20-Drugs for Coagulation Disorders Flashcards
what is the purpose of a vessel spasm?
constricts vessels and limits blood flow to site on injury
What do activated platelets release? and what do these stimulate?
ADP, thromboxane A2
stimulate activation of new platelets, platelet agg, and vasoconstriction
role of thrombin
converts fibrinogen into fibrin
what does fibrin act as
scaffolding to form a clot
explain the process small vessels undergo after injury (acute)
injury
spasm
platelets adhere to injury site and agg to form plug
formation of insoluble fibrin strands and coagulaiton
the common pathway:
begins when the intrinsic and extrinsic pathways of coagulation converge at the time of factor Xa synthesis
when is fibrinolysis initiates and what enzyme is responsible for this process? (how it is produced?)
initiated 24-48h our clot formation
plasmin digests fibrin and destroys the clot
cells adjacent to the clot release t-PA (tissue plasminogen factor) that converts plasminogen into plasmin
antifibrinolytics:
inhibit clot breakdown
inhibit conversion of plasminogen into plasmin
Thrombolytics Action
dissolve blood clots
increase activation of plasminogen activator to increase conversion of plasminogen into plasmin
thromboembolic disorders lead to
- formation of non-therapeutic clots
- occlusion of arterial vessels leading to MI and/or CVA
- embolus
thrombocytopenia and hemophilia and examples of
- bleeding disorders
thrombocytopenia - low platelet count due to bone marrow suppression
anticoagulant: type of modification, mechanism (general)
- prevention of clot formation
- inhibition of specific clotting factors
anticoagulant/antiplatelet: type of modification, mechanism
- prevention of clot formation
- inhibition of platelet actions
- increase time needed to form a clot
thrombolytic: type of modification, mechanism
removal of existing clot
dissolving clot
antifibrinolytic: type of modification, mechanism
promotion of clot formation
inhibition of destruction of fibrin
what are the most commonly prescribed coagulation modifiers? why?
anticoagulants. work predominantly w venous system
5 “sub-classes” of anticoagulant drugs
heparin warfarin low molecular weight heparins direct thrombin inhibitors direct acting factor Xa inhibitors
antidotes: heparin: warfarin: low molecular weight heparins: direct thrombin inhibitors: direct acting factor Xa inhibitors:
heparin: protamine sulphate
warfarin: vit K
low molecular weight heparins: protamine sulphate
direct thrombin inhibitors: idracizumab (praxibind)
direct acting factor Xa inhibitors: andexanet alfa (Andexxa)
Heparin: mechanism of action, uses, monitoring
- very potent anticoagulant
- catalyzes inactivation of thrombin (enhances antithrombin effects and thrombin no longer converts fibrinogen into fibrin, inhibiting factor Xa and intrinsic pathway)
LMWH (low molecular weight heparin): mechanism of action, uses, monitoring
- anticoagulant that inhibits factor Xa (thrombin is active, more stable response)
- reduced risk of thrombocytopenia
- reduced dose frequency, longer duration of action
- drug class of choice for DVT
- less monitoring, SC by weight
Warfarin: mechanism of action, uses, monitoring
- anticoagulant; blocks synthesis of clotting factors thrombin, VIIa, IXa, Xa (inhibits epoxide reductase which recycles vit k)
Direct acting thrombin inhibitors: mechanism of action, uses, antagonist
- anticoagulant; directly binds and inhibits thrombin (prevents fibrinogen into fibrin)
- reduces risk of stroke, systemic embolism in pt.s w AF, DVT, and pulmonary embolism
- expensive - used in cases of heparin-induced thrombocytopenia
- antagonist: Praxbind (IV)
praxbind (IV): uses
- antagonist for directly acting thrombin inhibitors (anticoagulant), promotes clotting
- used for life-threatening bleeding or uncontrolled bleeding and in emergency surgery or procedures
- dabigatran? binds to praxbind w higher affinity than thrombin
Direct Acting Factor Xa Inhibitors: mechanism of action, uses, antagonist
- highly selective inhibition of factor Xa
(inhibit intrisic and extrinsic pathways and reduce thrombin formation w not direct effects on thrombin or platelets) - used to prevent and treat DVT (pulmonary embolus in pt.s w knee surgery)
- replacing warfarin and some LMWHs
- antagonist: Andnexaet (Andexxa, IV)
Why are Direct acting thrombin and Factor Xa inhibitors beginning to replace warfarin and some LMWHs?
- PO, predictable effects, less monitoring, few (known) drug drug interactions
Andnexaet (Andexxa, IV)
- antagonist for direct acting factor Xa inhibitors
anticoagulant drugs: general cautions, common adverse effects
caution w hemorrhagic disorders, recent trauma, spinal puncture, GI ulcers, recent surgery
- adverse effects: bleeding, INR (internal normalized ration - prothrombin lvls), prothrombin time
Antiplatelet Drugs: 3 types w ex.
- irreversible COX inhibitors: aspirin
- ADP receptor antagonists: Clopidogrel, Ticagrelor
- Glycoprotein IIb/IIIa receptor antagonists (IV only): Abciximab, Tirofiban, Eptifibatide
Antiplatelet Drugs: Cautions and common adverse effects
- presence of known bleeding disorder, recent surgery, closed head injuries
- adverse effect: bleeding, increased bruising, bleeding while brushing teeth
- gastritis, ulcerations
Aspirin: type, mechanism of action, who does it benefit?
antiplatelet: irreversible binding to COX 1 and 2
- inhibits PG synthesis and thromboxane A2
- sig. benefit for pt.s w CVD, controversial for pt.s without CVD (increased bleeding risk)
Why is it beneficial that aspirin can have anticoagulant factors at a lower dose (81mg)?
no association w gastric ulcers
ADP receptor antagonists:
- antiplatelet, irreversibly changes molecular conformation of ADP receptors on platelets
- PO alt. to ASA
- reduction in relative risk of ischemic stroke, MI, or vascular death compared to aspirin
- Ticagrelor - faster onset, greater efficacy
role of ADP and glycoproteins IIb/IIIa in coagulation
recruit platelets to aggregate
Glycoprotein IIb/IIIa inhibitors: class, use
- antiplatelet
- expensive!
- reserved for pt/s w recent MI or stroke undergoing angioplasty (IV)
Thrombolytic Drugs:
- lysis clots, not preventative
- increase the conversion of plasminogen to plasmin to breakup clots
- used for MI, pulmonary embolism, DVT, CVA, and ischemnic stroke
Do platelets bind with high or low affinity to the damaged vessel?
High
What do activated platelets release? And what does that stimualte?
ADP and thromboxane A2
- stimulated new platelets, platelet aggregation and vasoconstriction
What is the function of thrombin?
Converts fibrinogen to fibrin
T/F: Fibrin forms the clot and provides clot robust
true
Extrinsic pathway
- outside vessel
- damaged tissue produce thromboplastin released from damaged cells
- factor Xa produced
Intrinsic Pathway
- inside bv
- collagen is exposed at injury site
- produce Xa
What is produced in both intrinsic and extrinsic pathways and what is its purpose?
Factor Xa; important in converting prothrombin to thrombin so fibrin is made
What is the function of plasminogen activator?
Converts plasminogen to plasmin which dissolves fibrin so clot is broken down
When would you give a drug that enhances plasmin?
- MI
- Stroke
What are the most prescribed coagulation modifiers?
anticoagulants
Which route would you administer an anticoagulant in an emergency? ex of drug
IV or SC; heparin
Which route would you administer in an emergency when stabilized? ex of drug
PO or SC; warfarin
Types of anticoagulants
- heparin
- warfarin
- Low molecular weight heparins
- direct thrombin inhibitors
- direct acting factor Xa inhibitors
How is heparin administered? What is the antidote?
IV, SC; protamine sulphate
How is warfarin administered? and what is the antidote?
PO; Vitamin k
How is low molecular weight heparins administered? and antidote?
SC; protamine sulphate
How are direct thrombin inhibitors administered?antidote?
PO, praxbind
How are direct acting factor Xa inhibitors administered? Antidote?
Po; Andexxa
What drug is known as the natural coagulant and where is it found?
- heparin; is found in liver and lining of bv
What is heparin used to prevent?
- used to prevent DVT, pulmonary embolism, DIC, treat Mi and stroke
- monitor for bleeding (risk of thrombocytopenia)
What should be monitored while using heparin?
Bleeding
What is the drug class of choice to prevent DVT?
Low molecular weight heparins
If one was to be switching meds from heparin to warfarin how long would the drugs be coadministered?
3 days due to increased risk of bleeding and anticoagulants effects lasting 4-5 days
How much of warfarin is bound to plasma proteins?
95-99%
T/F: patients on warfarin should avoid foods high in Vit K
true
T/F: patients should avoid things that could potentially cause injury resulting in blood lose while on warfarin?
true
Direct acting thrombin inhibitors results in
- thrombin not being able to convert fibrinogen into fibrin
- no clot formation
When is praxbind used and what does it do?
- uncontrolled bleeding/life threatening
- case of emergencies
- binds with higher affinity than thrombin and doesnt allow for anticoagulation effects
T/F: Warfarin is contraindicated in pregnancy and during lactation
true
T/F: Heparin is contraindicated in lactation and pregnancy
false; does not cross placental barrier
When should caution be used with anti-platelet drugs?
- presence of any known bleeding disorder
- recent surgery
- closed head injuries
Adverse effects of anti-platelet drugs
- bleeding, bruising
- risk of excessive bleeding with combination of drugs affecting blood clotting
Issues with ASA
- gastritis
- ulcerations
T/F: Thrombolytics dissolve all clots (therapeutic and non therapeutic)
true
Thrombolytic drugs are contraindicated with
- any recent surgerys
- internal bleeding
- monitor for cerebral hemorrhage
Which drug can only be administered once? (thromboylitic) and why?
- streptokinase
- body forms antibodies against this drug