PowerPoint Presentation - Anticoagulants and Thrombolytics
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Objectives
To learn how Blood Clots are formed.
How the blood clots are broken down ?
What drugs can be used to regulate
clotting ?
How to rectify clotting deficiencies
Classes of Drugs
Prevent coagulation
Dissolve clots
Prevent bleeding and hemorrhage Hemostatic
Overcome clotting deficiencies
(replacement therapies)
Blood Clotting
Vascular Phase
Platelet Phase
Coagulation Phase
Fibrinolytic Phase
Vascular Phase
Vasoconstriction
Exposure to tissues activate Tissue
factor and initiate coagulation
Tissue Factor
Platelet phase
blood vessel wall (endothelial cells) prevent platelet
adhesion and aggregation
platelets contain receptors for fibrinogen and von
Willebrand factor
after vessel injury Platelets adhere and aggregate.
Release permeability increasing factors (e.g.
vascular permeability factor, VPF)
Loose their membrane and form a viscous plug
Coagulation Phase
Two major pathways
Intrinsic pathway
Extrinsic pathway
Both converge at a common point
13 soluble factors are involved in clotting
Biosynthesis of these factors are dependent on Vitamin K1
and K2
Normally inactive and sequentially activated
Hereditary lack of clotting factors lead to
hemophilia -A
Intrinsic Pathway
All clotting factors are
Extrinsic Pathway
Initiating factor is
within the blood
outside the blood
vessels
vessels - tissue factor
Clotting slower
Activated partial
thromboplastin test
(aPTT)
Clotting - faster - in
Seconds
Prothrombin test (PT)
Intrinsic Pathway
Extrinsic Pathway
Tissue Injury
Blood Vessel Injury
Tissue Factor
XIIa
XII
Thromboplastin
XIa
XI
IXa
IX
Xa
X
Factors affected
By Heparin
VIIa
Prothrombin
Vit. K dependent Factors
Affected by Oral Anticoagulants
Fibrinogen
XIII
VII
X
Thrombin
Fribrin monomer
Fibrin polymer
Anticoagulant drugs to treat
thromboembolism
Drug Class
Anticoagulant
Parenteral
Prototype
Heparin
Action
Inactivation of clotting
Factors
Effect
Prevent venous
Thrombosis
Anticoagulant Warfarin Decrease synthesis of
Oral
Clotting factors
Prevent venous
Thrombosis
Antiplatelet
drugs
Aspirin
Prevent arterial
Thrombosis
Thrombolytic
Drugs
Streptokinase Fibinolysis
Decrease platelet
aggregation
Breakdown of
thrombi
Heparin
Sulphated carbohydrate
Different sizebovine lungs
Administration - parenteral- Do not inject IM only IV or deep s.c.
Half-life 1 - 5 hrs - monitor aPTT
Adverse effect: hemorrhage
Antidote : protamine sulphate
Heparin mechanism of action
Heparin
Antithrombin III
Thrombin
Oral anticoagulants
Examples: Coumarins - warfarin, dicumarol
Structurally related to vitamin K
Inhibits production of active clotting factors
Clearance is slow - 36 hrs
Delayed onset 8 - 12 hrs
Overdose - reversed by vitamin K infusion
Can cross placenta - do not use during late
pregnancies
Mechanism of action
Descarboxy Prothrombin
Prothrombin
Reduced Vitamin K Oxidized Vitamin K
NAD
NADH
Warfarin
Normally, vitamin K is converted to vitamin K epoxide in the liver.
→This epoxide is then reduced by the enzyme epoxide reductase.
→The reduced form of vitamin K epoxide is necessary for the synthesis of many
coagulation factors (II, VII, IX and X, as well as protein C and protein S).
→Warfarin inhibits the enzyme epoxide reductase in the liver, thereby inhibiting
coagulation. )(عبدهللا المطيري
Warfarin Side Effect
Severe Side effects:
•Severe bleeding
•Bleeding from the rectum or black stool
•Skin conditions such as hives, a rash or itching
•Swelling of the face, throat, mouth, legs, feet or hands
•Bruising that comes about without an injury you remember
•Chest pain or pressure
•Nausea or vomiting
•Fever or flu-like symptoms
•Joint or muscle aches
•Diarrhea
•Difficulty moving
•Numbness of tingling in any part of your body
•Painful erection lasting four hours or longer
Warfarin Side Effect
Other less serious warfarin side effects:
•Gas
•Feeling cold
•Fatigue
•Pale skin
•Changes in the way foods taste
•Hair loss
Drug interaction- with Warfarin
Category
Drugs that Increase
Warfarin Activity
Mechanism
Representative Drugs
Decrease binding to
Albumin
Aspirin, Sulfonamides
Inhibit Degradation
Cimetidine, Disulfiram
Decrease synthesis of
Clotting Factors
Antibiotics (oral)
Drug interaction with Warfarin
Drugs that promote
bleeding
Drugs that decrease
Warfarin activity
Inhibition of platelets
Aspirin
Inhibition of clotting
Factors
heparin
antimetabolites
Induction of metabolizing
Enzymes
Barbiturates
Phenytoin
Promote clotting factor
Synthesis
Reduced absorption
Vitamin K
cholestyramine
colestipol
Antiplatelet drugs
Example: Aspirin
Prevents platelet aggregation /adhesion
Clinical use - prevents arterial thrombus
Myocardial infarction (MI), stroke, heart valve
replacement and shunts
Other antiplatelet drugs are Dipyridamole, sulfinpyrazone and
Ticlopidine
Mechanism of action
Aspirin inhibits cyclooxygenase (COX)
COX is a key enzyme involved in the
synthesis of thromboxane 2
(prostaglandins)
Inhibits platelet aggregation
Prophylactic use of Aspirin
Low dose daily.
Prevents ischemic attack (ministroke) and MI
335 mg/day reduced the risk of heart attack in
patients over 50
More than 1000 mg/day NO EFFECT
Contraindication - DO NOT give to patients with
glucose 6-PO4 dehydrogenase deficiency
Fibrinolysis
Enhance degradation of clots
Activation of endogenous protease
Plasminogen (inactive form) is
converted to Plasmin (active form)
Plasmin breaks down fibrin clots
Fibrinolysis
Exogenously administered drugs
Streptokinase - bacterial product
○ - continuous use - immune reaction
Urokinase - human tissue derived –
○ no immune response
Tissue plasminogen activator (tPA) - genetically
cloned
○ no immune reaction
○ EXPENSIVE
Drug preparations : To reduce clotting
Heparin (generic, Liquaemin sodium)
Parenteral - 1000 - 40,000 U/ml
Warfarin (generic , Coumadin)
Oral : 2 - 20 mg tablets
Dipyridamole (Persantine)
Oral : 25,50,75 mg tablets
Drug preparations : to lyse clots
Alteplase recombinant (tPA, Activase)
20, 50 mg Lyophilized powder - reconstitute for iv
streptokinase (Kabikinase, streptase)
Parenteral : 250000 - 1.5 million units per vial .
Lyophilized powder. Reconstitute for iv
Urokinase ( Abbokinase)
Parenteral : 250000 units per vial. Powder to
reconstitute to 5000 u/ml for injection
Drug preparations: clotting deficiencies
Vitamin K ( Phytonadione (K1), Mephyton
Oral : 5 mg tablets
Plasma fractions - for hemophilia
Antihemophilic factor ( VIII, AHF)
Parenteral
Factor IX complex (konyne HT, proplex T)
Parenteral : in vials
Drug preparations : to stop bleeding
Systemic use : aminocaproic acid (Amicar);
Tranexamic acid (cyclokapron),Vitamin K
Local adsorbable drugs
Gelatin sponge (Gelfoam)
Gelatin film
Oxidized cellulose ( Oxycel)
Microfibrillar collagen (Avitene)
Thrombin