Overview
Warfarin MOA
Decrease vitamin K-dependent clotting factors (II, VII, IX, and X) and active Protein C and S
How much do we want INR to rise each day and how much of an adjustment do we make if we need to change dose?
0.1-0.2 each day initially
10-15% change in weekly dose
Non pharm to prevent bleeding
Protect from injury, brush teeth with soft bristle, electric razor, do not walk barefoot, wear gloves when gardening, trim nails safely, avoid activities where pt may hit head
What is used as a reversal agent for warfarin?
Vitamin K
How many days do we hold warfarin prior to procedure and when do we resume?
5 days
resume 12-24 hours after procedure
What test do we use to monitor and what is the target range?
INR 2-3
How often should INR be checked?
q4-6 weeks
Warfarin induced skin necrosis, purple toe
For INR 4.5-10 without bleeding...
recommend against use of vit K, hold warfarin for 2 days and check INR before resuming
What should be used in the 5 days prior to surgery?
CHEST initial dosing recommendations
Loading dose 10 mg daily for first 2 days in healthy patients
Usually start with 5 mg daily
What diet interactions increase/decrease INR?
Decrease: greens, green tea, tobacco
Increase: grapefruit, cranberry, alcohol
Short: prevent extension of clot, embolization and hemodynamic collapse
Long: prevent recurrent VTE and other complications
For INR >10 without bleeding...
give oral vit K, 2.5-5 mg 1 dose
hold warfarin
Bridging is recommended for pts with high and possibly moderate risk for VTE, what classifies high and moderate? (months)
High: VTE within 3 months
Mod: VTE within past 3-12 months, recurrent VTE
If using a parenteral therapy and bridging to warfarin, what determines when you can stop?
Continue for at least 5 days until INR is in therapeutic range for 2 measurements at least 24 hours apart
Drugs that increase/decrease INR and increase bleed risk
Increase INR: Bactrim, FQ, Amiodarone, metronidazole, azole, corticosteroids
Increase bleeding: NSAIDs, omega-3 FA, garlic, ginger, gingko, SSRIs
Decrease INR: barbiturates, rifampin, carbamazepine, phenytoin, coenzyme Q10, multivitamin
Can we use in pregnancy/breast feeding?
No and yes for breast feeding
For serious bleeding or need rapid reversal...
Give vit K 5-10 mg by slow IV infusion
recheck INR in 12 hours and repeat prn
can also use FFP and VIIa if needed
How long is VTE treated?
1st provoked, 1st and 2nd unprovoked, cancer
1st provoked: 3 months
1st unprovoked: at least 3, usually 6
2nd unprovoked: indefinite (low-mod bleed risk) or 3 months (high risk)
1st VTE and cancer: indefinite
Factors that increase sensitivity to warfarin
Age>75, NPO>3 days, hepatic dysfunction, elevated baseline INR, fever, diarrhea, CHF, hyperthyroidism, malignancy, ESRD, concurrent use of interacting drugs
Disease states that increase INR
Increase: CHF, vomiting and diarrhea, hepatic dysfunction, hyperthroidism
Patient education
Watch for increased bleeding, consult provider before starting any new meds, avoid dangerous activities, avoid dietary interactions, keep vit k intake consistent, do not miss a dose, APAP>NSAIDs, avoid excessive alcohol
What are important points about using vit K? (route, dose, AE)
Avoid subQ or IM due to unpredictable response
Use lowest effective dose to avoid resistance
IV push associated with anaphylactic rxns
Check INR before resuming warfarin
Acute treatment (option 1, 2, and 3) and Chronic (1, 2, 3)
Acute:
1. start parenteral and warfarin
2. start parenteral x5-10 days
3. start rivaroxaban or apixaban
Chronic:
1. 2 INRs 24 hrs apart at least 5 days, D/C parenteral and continue warfarin
2. stop parenteral, start dabigatran or edoxaban
3. continue initial agent