HEMATOLOGY AND ONCOLOGY- Pharmacology Flashcards
Mechanism of action of Heparin
Cofactor for the activation of antithrombin, ↓ thrombin, and ↓ factor Xa
Clinical use of Heparin
Immediate anticoagulation for Pulmonary embolism, acute coronary syndrome, MI, deep venous thrombosis (DVT)
Can heparin be used during pregnancy?
Yes. (does not cross placenta)
What need to be followed when using Heparin?
PTT
Secondary effects due to use of Heparin
Bleeding, thrombocytopenia (HIT), osteoporosis, drug-drgu interactions
What is the rapid reversal antidote for Heparin?
Use protamine sulfate
How does protamine work?
Positively charged molecule that binds negatively charged heparin
Which are low molecular weight heparin?
Enoxaparin
Dalteparin
Which is the benefict of Low weght heparin?
Act more on factor Xa, have better bioavilability and 2-4 times longer half life
How is low molecular weight heparin administered?
Subcutaneously
Does low molecular weight heparin require monitoring?
No
Which is the risk when using low molecular weight heparin?
Not easily reversible
What is HIT?
Heparin Induced Thrombocytopenia
Pathophysiology of Heparin Induced Thrombocytopenia
Development of IgG antibodies against heparin bound to platelet factor 4. Antibody- Heparin- PF4 coplex activates platelets→ Thrombosis and thrombocytopenia
Derivates of hirudin
Argatroban, bivalirudin
Which anticoagulant is used by leeches?
Hirudin
What is the effect of Argatroban, bivalirudin?
Inhibit thrombin directly
When is recommended to use Argatroban, bivalirudin?
Used instead of heparin for anticoagulating patients with Heparin Induced Thrombocytopenia
What is the coumadin?
Warfarin
What is the mechanism of action of Warfarin?
Inteferes with normal synthesis and γ carboxylation of vitamin K dependent clotting factors II, VII, IX and X and proteins C and S
Who metabolizes Warfarin?
By cytochrome P 450 pathway
What do laboratory assay stbalish about Warfarin?
Warfain has effect on extrinsic pathway
Which lab study is modified with Warfarin?
↑ PT
How is the half life of Warfarin?
Long half life
Clinical use for Warfarin
Chronic anticoagulation (after STEMI, venous thromboembolism prophylaxis, and prevention of stroke in atrial fibrillation)
What main difference does Warfarin has compared to Heparin?
Warfarin is not used in pregnant women (because warfarin, unlike heparin, can cross the placenta)
How is Warfarin monitored?
Follow PT/ INR values
Toxic effects of Warfarin
Bleeding, teratogenic, skin/ tissue necrosis, drug interactions
What is used fro reversal of warfarin overdose?
Give vitamin K
What is used for rapid reversal of severe warfarin overdose?
Frozen plasma
Direct Factor Xa inhibitors
Apixaban, rivaroxaban
Mechanism of action of Apixaban, rivaroxaban
Bind and Directly inhibit Factor Xa
Which Direct Factor Xa inhibitors is used in Pulmonary embolism?
rivaroxaban
Clinical use for Apixaban, rivaroxaban
Treatment and prophylaxis of DVT, stroke prophylaxis in patient with atrial fibrillation
What is a benefict of Apixaban, rivaroxaban ?
Oral agents do not require coagulation monitorin
Toxic effect of Apixaban, rivaroxaban
Bleeding
Which is the antidote for Direct Factor Xa inhibitors?
No specific reversal agent available
How is the structure of Heparin?
Large anionic, acicid
Route of administering Heparin
Parenteral (IV, SC)
Site of action of Heparin
Blood
Onset of Action of Heparin
Rapid (seconds)
Activates antitrhrombin, which ↓ the action of IIa (thrombin) and factor Xa
Heparin
How is the duration of action of Heparin?
Acute (hours)
Does Heparin inhibits coagulation in vitro?
Yes
Treatment of acute overdose of Heparin
Protamine sulfate
How is Heparin monitored?
By PTT
Which pathway is altered by Heparin?
Intrinsic pathway
Does Heparin crosses placenta?
No
Structure of Warfarin
Small lipid-soluble molecule
Route of administering Warfarin
Oral
Site of action of Warfarin
Liver
Onset of action of Warfarin
Slow, limited by half lives of normal cloting factors
Impairs the synthesis of vitamin K dependent clotting factors
Warfarin
What is the mechanism of action of Warfarin?
Vitamin K antagonist
How is the duration of action of Warfarin?
Chronic (days)
Does Warfarin inhibits coagulation in vitro?
No
Treatment of acute overdose of Warfarin
IV vitamin K and fresh frozen plasma
How is Warfarin therapy monitored?
With PT/INR
Which pathway is modified with Warfarin therapy?
Extrinsic pathway
Does Warfarin crosses placenta?
Yes (teratogenic)
Who are Thrombolytics?
Alteplase (tPA)
Reteplase (rPA)
Tenecteplase (TNK-tPA)
What is tPA?
Tissue plasminogen activator (tPA)
Mechanism of actionof Thrombolytics
Directly or indirectly aid conversion of plasminogen to plasmin, which cleaves thrombin and fibrin clots
How are coagulation times affected by Thrombolytics?
↑ PT
↑ PTT
Do thrombolytics affect platelet count?
No change in platelet count
Clinical use for Thrombolytics
Early MI, early ischemic stroke, direct thrombolysis of severe Pulmonary Embolism
Toxic effect of thrombolytics
Bleeding
Contraindications of Thrombolytic drugs
In patients with active bleeding, hystory of intracranial bleeding, recent surgery, known bleeding diatheses, or severe hypertension
How is thrombolytic toxicity treated?
With Aminocaproic acid
What is aminocaproic acid?
An inhibitor of fibrinolysis
What else can be used to correct factor deficiencies?
Fresh frozen plasma and cryoprecipitate
What is the mechanism of action of aspirin?
Irreversibly inhibits cyclooxygenase (both COX-1 and COX-2) enzyme by covalent acetylation
What is the effect of aspirin on platelets?
Platelets cannot synthesize new enzyme, so effect lasts until new platelets are produced
What efect does aspirin has?
↑ bleeding time, ↓ TXA2 and prostaglandins
How does aspirin affects PT and PTT?
No effect on PT or PTT
Clinical use for Aspirin
Antipyretic, analgesic, anti-inflammatory, antiplatelet (↓ aggregation)
Toxic effects of Aspirin
Gasrtic ulceration, tinnitus (CN VIII)
What does chronic use of aspirin leads to?
Acute renal failure, intesrtitial nephritis, and upper GI bleeding
What is the effect of Aspirin in children?
Reye syndrome when treating Viral infection
What happens with Aspirin overdose?
Causes Respiratory alkalosis initially, which is then superimposed by metabolic acidosis
ADP receptor inhibitors
Clopidogrel, ticlopidine, prasugel, ticagrelor
How is clopidogrel consider?
ADP receptor inhibitor
Mechanism of action of clopidogrel
Inhibit platelet aggreagation by irreversibly blocking ADP receptor
What is the effect of clopidogrel with fibrinoge?
Inhibit fibrinogen binding by preventing glycoprotein IIb/IIIA from binding to fibrinogen
Clinical use for ADP receptor inhibitors
Acute coronary syndrome, coronary stenting
What is a benefit of clopidogrel use?
↓ incidense of recurrence of thrombotic stroke
Toxic effect of toclopidine
Neutropenia
Possible secondary effect of ADP receptor inhibitors
TTP/ HUS may be seen (Thrombocytopenic Purpura (TTP) and Hemolytic-Uremic Syndrome (HUS))
Phosphodiesterase III inhibitor
Cilostazol, dipyridamole
What is the mechanism of action of Cilostazol, dipyridamole?
Phosphodiesterase III inhibitor; ↑ cAMP in platelets, thus inhibiting platelet aggregation; vasodilators
Clinical use for Cilostazol, dipyridamole
Intermitent claudication, coronary vasodilation, prevention of stroke or TIAs (Transient ischaemic attack), angina prophylaxis
Which medicine is combined with Cilostazol, dipyridamole, in Transient ischaemic attack?
Aspirin