Anticoagulants Flashcards
warfarin MOA
Inhibits synthesis of vitamin K–dependent clotting factors X, IX, VII, and II (prothrombin)
Direct Oral Anticoagulants (DOACs) [formerNovel Oral Anticoagulants (NOACs)] MOA
Factor Xa inhibitor: ◦ Rivaroxaban (Xarelto) ◦ Apixaban (Eliquis) ◦ Endoxaban (Savaysa) ◦ Betrixaban (Bevyxxa)
Direct Thrombin Inhibitor examples
◦ Dabigatran Etexilate (Pradaxa)
◦ Parenteral available also: bivalirudin (Angiomax), argatroban (Argatra, Novastatin, Arganova, Exembol), desirudin (Iprivask, Revasc)
Heparin MOA
◦ Binds with antithrombin III
◦ Inactivates factors IXa, Xa, XIIa, XIII
LMWH MOA
Low-molecular-weight heparin (LMWH)
◦ Regular heparin is processed into smaller molecules
◦ Enoxaparin (Lovenox), dalteparin (Fragmin), fondaparibnux (Arixtra), tinzaparin (Innohep)
◦ Inactivates factor Xa
Fondaparinux (Arixta) MOA
◦ Selective inhibitor of antithrombin III and factor Xa inhibitor
Benefit of LMWH
less monitoring
Warfarin pharmacokinetics
◦ Well absorbed when taken orally
◦ Metabolized by CYP1A2 and 2C9
◦ Half-life of 3 to 4 days*
◦ Duration of effect 2-5 days
Warfarin precautions and contraindications
◦ Pregnancy category X
◦ Use cautiously in patients with fall risk, dementia, or uncontrolled hypertension
◦ Avoid in hypermetabolic state
◦ Do not use as only anticoagulant if patient has documented protein C or S deficiency
Warfarin will not
take effect right away. you will also have t to wait a while to see effects from a dose change
There are a lot of ___ ___ with warfarin
drug interactions
Protien C or S is
active within the clotting cascade. If you take with warfarin it may make clotting worse or cause skin necrosis
Warfarin 2nd line for
VTE
Warfarin treatment for
DVT and PE
Warfarin dose to maintain
INR between 2 and 3
Increase warfarin dose in
small increments (5-20% of total weekly doses)
Warfarin Monitoring
◦ INR daily until in therapeutic range for 2 consecutive days, Then two or three times weekly for 1 - 2
weeks
◦ Then less frequently but at least every 6 weeks
Warfarin ADR
Adverse drug reactions (ADRs)
◦ Bleeding
◦ Allergic reactions
Warfarin atnidote
◦ Antidote is vitamin K
Warfarin common drug interacions
◦ Many drug–drug interactions
◦ Drug-Herbal interactions: Ginseng, Ginko
◦ Drug-Food interactions: Cranberry, grapefruit, greens
◦ Antiplatelet drugs: NSAIDs, ASA
◦ Thrombolytic drugs
Orthopedic surgery (total hip, knee replacement, hip fracture) Trauma surgery - INR Range
INR 1.8-2.2
VTE, a-fib, valvular heart disease, tissue valves
A-fib: CHA2dS2VASc score - INR Range
INR 2.0 – 3.0
Mechanical, prosthetic heart valve replacement - INR Range
INR 2.5 – 3.5*
Greens are rich in
Vit K
Thrombophilia, thromboembolic event (Factor V Leiden,
antiphospholipid syndrome, Protein C, S or Antithrombin
deficiency) - INR Range
2 to 3
Critical Value for INR
5.5
Endogenous factors that will lead to decrease in INR
Edema Coumadin resistance Hyperlipidemia Hypothyroidism Nephrotic syndrome
Exogenous facotrs that willd ecrease INR
Diet hi in Vit K Drug interactions Travel Unreliable INR
other risk factors for decrease in INR
Malabsorption
Medication
dosing error
Pt compliance
alcohol abuse will increase risk for
major bleeding while taking anticoagulants
Actions to take if elevated INR depends on
◦ Clinical severity of bleeding, rate of hemorrhage, and the location
◦ Extent to which INR is elevated
◦ Expected duration of therapy
◦ Initial indication for therapy
Consider this when you have an elevated IRN
◦ Dietary changes
◦ Other medications, drugs, herbals
◦ Dose
Treatment for: INR>therapeutic but <5, no evidence of bleed,
rapid reversal for reasons of surgical intervention
not indicated
Lower dose or omit next 1-2 doses of warfarin and then
resume at lower dose when INR approaches therapeutic
range. Daily INRs
Treatment for: INR>5, <10 and pt is not bleeding (2 options for
treatment)
- Omit next 1-2 doses, monitor INR and resume at
lower dose when INR in therapeutic range. Daily INRs - If pt at increased risk for bleeding, omit next dose and
administer vitamin K 1-2.5mg orally
If more rapid reversal required (e.g. surgery)
Vitamin K 3-5mg(o). Give 1-2mg(o) in 24h if still elevated
Treatment for INR >10 and pt is not pleeding
Hold warfarin. Vitamin K 3-5mg (o). This should reduce INR in 24-48 hours. Recheck INR, if still elevated, may repeat Vitamin K
Serious bleeding: Vitamin K 10mg IV; FFP; Prothrombin complex concentrate (PCC)
Generic warfarin vs. coumadin - consideration
◦ Avoid alternating
◦ Monitor INR more frequently if changing
dental procedures with coumadin
◦ Cessation of coumadin for surgical and nonsurgical dental procedures may pose greater risk of thrombotic events than
hemorrhagic events
Consider lower coumadin dose if:
◦ Older than 65-75 years ◦ Multiple comorbid conditions ◦ Poor nutrition ◦ Elevated liver enzymes ◦ Changing thyroid status ◦ Elevated INR when off warfarin
Surgeon/dentist should be notified of
coumadin therapy prior to procedure
Consider these questions regarding surgery
◦ Based on procedure, what is risk of bleeding associated with anticoagulation?
◦ If anticoagulation therapy is temporarily stopped, what is the risk of thromboembolism?
◦ Is the thromboembolic risk of stopping warfarin sufficient to warrant cross-coverage with UH or LMWH?
