Anticoagulants Flashcards
Warfarin use compared to other anticoagulants
inhibits the synthesis of clotting factors
anticoagulants function
all but warfarin inhibit the activity of clotting factos
where do venous thrombi occur
at sites where blood flow is low - stagnation of blood flow initiates the clotting cascade
Classes an anticoagulants
1) vitamin k antagonist
2) antithrombin activators
3) direct thrombin inhibitors
4) direct Xa inhibitors
Warfarin (coumadin/ jantoven) indications
MI, thromboembolic complications (PE, DVT, afib, CARDIAC VALVE REPLACEMENT)
US box warnings for Warfarin (coumadin/ jantoven)
- bleeding risk
- monitor INR on all treated patients
MOA of Warfarin (coumadin/ jantoven)
Inhibits the synthesis of certain clotting factors
2,7,9,10 and protein c and s via inhibiting vitamin K epoxide reductase complex 1 and decreasing activation of the factors
- essentially a VITAMIN K ANTAGONIST
ADR OF Warfarin (coumadin/ jantoven)
BLEEDING (<5% when INR is 4 or less)
metabolism / excretion of Warfarin (coumadin/ jantoven)
1) adjusting dose in kidney function may need to happen- no robust guidelines - 10/20% reduction in eGFR <60
2) liver function plays a significant role in anticoagulant response - monitor INR closely
routes of Warfarin (coumadin/ jantoven)
oral
- color coordinated!
Warfarin (coumadin/ jantoven) contraindications (7)
1) hemorrhagic tendencies- active GI bleed or ulceration, respiratory or GU tract bleed
2) recent or potential surgery on spine or eyes
3) malignant, uncontrolled HTN
4) pericarditis or pleural effusion
5) bacterial endocarditis
6) patients with high potential for non compliance
7) pregnancy/breast feeding
Regular INR, warfarin normal INR, and warfarin INR for those after cardiac valve replacement
1 = normal
2-3 = regular usage
2.5-3.5 = cardiac valve replacement (for most of them)
- Most patients we will start them in the hospital. Most patients with Warfarin are seen on an every 4 week basis
Vitamin K, Phytonadione Indications
1) hemorrhage prevention in newborns (intracranial) - single dose of injectable phytonadione immediately after delivery supported by AAPA
2) warfarin antidote- reverses hypoprothrombinemia and bleeding (preoperatively or in the case of severe bleeds)
MOA of Vitamin K, Phytonadione
required for synthesis of prothrombin (PT) and clotting factors 7,9,10 (vitamin k dependent factors) and are essential for the coagulation cascade
Route Vitamin K, Phytonadione
oral tablets are expensive
can be IV/Im
ADR Vitamin K, Phytonadione
essentially there is no storage- metabolism and secretion can occur rapidly
how is Vitamin K obtained
in the diet and synthesized by the normal gut flora
food interaction with warfarin
- vitamin k containing foods decrease INR and effects (leafy greens, mayo)
- foods increase the effects- alcohol, cranberries, cherries, and grapefruit
Drug interactions with Warfarin
- interactions can increase effectiveness (more bleeding) or decrease (more clotting)
- in general interactions of long term drugs can be managed by adjusting dosing
- acute use drugs need to be weighed carefully
notable drug interactions with warfarin (3)
1) SULFA-ANTIBIOTICS (most important)- displace warfarin on albumin - significant bleeding risk (bactrim)
2) tylenol- used to be considered safe and NSAIDs/ASA weren’t , now shown to increase INR
3) carbamazepine, phenobarbital and rifampin - powerful induces in CYP stream and DECREASE THE EFFECTS
Warfarin clinical pearls
- in patients with new onset DVT/PE or other active clots, warfarin is started at the same time as parenteral anticoagulate and is continued for a MINIMUM of 5 DAYS AND until the INR is greater or equal to 2 for 24 hours
- CHEST guidelines now recommend apixaban, rivaroxaban, dabigatran or edoaban (NOACS, novel oral anticoagulants) over warfarin for DVT / PE (non cancer) and LMWH over warfarin
heparin (unfractionated heparin ) indications
1) anticoagulation - prophylaxis and treatment of thromboembolic disorders, preventing of clotting in arterial and cardiac sx, anticoagulation for blood tx, extracorporeal circulation and dialysis procedures
heparin (unfractionated heparin) MOA
potentiates the action of antithrombin III- inactivating thrombin and factor Xa- prevents conversion of fibrinogen to fibrin (clot formation )
contraindications of heparin (unfractionated heparin)
severe thrombocytopenia, history of HIT, and uncontrolled active bleeding
Routes heparin (unfractionated heparin)
1) iv (full dose, treatment dose) -algorithim based following anti-Xa or activated partial thromboplastin time (aPTT) levels
- bolus- given if effect is needed immediately
2) subQ
- 5000 mg q8-12
- 7500 mg q12 for obese
ADR heparin (unfractionated heparin)
1) bleeding and thrombocytopenia
2) localized reactions in subQ administration- bruising, irritation, hemotoma
metabolism/ excretion heparin (unfractionated heparin)
onset of action- within MINUTES of IV administration
doses of heparin (unfractionated heparin)
1) IV - full dose based on aPTT
give bolus now and then follow up with a continuous fusion (give to someone with an active clot)
2) subQ (prophylaxis)
5000 units q8-12h or 7500 units q8h in morbidly obese)
Heparin induced thrombocytopenia
- potentially fatal immune mediated disorder- results in rapid platelet count drops and potentially a paradoxical INCREASE in clotting
- antibodies are developed against heparin platelet complexes causing damage to the vascular endothelium - increases clotting and decreasing platelets
heparin induced thrombocytopenia confirmatory test
heparin platelet factor 4 antibody test (PF4 ELISA) and serotonin release assay (SRA)
what do you use when HIT is confirmed/ suspected
argatroban
protamine indications
heparin neutralization