Drugs For Coagulation Disorders

ANTIPLATELETS, ANTICOAGULANTS, THROMBOLYTICS I. Process of blood coagulation & thrombus formation Blood vessel injury

Vasoconstriction

Blood loss into tissues

Intrinsic pathway to clot formation

Extrinsic pathway to clot formation

Platelet adhesion to injured wall of bv & platelet aggregation

decrease blood flow at site of injury

compression of injured bv

platelet plug

blood clot thrombus

Decrease blood loss at site of injury

 Final step of clot formation: Prothrombin

thrombin Fibrinogen

Fibrin

 Clot dissolution: Plasminogen

plasmin (fibrinolysin) Fibrin clot

dissolution of clot

clot

II.

Drugs affecting Blood Coagulation A. Antiplatelets • aspirin * • clopidrogel (Plavix) • ticlopidine (Ticlid) • dipyridamole B. Anticoagulants (blood thinners) • heparins* Heparin sodium o Low- molecular weight heparins ( LMWH )  danaparoid  hirudin  daltaparin o

• warfarin (Coumadin)* • Dicumarol C. Thrombolytics ( clot busters) • streptokinase*

• Urokinase • Altepase (tissue plasminogen activator )

A. Antiplatelets • aspirin * MOA: suppress platelet adhesion& aggregation ---> prevent thrombosis in ARTERIES Indications: 1. prevent MI or stroke in pxs with familial history 2. prevent repeat MI 3. prevent stroke in pxs with transient ischemic attacks (TIAs) other uses: • peripheral arterial disease • after angioplasty & stent replacement • after coronary artery bypass graft (CABG) • atrial fibrillation SE: 1. bleeding (MC) • petechiae • ecchymosis • epistaxis 2. headache, dizziness & weakness

• tarry stools • hematemesis • bloody urine

3. GI distress 4. skin rash 5. tinnitus, hearing loss Contraindications (CI): • pregnancy & lactation • bleeding disorders o blood dyscrasias o peptic ulcer dse (PUD) o CVA o severe hypertension • recent surgery • closed head injuries

:

Drug interactions: anticoagulants, thrombolytics, herbs (garlic , gingko) B. Anticoagulants (blood thinners) • heparin* • warfarin (Coumadin)* MOA: interfere with clotting cascade & thrombin formation ---> prevent formation of new blood clots & keep existing blood clots from grower larger.  Heparin • MOA: heparin binds with antihthrombin Prothrombin

thrombin fibrinogen

Fibrin

clot

• poorly absorbed orally --->IV (for acute thrombosis) or SC ( for prophylaxis) • onset of action : immediate t1/2 = 1-2 hrs • donot cross placenta • Indications: 1. deep vein thrombosis (DVT) 2. pulmonary embolism 3. coronary artery disease (CAD)

4. atrial fibrillation 5. TIAs 6. prevent clotting in blood samples & in dialysis & venous tubing

• CI: 

hemophilia



peptic ulcer



 severe HPN severe renal / liver dse



dissecting aneurysm

 prolongs clotting time:  monitor activated partial thromboplastin time (aPTT) – 1.5 to 3x control value (60-70sec)  monitor partial thromboplastin time (PTT) – 1.5 -2x control value (60-70 sec)  antidote for heparin overdose : protamine sulfate

 warfarin (coumadin) MOA: inhibit liver synthesis of Vitamin K --> decrease clotting factors --> decrease clot formation • • • •

well absored orally onset of action : 3 days t1/2= 3 days effects last for 4 – 5 days cross placenta & breastmilk

• Indications: 1. 2. 3. 4.

atrial fibrillation artificial heart valves valvular heart disease tx & prevent thrombosis & embolization after acute MI or pulmonary embolism

• prolongs clotting time:  monitor prothrombin time (PT) - 1.5 – 2.5 x control value (11- 15 sec)  monitor PT/ International normalized ratio (INR) – 2 – 3 (1.3-2.0) • antidote for warfarin overdose: Vitamin K1 (phytonadione) SE/ Adverse effects of anticoagulants: 1. bleeding/ hemorrhage 2. GIT upset 3. alopecia, dermatitis, BM depression, priapism CI of warfarin:: • bleeding tendencies • pregnancy • Severe Liver /kidney dse

• Acute MI • alcoholism

Drug interactions: esp with warfarin  Aspirin  NSAIDS  Phenytoin  Cimetidine  Antibiotics  Some antidysrhythmics  Grapefruit juice

C. Thrombolytics ( clot busters) • streptokinase* MOA:

thrombolytics Plasminogen

plasmin (fibrinolysin) Fibrin clot

Indications: 1. 2. 3. 4.

acute MI pulmonary embolism ischemic stroke to open clotted IV catheters

SE/adverse effects: 1. bleeding tendencies 2. cardiac arrhythmias 3. hypotension 4. fever CI: same as anticoagulants Drug interactions: antiplatelet , anticoagulants Antidote for thrombolytic overdose: aminocaproic acid

dissolution of clot