen activator.For examplea.Primary menorrhagiab.During prostatic surgery: contraindicated in hematuria (risk of ureteral occlusion by un lysed clot)c.Upper GI bleedingd.Bleeding after dental extraction.e.Bleeding associated with thrombocytopenia, postpartum hemorrhage.

17

c. Tranexamic acid (TA):

17

Derivative of lysine,10 time more potent & longer duration of action than EACA .Indications are similar to EACA.Adverse effects are mild inlcude nausea,diarrhoea hypotension.

Both EACA and TA are contraindicated in patients with subarachnoid bleeding because they may induce vasospasm and ischemic stroke.

d. ETHAMSYLATE:

1. Used for similier indication as EACA and TA.2. Probably act by correcting abnormal platelet aggregation ,does not stabilize fibrin.

18

e. Aprotinin:

18

It is polypeptide obtained from bovine lungs.Mechanism of action:1. It inhibits the action of several proteases like plasmin,trypsin, chymotrypsin, kallikrein by forming reversible enzyme-inhibitor complex.2. By binding to plasmin, aprotinin prevents the degradation of fibrin and fibrinogen (COAGULANT EFFECT).3. Prevent plasmin-induced degradation of platelet glycoprotein 1b, hence preserve platelet activity (COAGULANT EFFECT). 4. In addition, at higher doses aprotinin also inhibits tissue and plasma kallikrein HENCE inhibits activation of Factor XII (responsible for synthesis of thrombin), would decrease the amount of thrombin (Powerful platelet aggregator) generated, (WEAK ANTICOAGULANT EFFECT)5. Hence inhibit initiation of both coagulation and fibrinolysis.6. Was used in cardiac surgery to reduce blood loss.

Withdrawn from MarketBecause of cardiovascular toxicity,stroke and renal toxicity.

19

f. Desmopressin:

19

Analogue of arginine Vasopressin. (antidiuretic,vasocontrictor,analgesic)Increases for short time plasma concentration of factor VIII in hemophiliacs and von willebrand factor (required for platelet adhesion) in von Willebrand disease. (Treatment of choice)Therapeutic uses:It shortens or normalize bleeding time in patients with congenital defects of platelets.Acquired bleeding during uremia or use of aspirin.Acute variceal bleeding.

20

g.Conjugated estrogen:

20

1.It improves platelets functions,shorten the prolonged bleeding time.2.Compared to desmpressin it has a delayed onset but much longer duration of action.3.Can be combined with desmopressin for synergestic effect.

h. Vitamin C:Specifically control bleeding due to scruvey.

i. Snake venome: (copper head and russel viper)

Enhances coagulation by stimulating thrombokinase.

21

ANTICOAGULANTS

21

CLASSIFICATION1. Used in invivo A. Parenteral anticoagulants (Fast acting): Eg; Heparin,Bivalirudin,Dabigatran, Heparinoids B. Oral anticoagulants (Slow acting) i. Coumarin derivatives eg. Bishydroxycoumarin etc ii. Indandione derivative eg. Phenindione2. Used in invitro

A. HeparinB. Calcium complexing agent eg. Sodium citrate

22

A. Parenteral anticoagulants (Fast acting): Heparin

22

1. Heparin was discovered in 1916 by Mclean, a medical student.

2. It is naturally occurring anticoagulant, mole.wt is 5000-3000 daltons.

3. Found in granules of mast cells, abundant in liver and in lungs.

4. Commercial heparin is obtained from lungs and intestinal mucosa of pigs and cattle.

5. It composed of mucopolysaccharides composed of number of sulfated D-glucosamine and D-glucuronic acid linked together through oxygen bridge.

6. The high content of esterifies sulfuric acid makes heparin strongly electronegative compound.

7. Anticoagulant activity is attributed to its strong electronegative charge.

23

Pharmacology of heparin:

23

1. Blood coagulation:

i.Prevent clotting of blood in vitro and invivo.

ii.Act on all the three stages of coagulation.

iii.It activates antithrombin III which then inactivate

IXa and Xa & thrombin.

iv.AT-Heparin complex is 1000 time

active inhibitor than AT alone.

v. The binding of heparin with AT

Changes the confirmation of AT

vi. Thus AT-Heparin complex easily

Bind to serine protease of Xa.

(atleast 5 saccharide of heparin are

essential)

2424

vii.Attachment of heparin antithrombin complex to thrombin requires at least 18 saccharide units.viii.Formation of fibrin thus prevented.ix.Small dose of heparin have much less antithrombin activity but inhibit factor Xa (a critical moiety of coagulation).x. Small dose is used s.c for prophylaxis.xi.Prolong clotting time 2 to 2.5 times.2.Effect of lipoprotein lipase:Activate the lipoprotein lipase and abolishes the cloudiness of the hyper lipemic plasma (Tyndall effect).3.Antiplatelet:Inhibit platelet aggregation and prolong the bleeding time.4.Miscellaneous actions:Inhibits aldosterone secretion and causes hyperkalemia.Have some antiinflammatory actions.

25

ADME:

25

1.Poorly absorbed orally.2.Well absorbed after SC injection.3.When given exogenously taken up by mast cell and act like a storage depot.4.Metabolized by liver by heparinase.5.Heparin does not cross placental barrier and is not secreted in milk.

Adverse reactions:Rare anaphylactic reactions

Bleeding: avoid aspirin during heparin therapy

Thrombocytopenia: due to platelet aggregation and formation of heparin dependent antiplatelet antibodies. Improves after discontinuation of therapy, platelet counting before the start of therapy and during the therapy is recommended ,Stop the therapy if platelet count is below 100000/cmm

26

Low molecular weight heparins

26

Obtained by fractionation of native heparin.Molecular weight between 4000-65000.Advantages over native heparin are: 1.Absorbed more uniformly than native heparin2.Have longer duration of action t1/2= 43.Selectively inactivate factro Xa: their activity for thrombin is minimal.4.Have predictable anticoagulant effect5.Interact relatively less with platelets: fewer bleeding episodes.6.Less antigenic: less frequently causes thrombocytopenia & osteoporosis.

2727

Disadvantages :Are expensiveLMW heparins vary in their pharmacokinetic properties.Examples:Enoxaparin, dlateparin,tinzaparin,pamaparin,reviparin.Native heparin still remains the parenteral anticoagulant of

choice in ICU,operation theatre,patients with renal impairment.Fondaparinux:oSynthetic polysaccharide,binds to antithrombin.oEnhances inactivation of factor Xa.oT1/2 is 17 hrsSmall doses of heparin given SC for prophylaxis,have to monitored whole blood clotting time & activated partial

prothromboplastin time .No blood sample monitoring for LMW Heparin

28

Heparin antagonist (HA):

28

HA is a strongly basic compounds which reacts with strongly acidic groups of heparin. Thereby abolishing anticoagulant activity.Protamine Sulfate:1.Mixture of simple,low molecular weight polypeptide2.Found in fish sperm.3.Binds firmly to heparin and inactivate it.4.1mg of protamine neutralizes 100 units of heparin activity.5.After protamine injection patient should be observed for recurrence of bleeding as protamine sulfate is also a anticoagulant.6.Protamine IV may cause fall in BP,bradycardia,dyspnoea.7.It partially neutralizes LMWH.

29

Other Factor Xa inhibitors:Rivaroxaban:

29

1.It is orally active,direct selective factror Xa inhibitor.2.Used for prevention and treatment of arterial and venous thromboembolism.3.Does not require monitoring.

Danaparoid:oObtained from porcine intestinal mucosa.oGiven SC twice a day, for prophylaxis.oDoes not cause thrombocytopenia,has no antidote.oUsed as heparin substitute to prevent postoperative DVT.

30

Hirudine (Direct acting thrombin inhibitor)

30

1. Potent antithrombin polypeptide

2. Obtained from leech hirudo medicinalis

3. Now been synthesized by recombinant DNA technique.

4. Unlike heparin, it binds irreversibly to thrombin.

5. It inactivates free as well as fibrin-bound thrombin.

6. It doesn’t require antithrombin or other co-factor.

7. It not only prevents conversion of fibrinogen to fibrin but also blocks thrombin catalyzed platelet aggregation and activation of other clotting factors.

8. Its activity is monitored by same tests as of heparin.

9. No antidote available.

3131

Bivalirudin:1.Analogue of hirudin, with rapid onset and offset (due to reversible action).2.Safer than latter.Argatroban:1.Reversible direct thrombin inhibitor2.Alternative to hirudin.Dabigatran:It is prodrug (Dabigatran etexilate), orally active, direct inhibitor,As effectvie as enoxaparin,ADR are same as enoxaparin.Major adv: orally active without the need of coagulation monitoring.All direct thrombin inhibitors are used in patients with or at risk of developing heparin induced thrombocytopenia.

32

Human antithrombin concentrate:

32

Prepared from human plasma.It is used alone or in combination with heparin to treat patients with

rare hereditary disorder antithrombin III deficiency.

B. Oral anticoagulants (Slow acting)1. COUMARIN DERIVATIVES (SLOW ACTING)Effective orally (contrast to heparin)Bis hydroxy coumarin or dicumaral (first coumarin compound)Most commonly used drug is WARFARIN SODIUMAnticoagulant action:1. Vitamin K epoxide (inactive) convert to vitamin K reduced (active) by vitamin K epoxide reductase.2. Vitamin K (active) carboxylate the clotting factors II,VII,IX,X (active)3. Oral anticoagulant competes with vitamin K and inhibit vitamin K epoxide reductase.4. Slow acting: becz of long half life of clotting factors.5. Increase plasma antithrombin level

33

ADME:

33

1. Slow oral absorption, crosses placenta and secreted in

milk.

2. Action is slow, because they prevent the formation of

essential clotting factors by liver but do not destroy

the already circulating factors.

Adverse effects:

Bleeding:

Fetal toxicity

Cutaneous gangrene

34

Warfarin sodium:

34

1.It is employed as RAT POISON.2.It is racemic mixture.

3.Its advantages over coumarin (dicumaral /Bis hydroxycoumarin) arei. It is almost 99% orally absorbedii. Rapid onset of actioniii. Adverse effects are few, may inculde alopecia, urticaria, dermatitis.iv. Can cross placenta but not secreted in milk (long term warfarin use should be avoided in pregnancy).v. Major drawback is multiple drug interactions.

35

Mechanism of action: Warfarin

35

36

Drug interactions:

36

1.Inhibiting the platelet functions (aspirin,NSAID)

2.Stimulating hepatic microsomal catabolism of warfarin (Barbiturates,rifampicin,carbamazepine).

3.Displacing warfarin from protein binding (Sulfonamides,phenylbutazone,chlorpropamide etc)

4.Inhibiting metabolic clearance of warfarin (cimetidine,omeprazole,amiodarone)

37

Indandione derivatives:

37

These examples are PHENINDIONE,ANISINODIONE.Anticoagulant activity is similar to coumarin compounds.They are now OBSOLETE because of toxicity.

IN VITRO ANTICOAGULANTSPhysical methods: By cooling the bloodUse of Paraffin,collodion or silicone coated Pan for collectionCalcium complexing agents:Oxalates and Citrates: Potassium oxalate precipitate serum calcium as calcium oxalate and form calcium sodium citrate.The anticoagulant solution (B.P) contains 2.5 % sodium citrate in 0.9% saline.Potassium oxalate produces convulsions hence not used in vivo.

3838

EDTA: (Ethylene di amine tetra acetic acid)Chelating agent having greater affinity for calcium.Its sodium salt is used.

Heparin: Discussed earlier

39

Thrombolytics or Fibrinolytics1. Streptokinase2. Recombinant tissue type plasminogen activator3. Urokinase4. Acylated plasminogen/ streptokinase activator

40

Mechanism of Fibrinolysis:

All thrombolytic agents are directly

or indirectly plasminogen activator.

CLASSIFICATION:

1. Fibrin specific thrombolytic agents

Alteplase,Reteplase,Tenecteplase

2. Fibrin non-specific thrombolytic agents

Streptokinase, Anistreplase, Urokinase.

All are directly acting thrombolytic agent except Steptokinase.

Pharmacokinetic profile,patients tolerance and disease state will be consider to select the thrombolytic agent.

40

4141

Streptokinase:

1.Obtained from Beta haemolytic Steptococci group C.2.It is inactive as such: BUT when combines with plasminogen,the plaminogien-STC complex is ACTIVE.

3.Causes conversion of plasminogen to plasmin.

4.Antistreptococcal antibodies of past infection inactivate it.

5.It may cause hypersensitivity reactions and anaphylaxis.

6.Fever,hypotension and arrhythmias are reported.

7.Used in DVT, due to availability of other fibrinolytics it is not used in developed countries.

8.Being least expensive still widely used in developing countries.

42

Urokinase:

42

1.Obtained from human urine.2.Now obtained from cultured human renal cells3.Potent direct plasminogen activator4. It is non-antigenic,non-pyrogenic,non -allergic. (differ

from STC).5. Lacks fibrin specificity and very expensive.6. Its use is followed by heparin and latter oral

anticoagulants.7.Used to lyse fibrin or blood deposit in anterior

chamber of eye.8.Used in patient in whom STK has been used for an

earlier episodes.9. Limited use because of availability of newer

fibrinolytics.

43

Alteplase (Recombinant plasminogen activator)

1. Produced by recombinant DNA technology from human tissue

culture.

2.Specifically activates gel phase plasminogen already bound to fibrin, and has little action on circulating plasminogen.

3.It is rapidly cleared by liver and has a plasma t1/2 of 4 to 8

min.

4.Because of the short t1/2, it needs to be given by slow IV

infusion and often requires heparin coadministration.

5.It is nonantigenic, but nausea, mild hypotension and fever may occur.

6.It is expensive.

44

Rateplase:

1. It is modified form of rt-PA, longer acting.

2. somewhat less specific for fibrin bound plasminogen.

3.The longer duration of action enables bolus dose administration (10 mg over 10 min repeated after 30 min).

Tenecteplase:1. It is a mutant variant of rt-PA with higher fibrin

selectivity and longer duration of action.

2.The clinical efficacy and risk of bleeding with reteplase and tenecteplase are similar to alteplase.

45

Uses of fibrinolytics:

1. Acute myocardial infarction

2. Deep vein thrombosis

3. Pulmonary embolism

4. Peripheral arterial occlusion

5. Stroke

46

Antiplatelet agent

47

Process of Platelet Plug formation...

Damage to vascular endothelium Release of reactive proteins like collagen and von Willebrand factor (vWF)

React respectively with platelet GPIa, and GPIb receptors

Platelets are activiated

Release of proaggregator. and vasoconstrictor mediators (TXA2, ADP and 5-HT)

The platelet GPIIb/III, receptor undergoes a conformational change favouring binding with fibrinogen

Induces platelet aggregation and platelet plug is formed

48

Control of intravascular thrombus formation:

In veins, due to sluggish blood flow, a fibrinogen tail is formed

which traps RBCs "the red tail'. (Anticoagulants are more

effective in venous thrombosis)

In arteries platelet mass is the main constituent of the thrombus.

(Antiplatelet drugs are more useful in arterial thrombosis).

Prostacyclin (PGI2), synthesized in blood vessels,(strong inhibitor of platelet aggregation).

A balance between TXA2, released from platelets and PGI2

released from vessel wall appears to control intravascular thrombus formation.

Platelets also play a role in atherogenesis.

49

AntiplateletAntiplatelet agentagent::1.Prostacyclin PGI22. Inhibitor of TXA2 formation: asprin

3.ADP receptor antagonist: Ticlopidine,Clopidogrel

4.Phosphodiesterase inhibitor: Dipyridamole

5.Glycoprotien IIb/IIIa antagonist: Abciximab

50

Physiology of platelet aggregation:

51

Role of vWF and Gp receptors:

52

Mechanism of action of antiplatelet agents:

53

Prostacyclin (PGI2)

It is naturally produced by endothelial cells of blood vessels.

Effects: causes vasodilation,inhibitig platelet aggregation.

Uses: during hemodialysis and to treat pulmonary hypotension.

Very unstable,short half life of 3 mints.

54

TXA2 inhibitor: Aspirin

In low dose selectively

inhibit synthesis of

TXA2,higher dose

also inhibit

prostacyclin formation.

55

Uses of Aspirin:1. Decreaseg the incidence of CHD.2. Preventing MI in patients with angina.3. Acute cronary syndrome where immediate platelet

inhibition is desirable.4. Patients undergoing cronary bypass surgery.5. Preventing stroke in CVD.6. Preventing ischemic limb complication.7. Preventing reinfarction in pateints having MI.8. Preventing pre eclampsia in pregnant women but should

be given between 12th to 16th weeks of pregnancy.9. In hypertensive patients it is avoided.10.Can cause G.I Bleeding.

56

57

Dazoxiben:1. It is substituted imdiazole.2. Selectively blocks production of TXA2.3. Without affecting PGI2.4. ASPRIN IS SAFER AND FAR SUPERIOR.

Ticlopidine: (ADP receptor antagonist)

1. Thienopyridine derivative.2. Active metabolite is ADP antagonist.3. Oral onset of action delayed for hours.4. Slightly more effective than aspirin but more toxic than

aspirin.

58

ClopidogrelClopidogrel: (: (ADPADP receptorreceptor antagonistantagonist))1.Chemically related to ticlopidine.

2. Irreversibly block P2Y12 receptor present on platelet responsible for platelet aggregation.

3.As compare to aspirin it is more expensive.

4.Combination with aspirin is synergestic only for acute complications.

5.Combination may give excessive bleeding.

6.Alternative P2Y12 antagonists are developed with fast onset of actions like newer Thienopyridines (Prasugrel, Ticagrelor,cangrelor.)

59

Dipyridamole:Dipyridamole:(Phosphodiesterase inhibitor)(Phosphodiesterase inhibitor)

It is vasodilator.

Reversibily inhibit platelet phosphodiestrase enzyme. leading to increase in cAMP. Decrease in cystosolic calcium and inhibit platelet aggregation.

Use:

As adjuvant to warfarin in patients with artificial heart valves.

60

Glycoprotien IIa/IIIb antagonist:

1. A monoclonal antibody against the platelet

receptors eg: Abciximab

2. Synthetic inhibitor eg: Tirofiban (competative blocker of receptor)

Abciximab:

have synergestic effect with aspirin and

heparin. effect last for 48 hrs.

Tirofiban and Eptifibatide: competative inhibitor.

plasma half life is 2to 2.5 hrs.