Hematology Drugs Flashcards
Heparin - mechanism of action
Activator of antithrombin (decrease thrombin and 10a)
Short half life
Heparin clinical use
Immediate anticoagulation for: 1. PE 2. Acute coronary syndrome
3. MI 4. DVT
Heparin - pregnancy
Used during pregnancy - do not cross placenta
Follow heparin by
PTT
Heparin toxicity
- Bleeding
- Thrombocytopenia HIT
- Osteoporosis
- Drug-drug interactions
Heparin antidote (for rapid reversal) and mechanism of action
Protamine sulfate - + charged molecule that binds the - charged heparin
Heparin - induced thrombocytopenia (HIT)
Development of igG against heparin bounded to platelet factor (PF4). That complex activate platelets
HIT symptoms
- Thrombosis
2. Thrombocytopenia
Low molecular weight heparin (examples)
-PARIN
Enoxaparin
Dalteparin
Low molecular weight heparina and fondaparunix (vs heparin)
- Act more on X
- Better bioavailability
- 2-4 h longer half time
- Can be administrated subcuntaneously
- No lab monitoring
- Not easily reversible
Direct thrombin inhibitors
- Argatroban
- Bivalirudin
- Dabigatran
Bivalirudin is related to
Hirudin: the anticoagulant used by leeches
Direct thrombin inhibitors are alternatives to heparin in
HIT
Warfarin duration of life
Long half life
Warfarin mechanism of action
Interferes γ-carboxylation of vit K depended clotting factors 2,7, 9, 10, C, S
In lab assays, warfarin has effect on ….. pathway
Extrinsic
Increased PT
Follow warfarin by
PT/INR
Warfarin clinical use
Chronic anticoagulation:
- Venous thromboembolism prophylaxis
- Prevention of stroke in atrial fibrillation
Warfarin in pregnancy
No - it crosses placenta
Warfarin toxicity
- Bleeding
- Teratogenic
- Skin-tissue necrosis (small vessel microthromboses)
- Drug-drug interactions
Cause of transient hypercoagulability with warfarin use
Pr C and S have shorter half-lives than 2,7,9,10 –> skin tissue necrosis within 1st days of large doses
For reversal and rapid reversal of warfarin
Reversal: vit K
Rapid reversal: fresh frozen plasma
Heparin bridging?
Heparin frequently used when starting anticoagulation. Heparin enables anticoagulation during the initial transient hypercoagulable state by warfarin. Initial heparin reduces the risk of: 1. skin tissue necrosis. 2. Recurrent venous thrombosis
Warfarin action and dose is affected by
Polymorphism in the gene for vit K epoxide reductase complex (VKORC1)
Heparin vs warfarin
Pregnancy
Heparin +
Warfarin - (teratogenic)
Heparin vs warfarin
Monitoring
Heparin PTT
warfarin PT/INR
Heparin vs warfarin reversal
Heparin: protamine sulfate
Warfarin: vit K, fresh frozen plasma
Heparin vs warfarin
Inhibits coagulation in vitro
Heparin +
Warfarin -
Heparin vs warfarin
Duration of action
Heparin: acute (hours)
Warfarin: chronic (days)
Heparin vs warfarin
Onset of action
Heparin: rapid (sec)
Warfarin: slow (limited by half-lives of normal clotting factors)
Heparin vs warfarin
Site of action
Heparin: blood
Warfarin: liver
Heparin vs warfarin
Route of administration
Warfarin: oral
Heparin: parenteral (IV, subcutaneous)
Heparin vs warfarin
Structure
Heparin: large, anionic, acidic polymer
Warfarin: small amphipathic molecule
Heparin mechanism of action
Activator of antithrombin (decrease thrombin and 10a)
Direct factor Xa inhibitors
- Apixaban
2. Rivaroxaban
Direct factor Xa inhibitors (apixaban, rivaroxaban) toxicity
Reversal agent
Bleeding
No reversal agent
Direct factor Xa inhibitors (apixaban, rivaroxaban) mechanism of action
Bind to and directly inhibit factor Xa
Direct factor Xa inhibitors (apixaban, rivaroxaban) monitoring
Oral agents do not need monitoring
Direct factor Xa inhibitors (apixaban, rivaroxaban) clinical use
Treatment and prophylaxis of 1. DVT 2. PE (rivaroxaban)
Stroke prophylaxis in atrial fibrillation
Eculizumab mechanism of action and clinical use
Terminal complement inhibitor
Paroxismal noctural hemoglobinuria
Iron poisoning treatment
- Chelation (iv deferoxamine, oral deferasirox)
2. Dialysis
Thrombolytics
Alteplase (tPA) , reteplase (rPA), streptokinase, tenecteplase (TNK-tPA)
Thrombolytics - mechanism of action
Directly or indirectly aim conversion of plasminogen to plasmin which cleaves thrombin and fibrin clots
Thrombolytics
PT, PTT, PC
PT increased
PTT increased
PC normal
Thrombolytics: clinical use
- Early MI
- Early ischemic stroke
- Direct thrombolysis of severe PE
Thrombolytics toxicity
Bleeding
Thrombolytics antidote
- Aminocaproic acid (inhibits fibrinolysis)
2. Fresh plasma and cryoprecipitate (to correct factor deficiencies)
Thrombolytics is contraindicated
- Active bleeding
- History of intracranial bleeding
- Recent surgery
- Known bleeding diathesis
- Severe hypertension
Aspirin mechanism of action
Irreversible inhibits cycloxygenase (both cox 1 and 2) BY COVALENT ACETYLATION. Platelets cannot synthesize new enzyme, so effect lasts until new platelets produced
Aspirin decreased the production of
- Prostaglandins
2. TXA2
Aspirin - BT PT PTT
No effect on PT PTT
Increased BT
Aspirin clinical use
- Antipyretic
- Analgesic
- Anti-inflammatory
- Antiplatelet (anti-aggregation)
Aspirin toxicity
- Gastric ulceration
- Tinnitus (CN 8)
- Chronic use –> a. Acute renal failure b. Interstitial nephritis c. Upper gi bleeding
- Reye syndrome in children with viral infection
- Overdose –> initially hyperventilation and respiratory alkalosis, but transition to mixed metabolic acidosis-resp alkalosis
ADP inhibitors
- Clopidogrel
- Ticlopidine
- Prasurgel
- Ticagrelor (reversible)
ADP inhibitors mechanism of action
Irreversible blocking ADP receptor (prevent expression of gpIIb/IIIa) (except ticagrelor –> reversible)
Reversible ADP inhibitor
Ticagrelor
ADP inhibitors side effects
- Neutropenia (ticlopidine)
2. TTP may be seen
ADP inhibitors clinical use
- Acute coronary syndrome
- Coronary stent (decreases incidence or recurrence of thrombotic stroke)
- decrease incidence or reccurence of thrombotic stroke
GPII/IIIa inhibitors
- Abciximab
- Eptifibatide
- Tirofiban
GPII/IIIa inhibitors toxicity
- Bleeding
2. Thrombocytopenia
GPII/IIIa inhibitors clinical use
- Unstable angina
2. Percutaenous transluminal angioplasty
Aciximab is made from
Monoclonal antibody Fab fragments
Alternative of heparin in HIT
Direct thrombin inhibitor
Phosphodiesterase III inhibitors
- Cilostazol
2. Dipyridamole
Cilostazole, dipyridamol, mechanism of action
Phosphodiesterase III inhibitor–> increased cAMP in platelets –> inhibitions of platelet aggregation…….and vasodilation
Cilostazol, dipyridamol toxicity
- Nausea
- Headache
- Facial flashing
- Hypotension
- Abdominal pain
Cilostazol dipyridamole clinical use
- Intermittent claudication
- Coronary vasodilation
- Angina prophylaxis
- Prevention of stroke or Transient ischemic attacks (combined with aspirin)
Bivalirudin - mechanism of action
directly inhibits activity of free and clot-associated thrombin
Bivalirudin - clinical use
- Venous thrombooembolism
- atrial fibrilation
(can used in HIT)
Bivalirudin - lab monitoring
does not require
Bivalirudin - side effects
bleeding
Bivalirudin - antidote
- no specific reversal agent
- can attempt to use activated prothrombin complex concentrates (PCC) and/or fibrinolytics (tranxamic acid)