ANTI-HEMOSTATIC DRUGS IN VETERINARY PRACTICE

ANTIHAEMOSTATICS

ASSIGNMENT PRESENTED TO

DR SUJITH S

ASST PROFESSOR , DEPT OF VPT ,

COVAS , POOKODEPRESENTED BY

DR SINDHU K

MVSc SCHOLAR

AGENTS WHICH REDUCES HEMOSTASIS / BLOOD CLOTTING

1) ANTICOAGULANTS

In vitro & systemic

2) THROMBOLYTICS

Plasminogen activators

3) ANTIPLATELET DRUGS

COX inhibitors , glycoprotein IIa/IIIb inhibitors , thromboxane inhibitors & ADP inhibitors

Components of hemostatic System:-

1) Platelets

2) Plasma proteins – Coagulation & Fibrinolytic factors & inhibitors

3) Vessel wall itself(endothelium)

Steps of normal homeostasis :-

1} platelet plug formation• Adhesion, activation, aggregation

2}Fibrin clot formation• Coagulation - intrinsic

- extrinsic

3}Dissociation of clot

Vascular Injury

Exposure of collagen and vWF Tissue factor exposure

Platelet adhesion and release

Activation of coagulation

Platelet recruitment and activation

Thrombin generation

Fibrin formationPlatelet aggregation

Platelet – fibrin thrombus

ANTI COAGULANTS

1] In vitro use

To prevent clotting of blood for transfusion or diagnostic use

2] In vivo use

To prevent development & enlargement of thrombi

IN-VITRO ANTICOAGULANTS

• For lab purposes – sodium oxalates , sodium fluoride , EDTA

• For blood transfusion – ACD solution , CPDA-1 solution

OXALATES

1} sodium oxalate – combines with blood calcium forming insoluble calcium oxalate rendering calcium unavailable for blood coagulation

Dose – conc of 20 % @ level of blood

0.01 ml / 1 ml blood ( 2mg/ml)

ALL OXALATE SALTS ARE TOXIC

Contraindicated – blood transfusion

-- systemic use

SODIUM FLUORIDE

• Excellent anticoagulant for blood glucose studies bcoz it interferes with enzymes involved in glycolysis

• It acts as preservative

• Dose 2.5 mg / ml of blood for blood glucose preservation

ETHYLENE DIAMINE TETRA ACETIC ACID

• EDTA ( edetate disodium , USP )

MOA – Na & K salts of EDTA chelates blood calcium thus preventing clotting

• Lab application

1} hematological count { thrombocyte count }

bcoz Cellular details preserved

Dose – 1 mg / 5 ml of blood

0.01 ml of 2 % EDTA solution / ml of blood

BLOOD TRANSFUSION

1] Acid Citrate Dextrose , USP

Sodium citrate – 25 g

Citric acid – 8 g

Dextrose – 24.5 g

Distilled water to make volume of 1000 ml

Dose – at level of 15 ml / 100 ml of blood

Toxicity in dogs should not cross 286mg/kg

`2] Citric Phosphate Dextrose Adenine CPDA-1

In DOGS maintains high levels of erythrocyte post transfusion

viability up to 20 days

3] Heparin

In cats - To collect small quantity of blood ( 50 ml )for transfusion

Lab purpose : 8 – 10 units of heparin / ml of blood

Blood transfusion : 4 – 6 units of heparin / ml of blood

SYSTEMIC ANTICOAGULANTS

1} Heparin & related compounds

2} Inhibitors of vitamin K

3} Direct inhibitors of coagulation factors

4} Miscellaneous anticoagulants

HEPARIN ( HEPARIN SODIUM , USP )

• Pharmaceutical graded heparin is prepared from bovine lung tissue or porcine intestinal mucosa

• It is a heterogenous mixture of anionic sulfated mucopolysaccharide with molecular weight ranging from 1200 – 40000 daltons.

• Sodium salts used in vivo.

• Calcium salts , potassium salts – therapeutic use.

MOA

• Anti coagulatory effect of heparin – the reversible binding of heparin to AT III , a protease inhibitor & Heparin Co factor II

• Binded heparin accelerates the velocity of interaction between coagulant inhibitory factors & clotting factors

• LMWH – inactivates only factor Xa

• HMWH – inactivates thrombin & blocks conversion of fibrinogen to fibrin , neutralizes activated factor IX

P K & P D

• Administered dose of heparin bounds extensively: endothelial cells

macrophages

plasma proteins

Stored pools ~> saturated ~> free heparins ~>plasma ~> excretion kidney

Metabolism – liver

- Reticulo endothelial system

CLINICAL INDICATION

• Prevention / treatment of venous thrombosis ( red thrombus )

• Pulmonary embolism

• Management of DIC

• Arterial fibrillation with embolization

Eg: feline cardiomyopathy

• Other potential coagulable states

Eg: cushing`s disease

nephrotic syndrome

cardiomyopathy

GUIDE LINE FOR HEPARIN DOSAGE

1} High dose heparin therapy

Aims to increase APTT 1.5 – 2.5 times base line & ACT 1.2 – 1.4 times base line

Initial high loading dose is beneficial

Regular & frequent monitoring of clotting time s essential

Clinical indication – treatment of established THROMBOEMBOLI

Dogs : 150 – 250 U / kg TID

Cats : 250 – 375 U / kg TID

2} LOW DOSE HEPARIN THERAPY

Dogs : treatment & management of Heart worm infestation

Initial dose 100 – 200 U / kg i/v followed by 50 U / kg every 3 hours

Maintenance dose 40 – 80 U / kg TID s/c

Cats : treatment of feline cardiomyopathy

200 U / kg s/c TID

Horses : management of DIC

high grade DIC : 80 – 100 U / kg i/v after 4-5 hr repetation

low grade DIC : 25 – 40 U / kg s/c BID / TID daily

MANAGEMENT OF DIC ~ DISSEMINATED INTRAVASCULAR COAGULOPATHY

Heparin + blood / plasma

Low dose regimen for management

Small animals : 75 U / kg TID

Horses : 25 – 100 U / kg TID

Effect on APTT = minimum

LOW MOLECULAR WEIGHT HEPARINS

• Are short chain of polysaccharide with molecular weight of 1000-10000 Da

• Isolated from standard heparin by techniques

- Gel filtration chromatography

- differential precipitations with ethanol

Advantages: better absorption from s/c injection

: prolonged elimination half life

: lower incidences of hemorrhagic complications

MOA

• LMWH selectively inhibit factor Xa with little effect on thrombin , Factor II ~> result is little effect on APTT & whole blood clotting time

• LMWH less anti platelet action

• Commercial preparations – Ardeparin , Bemiparin , Dalteparin ,

Enoxaparin , Reviparin , Nadroparin ,

Tinzaparin

HEPARINOIDS

• Non heparin naturally occurring & synthetic sulphated glycosaminoglycans which posses heparin like anticoagulant action

1} DANAPAROID (Orgaron*)

Mixture of non heparin glycosamines isolated from porcine intestinal mucosa

Orgaron* consists ~ heparin sulphate 80 %

~ dermatan sulphate 8 -16 %

~ chondroitin sulphate < 8.5 %

MOA

• Acts mainly by enhancing the inhibition of factor Xa by antithrombine

• Danaproid exerts a strong catalytic effects on the inactivation of factor Xa than on the inactivation of thrombin

Clinical indications

• Prevention of DEEP VEIN THROMBOSIS ( DVT ) following orthopaedic , major abdominal & thoracic surgery

• Patients with positive diagnosis of non hemorrhagic stroke

OTHER DRUGS

1] drotrecogin alfa

2] dextran sulphate

3] sulodexide

VITAMIN K ANTAGONISTS

• Inhibitors of vitamin K often called as ORAL ANTICOAGULANTS

• VIT K antagonists are active ORALLY (only IN VIVO )

• Studies in veterinary medicine focused primarily on their TOXIC effects rather than on therapeutic indications

TYPES

1} Coumarin derivatives

2} Indanedione derivatives

COUMARIN DERIVATIVES

• Coumadins are synthetic oral anticoagulants derived from the molecule 4 hydroxycoumarin

1} BISHYDROXYCOUMARIN – first oral AC synthesized by LINK (1943-44)

Its a derivative of moldy / spoiled sweet clover which is responsible for hemorrhagic disease in cattle in USA

2} WARFARIN SODIUM (USP)

2nd compound synthesized commercially

WARFARIN: MOA

• Inhibiton of hepatic synthesis of vit K dependent clotting factor ~ Prothrombin

~ Factor VII , IX , X

~ anticoagulant protein C & S

Carboxylation results in the oxidative inactivation of vit K

Warfarin inhibits vit K epoxide reductase enzyme & interfere with regeneration of active form of vit K thereby inhibiting synthesis of prothrombin & factor VII , IX , X

`

• Warfarin acts as AC only IN VIVO bcoz they act indirectly by interfering with synthesis of clotting factors

• AC effects develops over several hours but peak plasma level occurs in 1 hour after oral administration onset takes 6 -12 hours with full benefits realized after (2-3 days) & long duration of action (4-7 days)

• bcoz of persistence of factors synthesized before drug administration & of long half life

• Rapidly & completely absorbed from intestine

• Metabolised in liver ~ inactive metabolites cytochrome P450 system

ADVERSE EFFECTS

• Acute internal bleeding/hemorrhage

• Clinical signs ~ anaemia , thrombocytopenia , hematuria etc

• Hemorrhages in brain & spinal column ~ ataxia , paresis , convulsions

• Periarticular hemorrhages ~ lamness , joint swelling , pain

LAB CONTROL

1} the quick test

2} the one stage prothrombin time

CLINICAL INDICATIONS

• Prophylaxis of venous thrombosis & Aortic/ pulmonary thromboembolism

Horses : to relieve the clinical signs of NAVICULAR DISEASE

Dose @ 0.02 mg/kg PO once daily

Dogs : for prevention of recurrence of thrombotic conditions

Dose @ 0.1 – 0.2 mg/kg PO once daily

INDANEDIONE DERIVATIVES

• Are derivative of indane-1,3-dione

• Structurally related to coumarins & produce anticoagulation activity by mechanism involving ANTAGONISM OF VITAMIN K

• Reports to cause kidney damage, sensitivity reactions, leucopenia in humans. Hence retricted drugs category

• Use in vety practice not reported yet

Eg: Anisindione , phenindione , clorindione , diphenadione

DIRECT INHIBITORS OF COAGULATION FACTORS

1} Direct inhibitors of factor Xa – Xabans

-- Rivaroxabans

2} Direct inhibitors of coagulation factor II – hirudin

-- bivalirudin

-- desirudin & lepirdin

3} Direct thrombin inhibitors – argatroban

-- dabigatran

END OF TOPIC - ANTICOAGULANTS

DISCUSSIONS

THROMBOLYTICS

• Drugs that enhances the conversion of the inactive precursor plasminogen to the active fibrinolytic enzyme plasmin

• 2 phases Plasminogen ~ plasma/soluble phase

• ~ gel phase

• Dissolves both physiologic as well as pathogenic thrombus = TOXIC ,producing hemorrhage = major side effect

MOA• When plasminogen activating agents + clot = activation of

fibrin bound gel phase plasminogen to plasmin locally with selective fibrinolysis

• Instead soluble phase plasminogen circulating in systemic blood also activated

• Adverse effect = increased tendency for systemic bleeding

• Plasmin formation occurs through out circulation = overactivation of plasminogen , neutralizing endogenous antagonist to plasmin a2 ANTIPLASMIN

THROMBOLYTIC DRUGS – MECHANISM OF ACTION




FIRST GEN : STREPTOKINASE

• Streptokinase is a protein obtained from group C BETA HEMOLYTIC STREPTOCOCCI

• Effective & inexpensive clot dissolving drug ~ MI

• ~ Pulmonary embolism

• MOA :acts as plasminogen activator = enhances production of plasmin by forming an active non covalent 1:1 complex (streptokinase : plasminogen complex )

• Plasmin catalyzes degradation of plasma proteins = clotting factor FIBRINOGEN & factor V , VII

ADVERSE EFFECT

• Foreign protein = Antigenic reactions

• 2nd time use = hypersensitivity & Anaphylaxis

• Over dosage = plasminogen depletion & SK resistance

• Treatment over-dosage FRESH PLASMA /AMINOCAPROIC ACID

CLINICAL INDICATIONS

• Used locally as powder , infusion or irrigation of wounds which don’t responds for antibacterial therapy – burns , ulcers , chronic eczema , ear hematomas , otitis externa , osteomyelitis , chronic sinusitis

• Parentrally ~ eczema , dermatitis , hematoma , trauma & pneumonia

• Prophylaxis ~ reduction of post operative adhesions

• Dogs: 5000 – 10,000 U (total dose) IM IV in 2 divided doses 5 days

• Large animals : 5000 – 10,000 U / 45 kg BW , IM IV 2 divided dose 5 – 6 days

SEC GEN : PLASMINOGEN ACTIVATORS

• Tissue plasminogen activators

• Alteplase

• Reteplase

• Urokinase

• Streptodornase

OTHER DRUGS ~ ancrod

~ fibrinolysin

MOA

• It catalyzes conversion of plasminogen to plasmin

• Selective action towards the plasminogen bound to fibrin & low affinity for free plasminogen

• Thus fibrinolysis to the formed clot , with out unwanted degradation of other proteins

Clinical indication

1} thromboembolic strokes

2} deep vein thrombosis

3} pulmonary embolism to clear a blocked artery

`

• ALTEPLASE – treatment of aortic thromboembolism

Cats : 0.25 – 1 mg/kg/hour , i/v infusion for total dose of 1-10 mg/kg

Dogs : 0.01 microgram/kg/min , i/v infusion for 30 min

• UROKINASE – to prevent post operative lesions

Dogs : 5000 – 10,000 units/kg , intra-peritoneal lavage

END OF TOPIC - THROMBOLYTICS

DISCUSSIONS

ANTITHROMBOTIC DRUGS




THE ROLE OF PLATELETS





Antiplatelet drugs

Acetylsalicylicacid (aspirin)

P2Y12 antagonists

Dipyridamole GPIIb/IIIaantagonists

Used widely in patients at risk of

thromboembolic disease

Beneficial in the treatment and

prevention of ACS and the prevention of thromboembolic

events

Secondary prevention in

patients following stroke, often in

combination with aspirin

Administered intravenously, are effective during percutaneous

coronary intervention (PCI)

COX INHIBITORS• Aspirin ~ NSAID

• MOA = irreversibly inactivates cyclooxygenase enzyme to produce pharmacological effects

Reduces synthesis of thromboxane A2 = potent vasoconstrictor & inducer of platelet aggregation

• Irreversibly acetylate thromboxane synthase , enzyme responsible for thromboxane synthesis

• Low dose = effective in reducing platelet aggregation

• High dose = blocks synthesis of prostacyclin reducing over all anti aggregatory effect

Plaque Disruption

Collagen vWF

Platelet adhesion and secretion

Aspirin

Thrombin generation

Abciximab Eptifibatide

Tirofiban

Platelet aggregation

Platelet recruitment and activation

X COX-1

TXA2ADPX

GPllb / llla activation

X

CYCLOOXYGENASE INHIBITORS – MECHANISM OF ACTION

ACETYLSALICYLIC ACID – MECHANISM OF ACTION




GLYCOPROTEIN II B / III A INHIBITORS

• NEW CLASES of potent platelet aggregation agonists

• MOA – acts by blocking glycoprotein II b / III a receptors present on surface of platelets

• Glycoprotein II b / III a complex functions as receptor = vWB factor through which agonists collagen , thrombin , thromboxanes , ADP induces platelet aggregation

• Drugs:

1} Abciximax – treatment of ANGIOPLASTY

2} EPTIFIBTIDE

2} tirofiban

GPIIB/IIIA-RECEPTOR ANTAGONISTS – MECHANISM OF ACTION





THROMBOXANE INHIBITORS

• Acts through inhibition of thromboxane synthetase = decreases synthesis of TXA2 thus prevents platelet aggregation

• Elevates endogenous cAMP in the platelets by inhibiting phosphodiesterase enzyme

• Blockade of cellular reuptake of adenosine into platelets ,RBC & endothelial cells =increased extra cellular concentration of adenosine

,

1} DIPYRIDAMOLE

As synergistic with ASPIRIN

With WARFARIN – to decrease the incidence of thromboembolisim in patients with PROSTHETIC HEART VALVES

2}DAZOXIBEN

3}PICOTAMIDE

4}TERUTROBAN

MISCELLANEOUS DRUGS• CILOSTAZOL : phosphodiesterase inhibitor = intracellular

concentration of cAMP = increase in PK-A = inhibition of platelet aggregation & arterial vasodilator effect

Treatment – muscular pains due to cramps , numbness or fatigue

• TIMOLOL ( b adrenoceptor blocker )

synergizes action of low dose aspirin

• SULFINPYRAZONE uricosuric drug related to phenylbutazone

Inhibits COX enzyme = blocks production of prostanoids

REFERENCES

• H RICHARD ADAMS Veterinary pharmacology and therapeutics, 8th edition.

• GOODMAN & GILMAN`S The pharmacological basis of therapeutics, 11th edition.

• HS SANDHU Essentials of veterinary pharmacology and toxicology, 2nd edition.

• GOOGLE IMAGES

• ONLINE SEARCH RELATED TOPICS

THANK YOU

Education

ANTI-HEMOSTATIC DRUGS IN VETERINARY PRACTICE