Week 5: Anticoagulants Flashcards
Which is the following is the preferred medication to reverse the anticoagulant effects of unfractionated heparin?
a) Vitamin K
b) Protamine Sulfate
c) Platelet transfusion
d) Plasma components
b- protamine sulfate
The onset of anticoagulation effect of warfarin usually occurs how soon after the initiation of therapy?
a) immediately
b) 1 to 2 days
c) 3 to 5 days
d) 5 to 7 days
c - 3 to 5 days
Compared with unfractionated heparin, characteristics of low-molecular-weight heparin (LMWH) include all of the following except:
a) more antiplatelet effect
b) decreased need for monitor of anticoagulant effect
c) longer half-life
d) superior bioavailability
a - more antiplatelet effect
What is the international normalized ratio (INR) range recommended during warfarin therapy as part of the management of a patient with DVT?
a) 1.5 to 2.0
b) 2.0 to 3.0
c) 2.5 to 3.5
d) 3.0 to 4.0
b - 2.0 to 3.0
Which of the following belongs in the direct thrombin inhibitor class?
a) rivaroxaban
b) dabigatran
c) apixaban
d) edoxaban
b - dabigatran
Clotting Cascade
Warfarin MOA and unique indication that it must be given for
- Vitamin K antagonist - depletes functional Vitamin K reserves by competitively inhibiting VKORC1 complex, which reduces the ability of the liver to synthesize (produce) the Vitamin K dependent clotting factors (X, IX, VII, and II) - [2+7= 9 which is one less than 10]
- mechanical heart valve - Warfarin is the only drug FDA approved for this - need INR to be 2.5 to 3.5 (need this INR level if pt has had a previous clot while taking Warfarin)
What enzymes are involved in the metabolism of Warfarin?
- CYP2C9 and CYP 1A2 - causes a large number of drug interactions - remember that this drug is also 99% protein bound so small changes can lead to changes in blood level of warfarin
Warfarin precautions/ contraindications
- patients with fall risk
- dementia
- uncontrolled HTN
- absolute contraindication: Pregnancy Category X - do not use in pregnancy
- caution in hepatic impairment
- hypermetabolic state (avoid)
- important to stay with the same brand or generic type of coumadin/warfarin
- safest in patients with kidney disease because of frequent monitoring
The effects of Warfarin may be decreased by:
a) Carbamazepine
b) Vitamin K rich foods
c) Oral contraceptives
d) all of the above
D -all of the above
What can you give if the patient taking warfarin has an seriously elevated INR?
give Vitamin K
Warfarin ADRs
- thrombocytopenia - hyperkalemia
Situations when the NP should consider decreasing the initial dose of Warfarin therapy:
- pt is older than 75 years old
- multiple comorbid conditions
- elevated liver enzymes
- changing thyroid status
Heparin MOA
- increases the action of antithrombin III (a naturally occurring antithrombotic agent) thereby inactivating thrombin and inhibiting the activity of numerous coagulating factors
- prevents the conversion of fibrinogen to fibrin
- its effect on thrombus formation is immediate
Heparin cautions/contraindications
- use caution when combining w/ conditions that may predispose to hyperkalemia
- Avoid in pregnancy
- ok with lacation
Heparin ADRs
- hyperkalemia
- thrombocytopenia
- anemia
Drug interactions with Heparin
- 3A4 Inducers
- cephalosporins and PCNs - beta-lactam antibiotics - decreases vitamin K absorption - decreased clotting factors - increased risk of bleeding
- warfarin, antiplatelet meds, thrombolytics
- valproic acid - antiseizure medications - CYP 3A4 inducers
Low Molecular Weight Heparin (LMWH) MOA
- potentiates the activity of antithrombin III and inactivates factors Xa and IIa (prothrombin)
LMWH cautions/contraindications
- avoid with pork, sulfites, or benzyl alcohol allergies - use cautiously in renal impairment, untreated HTN, retinopathy, and severe liver dz.
Dabigatran (Pradaxa) MOA
- Direct thrombin inhibitor (DTI) - thrombin is required to turn fibrinogen into fibrin - prodrug
Pradaxa (Dibigatran) ADRs
- dyspepsia
- gastritis
- hemorrhage
Dibigatran (Pradaxa) caution/ contraindications
- not safe in pregnancy
- black box warning concerning epidural or spinal hematomas with spinal interventions
- black box warning concerning discontinuation and increase of thrombotic events
Antidote: Praxbind (Idarucizumab)
Rivaroxaban (Xarelto), Apixaban (Eliquis), Edoxaban (Savaysa), and Betrixaban (Bevyxxa) MOA
“Xa-ban” drugs - direct factor Xa inhibitors
Rivaroxaban (Xarelto) ADR
back pain, abdominal pain, dyspepsia
Apixaban ADRs
nausea
Edoxaban ADR
Skin rash and GI bleeding
Edoxaban antidote
Andexxa
Rivaroxaban, Apixaban, Edoxaban, and Betrixaban cautions/ contraindications
- black box warning: discontinuation and increase in thrombotic events
- black box warning: epidural and spinal hematomas with spinal interventions
- not recommended in pregnancy or lactation
Anticoagulants vs Antiplatelets
Anticoagulants - affect the clotting cascade - makes the blood less able to create clots and thinning the blood Antiplatelets - makes your platelets less sticky and unable to create clots
