Anticoagulation Dosing Flashcards
Heparin: Prophylaxis of VTE:
5,000 units SC q8-12H
Heparin: Treatment of VTE
80 units/kg IV bolus
18 units/kg/hr infusion
Heparin: Treatment of ACS/STEMI
60 units/kg IV bolus
12 units/kg/hr infusion
Heparin antidote
protamine
What direct thrombin inhibitor does not cross-react with HIT antibodies?
Argatroban
When monitoring Heparin, when should aPTT or anti-Xa level be checked?
check 6 hours after initiation and every 6 hours until therapeutic.
-then every 24 hours and with every dose change
aPTT therapeutic range
1.5 - 2.5x control (per specific hospital protocol)
Anti-Xa therapeutic range
0.3 - 0.7 units/mL
Side effects of heparin
-bleeding
-thrombocytopenia
-HIT
-hyperkalemia
1mg of LMWH is equivalent to how many units of anti-Xa activity?
100 units
LMWH: Prophylaxis of VTE
30mg SC Q12H
40 mg SC daily
*CrCl less than 30 —> 30mg SC QD
LMWH: Treatment of VTE and NSTEMI
1 mg/kg SC q12H
1.5mg/kg SC daily (for inpatient VTE treatment)
*CrCL less than 30ml/min: 1 mg/kg SC daily
LMWH: Treatment of STEMI in patients less than 75 years old
30 mg IV bolus + 1mg/kg SC dose
followed by 1mg/kg SC q12h (max 100mg for first two SC doses only)
*CrCl less than 30 ml/min: 30mg IV bolus + 1mg/kg SC dose followed by 1mg/kg SC daily
LMWH: Treatment of STEMI in patients greater than 75 years old
No bolus! Just 0.75 mg/kg SC q12h (no bolus - max 75mg for the first two SC doses only)
*CrCL less than 30 ml/min: 1mg/kg SC daily (no bolus)
For dosing both heparin and LMWH, what body weight should be used?
Total body weight
Antidote of LMWH
protamine
Boxed warning for LMWH
-neuraxial anesthesia (epidural,spinal), or spinal puncture
*risk of hematoma or paralysis
Why is anti-Xa level monitoring required in LMWH?
it is more predictable than heparin. but anti-Xa levels are recommended in pregnant patients.
aPTT IS NOT USED!!!!
What are the components of the 4Ts score to find the probability of HIT?
Thrombocytopenia: drop greater than 50% in platelet count from baseline
Timing: 5 to 10 days after the start of heparin or hours if pt was exposed in the last 3 months
Thrombosis: new or skin lesions that are necrotizing or not
inability to identify another cause or inability to rule out HIT
If a patient has HIT but needs an urgent PCI what should be given?
Bivalirudin
What most platelets recover to in a patient with HIT before starting warfarin?
-do not start warfarin therapy unless platelets recover (>150,000 cells/mm3)
-initiate at 5mg max
-overlap with non-heparin anticoagulant for 5 days until INR in target range for 24 hours
Apixaban: Nonvavlular AF
5mg BID
**If they have 2 of the following: then 2.5mg BID
-80 or older
-body weight 60 kg or less
-SCr 1.5 or greater
Apixaban: treatment of DVT/PE
10 mg BID x 7 days then 5 mg BID
if more than 3 months drop to 2.5mg BID
Eliquis: Prophylaxis for DVT post hip or knee replacement
2.5mg BID for 12 days post knee and 35 days post hip
*first dose 12 to 24 hours after surgery
Does Xarelto need to be taken with food?
Yes, doses of 15mg or greater must be taken with a meal (usually evening meal)
Rivaroxaban: nonvalvular AF
CrCl > 50: 20mg with evening meal
CrCl 15-15: 15mg with evening meal
CrCl <15: avoid use
Rivaroxaban DVT/PE treatment
Initial: 15 mg BID x 21 days then 20 mg daily with food
(if greater than 3 months, go down to 10mg daily)
CrCl <30: avoid use
Rivaroxaban: Prophylaxis for DVT (knee/hip) and VTE in acutely ill
10mg daily x 12 days (knee) and x 35 days (hip), 31 -39 days acutely ill)
*first dose 6-10 hours after surgery
CrCl <30: avoid use
Black box warning specifically for edoxaban?
Reduced efficacy in patients with CrCl greater than 95
Black boxed warning for the DOACS
neuraxial anesthesia (epidural, spinal, spinal puncture) at risk for hematomas and paralysis
-premature discontinuation increases risk of thrombotic events
Edoxaban: Nonvalvular AF
CrCl>95: avoid -black box
CrCl: 51-95: 60mg daily
CrCl: 15-50: 30mg daily
CrCl: <15: avoid
Edoxaban: treatment of DVT/PE
60 mg daily after 5-10 days of IV anticoagulation
*If CrCl: 15-50, body weight less than 60 kgm or taking certain P-gp inhibitors, then 30mg daily
CrCl < 15: avoid
Antidote for DOACS
andexanet alfa (Andexxa) but only for Eliquis and Xarelto!
Major Contraindication to fondaparinux (Arixtra)
severe renal impairment with CrCl less than 30 ml/min
Examples of strong dual CYP3A4 and p-gp inducers
Carbamazepine
phenytoin
rifampin
St. John’s wart
Strong dual inhibitors of CYP3A4 and P-gp
Clarithromycin
itraconazole
ketoconazole
ritonavir
What are eliquis and Xarelto major substrates for?
CYP3A4 and p-gp
Converting from warfarin to another oral anticoagulant
Rivaroxaban when INR is < 3
Edoxaban when INR 2.5 or less
Apixaban when INR is <2
Dabigatran when INR is <2
READ
Converting from a DOAC to warfarin
Stop DOAC
Start parenteral anticoagulant and warfarin at next scheduled dose
Refer to edoxaban package insert for conversion
Converting from dabigatran to warfarin
Start warfarin 1-3 days before stopping dabigatran (determined by renal function)
Dabigatran: Treatment of DVT/PE and reduction of risk of recurrent VTEs
150 mg BID, starting after 5 - 10 days of parenteral anticoagulation
CrCl < 30: avoid
Side effects of dabigatran
-dyspepsia
-gastritis symptoms
-bleeding (including GI)
Antidote of Pradaxa
Antidote = idarucizumab (Praxbind)
Modifiable risk factors of VTE
Acute medical illness
Immobility
Medications (SERMs)
-drugs containing estrogen, erythropoiesis-stimulating agents
obesity (BMI > 30)
pregnancy and postpartum
recent surgery or trauma
Non-modifiable risk factors of VTE
Increasing age
cancer/ chemotherapy
Previous VTE
Inherited/acquired thrombophilia:
AT deficiency, factor V Leiden antiphospholipid syndrome, protein C or S deficiency)
Certain disease states (heart failure, nephrotic syndrome, respiratory failure
Preferred method of VTE treatment in cancer patients
DOACs preferred
What does CHA2DS2-VASC Scoring System stand for and what does each letter represent
Scoring tool for stroke risk
All worth one point unless 2 in name
C- CHF
H- HTN
A2- Age 75 or older
D- Diabetes
S2- Prior stroke/ TIA
V- Vascular disease (MI,PAD, Aortic plaque)
A- Age 65-74
Sc- Sex category of female
Point interpretation of CHA2DS2-VASc score
0-1: Low (no medication required)
1 or more (men): moderate (Consider Med)
2 or more (female)
2 or more (Men)
3 or more (female): oral med recommended (DOACs preferred over warfarin)
What is the HAS-BLED Scoring system and what does it stand for?
-assesses bleeding risk in patient requiring anticoagulation for stroke prevention
-higher the score the greater the risk of bleeding
H- HTN (SBP > 160 mmHg)……..1
A- abnormal liver/kidney function…….1-2
S- Prior Stroke………………..1
B-Bleeding predisposition……………1
L- Labile INR on warfarin………..1
E- Elderly (over 65) ………………….1
D- Drugs (ASA, NSAIDs), alcohol use….1-2
