Pharmacology, PKPD, and Genomics of Anticoagulants Flashcards
What are anticoagulants?
Drugs that inhibit at least one step of secondary hemostasis, prolonging the time it takes to form a clot
Prevention of anticoags?
Prevent clots from forming (prophylaxis)
Prophylaxis uses _____ doses
LOW
Treatment of anticoags?
1) Afib
2) VTE
3) Some valvular disease
4) Some hypercoagulable states
Treatment uses ______ doses
FULL
____ anticoagulants significantly ______ a patients risk of bleeding
ALL, INCREASE
Which are the parenteral anticoagulants?
Heparin, LMWH, Fondaparinux, Bivalirudin, Argatroban
Which are the oral anticoagulants?
Warfarin, Apixaban, Rivaroxaban, Edoxaban, Dabigatran
Which drugs are the DOACs?
Apixaban, Rivaroxaban, Edoxaban, Dabigatran
When is Warfarin still indicated?
Afib w/ history of moderate/severe rheumatic mitral stenosis
Mechanical heart valves
Some hypercoagulable states
MOA of heparin?
Potentiates antithrombin (AT) –> decreased transformation form prothrombin –> thrombin
Binding to AT increases heparins catalytic activity to ____ fold
1000
Route heparin
SQ (prophylaxis)
IV (treatment)
Half life heparin
1-2 hours (IV)
Monitoring Heparin: Efficacy
Anti-Xa levels or aPTT (1.5-2.5 x baseline) STANDARD
Monitoring Heparin: Goal
Anti-Xa: 0.3-0.7 units/mL (aPTT will be dependent on lab)
Monitoring Heparin: Safety
Hemoglobin, hematocrit, platelets, BLEEDING!
Heparin is typically used in a _____ setting
Hospital
Heparin is rarely used in outpatient!
Drugs that are LMWH
Enoxaparin (Lovenox)
Dalteparin (Fragmin)
LMWH MOA?
Potentiates antithrombin –> decreases transformation from prothrombin –> thrombin AND
inactivates factor Xa
LMWH Route?
SQ (rarely IV)
Dose LMWH?
1 mg/kg Q12H
Half life LMWH
12 hours
Renal CL requirements LMWH
CrCl < 30mL/min
Body Weight Considerations LMWH
May need to adjust doses with BMI > 40 kg/m2
Monitoring: Efficacy LMWH
Anti-Xa monitoring in obese patients, patients with renal dysfunction, pregnant patients
*Pregnant patients have a different Vd needing to monitor
Monitoring: Safety LMWH
Hemoglobin, hematocrit, platelets, BLEEDING, serum creatinine (bc of renal dose adjustments)
LMWH are commonly used in ______ setting
Hospital
Can be given outpatient
LMWH is a shorter chain fraction of heparin =
less effect on thrombin, increase effect on factor X
Brand name Warfarin
Coumadin
Warfarin MOA
Vitamin K antagonist –> reduction in the hepatic synthesis of factors II, VII, IX, and X as well as protein C and S by blocking carboxylation
Warfarin Route
Oral
Half life Warfarin
20-60 days variable
Body Weight considerations Warfarin?
higher bws may require higher doses, no specific way
Warfarin Drug Interactions: MINOR
CYPs
CYP1A2, CYP2C19, CYP3A4
Warfarin Drug Interactions: MAJOR
CYPs
CYP2C9
Monitoring Warfarin: Efficacy
INR for therapeutic level (usually 2-3)
Lab testing
Monitoring Warfarin: Safety
Hemoglobin, hematocrit, platelets, BLEEDING
Warfarin is ______ in pregnancy
Teratogenic
Warfarin decreases ______ of new clotting factors
SYNTHESIS
(for Warfarin to work, currently active clotting factors need to wash out)
Warfarin also decreases _______ of natural anticoagulants proteins ____ and ______
SYNTHESIS
C, S
Half life of Factor II
60 hours
the LONGEST…. multiple days
Half life of Factor VII
6 hours
Half life of Factor IX
24 hours
Half life of Factor X
40 hours
Half life of Protein C
10 hours
Half life of Protein S
42 hours
What are Warfarin limitations?
Frequent INR Monitoring
Bridging Requirements
Peri-procedural anticoagulation
DDI
Drug-Food interactions
Why do we need to overlap with a parenteral anticoagulant?
Protein C quickly depletes = transient
PROTHROMBOTIC STATE
Factor II takes multiple days to wash out
What is an INR test?
created specifically for Warfarin used an inverse ratio of prothrombin time which determines how long it takes for a clot to form
Made regular at all labs, all places have the same INR goals and numbers
Standard Dosing Warfarin: Initial Dose
5 mg daily for 3 days