Anticoagulants Flashcards
Heparin MOA
potentiates anti thrombin
decreases pro thrombin –> thrombin
Heparin Route
SQ or IV
Heparin Renal Adjustments
None
Heparin Body Weight considerations
higher body weights may require higher dosing
Heparin Drug Interactions
Additive drugs can cause bleeding
Heparin Monitoring
anti Xa levels or aPTT
hemoglobin, hematocrit, platelets
Heparin Goal
anti Xa level 0.3-0.7 units/ml
LMWH aka…
Enoxaparin
LMWH MOA
potentiates antithrombin
inactivates factor Xa
(decreases pro thrombin –> thrombin)
LMWH Route
SQ or IV (rarely)
Heparin Half Life
1-2 hours
LMWH Half Life
12 hours
LMWH Renal Adjustments
CrCl <30 ml/min
LMWH Body Weight Considerations
BMI ≥ 40 kg/m2
LMWH Drug Interactions
Avoid additive increased bleeding risk
LMWH Monitoring
hemoglobin, hematocrit, platelets
serum creatinine
Anti Xa monitoring in obese, renal dysfunction, or pregnant patients
What class of medication is warfarin?
Vitamin K Inhibition
Warfarin MOA
Vitamin K Inhibition leading to a reduction in the hepatic synthesis of factors
II, VII, IX, X
and protein C/S by blocking carboxylation
Why does warfarin take effect at steady state?
Warfarin inhibits coagulation but also inhibits natural anti coagulation
At SS inhibiting coagulation is greater
Warfarin Route
20-60 hours
Warfarin Renal Adjustments
none
Warfarin Body Weight Considerations
higher body weights may require higher doses
Warfarin Common DDI
Amiodarone Macrolides -azoles Sulfa ABX Rifampin
Warfarin CYP
2C9 major
3A4 minor
Warfarin Monitoring
INR 2-3
hemoglobin, hematocrit, platelets
Warfarin Limitations (5)
- Frequent INR monitoring
- Bridging requirements
- Peri-procedural anticoagulation
- Drug-drug interactions
- Drug food interactions
Initial warfarin dose for patient starting on warfarin
5 mg daily for 3 days
Initial warfarin dose for patient starting on warfarin (more sensitive)
2.5 mg daily for 3 days
What makes a patient more sensitive to warfarin?
frail, elderly, undernourished
liver disease, kidney disease, HF
acute illness
on medication that decreases warfarin metabolism
When do you check the INR on patient starting warfarin?
Day 4
Goal of INR after 4 days after initiation
1.5 - 1.9
Continue starting dosing
Patient starting on warfarin
On day 4 INR is < 1.5
What dose do you give them?
7.5 to 10 mg daily for 2-3 days
Patient starting on warfarin
On day 4 INR is 2-3
What dose do you give them?
2.5 mg daily for 2-3 days
Patient starting on warfarin
On day 4 INR is 3.1 - 4
What dose do you give them?
1.25 mg daily for 2-3 days
Patient starting on warfarin
On day 4 INR is > 4
What dose do you give them?
Hold until INR < 3
Sensitive Patient starting on warfarin
On day 4 INR is < 1.5
What dose do you give them?
5 - 7.5 mg daily for 2 - 3 days
Sensitive Patient starting on warfarin
On day 4 INR is 1.5 - 1.9
What dose do you give them?
Continue starting dose
2.5 mg daily for 2-3 days
Patient starting on warfarin
On day 4 INR is 1.5 - 1.9
What dose do you give them?
Continue starting dose
5 mg daily for 2-3 days
Sensitive Patient starting on warfarin
On day 4 INR is 2 - 3
What dose do you give them?
1.25 mg daily for 2 - 3 days
Sensitive Patient starting on warfarin
On day 4 INR is 3.1 - 4
What dose do you give them?
0.5 mg daily for 2 - 3 days
Sensitive Patient starting on warfarin
On day 4 INR is >4
What dose do you give them?
Hold until INR < 3
Patient already on warfarin
INR <1.5
Increase weekly maintenance dose by 10-20%
Consider one time 1.5-2 times the daily dose
Patient already on warfarin
INR 1.5 - 1.7
Increase weekly maintenance dose by 5-15%
Consider one time 1.5-2 times the daily dose
Patient already on warfarin
INR 1.8 - 1.9
No adjust if last 2 INRs in range
If need:
Increase weekly maintenance dose by 5-10%
Consider one time 1.5-2 times the daily dose
Patient on warfarin
Taking ABX temporarily
What dosing do you do?
On time supplemental 1.5-2 times daily dose
Resume maintenance dose
Patient already on warfarin
INR 3.1 - 3.2
No adjust if last 2 INRs in range
If need:
Decrease weekly maintenance dose by 5-10%
Patient already on warfarin
INR 3.3 - 3.4
Decrease weekly maintenance dose by 5-10%
Patient already on warfarin
INR 3.5 - 3.9
Consider holding 1 dose
Decrease weekly maintenance dose by 5-10%
Patient already on warfarin
INR ≥4 but ≤10 and no bleeding
Hold until INR below 3
Decrease weekly maintenance dose by 5-20%
If patient considered to be a bleeding risk consider oral K
Patient already on warfarin
INR >10 and no bleeding
Hold until INR below 3
Give vitamin K orally
Decrease weekly maintenance dose by 5-20%
Factor Xa Inhibitors
Rivaroxaban Apixaban Edoxaban Betrixaban Fonndaparinux
Apixaban brand name
Eliquis
Apixaban route
oral
Apixaban A fib dose
5mg BID
Apixaban VTE dose
10 mg BID x 1 wek
then 5 mg BID
Apixaban half life
12 hours
Apixaban renal adjustment
A fib Only
2.5mg BID if 2/3 are met:
SCr>1.5
Weight<60
Age>80
Apixaban body weight considerations
Okay in those >120 kg or BMI ≥ 40
Apixaban drug interactions
Major CYP3A4 substrate
Apixaban monitoring
hemoglobin, hematocrit, platelets, serum creatinine
Apixaban Pearls
Best DOAC in patients with poor renal function
DOACs
Apixaban Rivaroxaban Edoxaban Betrixaban Dabigatran
Patient already on warfarin
INR 3.5
Taking drug that temporarily dec. warfarin
What do you do?
One time held dose
Consider resumption of prior maintenance dose