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Flashcards in Anticoagulation Deck (24):
1

Normal hemostasis steps

  1. small blood vessel injury 
  2. vasospasm decreases blood flow
  3. platelets adhere and form a plug to stop bleeding
  4. coagulation activation-->fibrin clot
  5. after vessel is repaired, clot removed by fibronolysis 

2

Virchow's Triad

venous stasis 

hypercoagulobility 

vascular injury 

3

Parenteral anticoagulants

unfractionated heparin (UFH/Heparin)

low molecular weight heparins (LMWH)

4

Mechanism of action of heparin

prevents the conversion of fibrinogen to fibrin, preventing further clotting

does not affect established thrombus 

5

Indications of heparin

venous thromboembolism (DVT/PE) tx and prophylaxis 

unstable angina

acute MI 

coronary bypass surgery 

hemodialysis 

angioplasty

IV line flushes 

6

Pharmacokinetics of heparin

Non-linear elimination of heparin: be careful with dosing because half life increases as dose increases

7

Adverse reactions of heparin 

Hemorrhage 

Heparin induced thrombocytopenia (HIT): platelets <100,000, need to discontinue heparin

Heparin associated thrombocytopenia (HAT): mild thrombocytopenia, manage by observation 

Long term: osteoporosis and hyperkalemia 

8

Antidote for heparin

protamine 

9

Adverse Reactions

Hemorrhage 

Thrombocytopenia and osteoporosis, but less than heparin 

10

Types of oral anticoagulants 

Warfarin 

Dabigatran 

Rivaroxaban 

Apixaban 

(Warfarin only one with antidote)

11

Mechanism of action of warfarin 

Interferes with hepatic synthesis of vitamin K dependent clotting factors (Vit K antagonist)

Onset of effect 36-72 hours

Not thrombolytic

12

Indications to use warfarin

Venous thromboembolis (DVT/PE) treatment and prophylaxis 

Prosthetic heart valves

A fib 

TIA/Stroke

Acute MI 

Hypercoagulable states

Peripheral arterial occlusive disease 

13

Pharmacokinetics of warfarin

(Absorption, distribution, metabolism)

Absorption: Well absorbed in GI tract 99%

Distribution: >97% bound to plasma proteins, crosses placenta, but not breast milk 

Metabolism: Half life is 1-2 days, longer in elderly with CHF exacerbation

14

Adverse reactions of warfarin

Hemorrhage 

Skin necrosis (rare, discontinue drug and administer vitamin K)

Purple toe syndrome

15

CI and precautions of warfarin

Patients with addition risks of hemorrhage

Noncompliance with drug therapy or monitoring 

Alcoholism 

Surgery, dental work 

Spinal anesthesia or injectons

16

Warfarin drug interactions

*Assume an interaction until proven otherwise! 

metabolized by CYP450

Increase INR: sulfamethoxazole (Septra)

Increase bleeding risk, but don't change INR: Aspirin and NSAIDs

17

Dietary considerations for warfarin 

(food)

Make sure that vitamin K intake is consistent to stablize INR

Many supplements can affect platelet function and anticoagulation status--check

18

Alcohol effects on Warfarin

Acute intake: increase INR

Chronic intake: decrease INR (inc hepatic metabolism)

Cirrhosis: increase INR (can't metabolize)

19

Anticoagulation recommendations for prevention of VTE 

Vary depending on risk for VTE 

  • Heparin
  • LMWH
  • Fondaparinux
  • Graduated compression stockings and/or intermittent pneumatic compression devices 

 

20

Anticoagulation recommendations for treatment of VTE

Parenteral anticoagulant and warfarin 

  • Parenteral anticoagulant for 5-7 days (continuous infusion heparin OR subQ UFH, LMWH, or Fondaparinux)
  • Warfarin therapy begins on day 1 after first dose of parenteral anticoagulant 
  • Overlap because heparin has long half life
  • Must have therapeutic INR for 2 days before stopping heparin 

Thrombolytics 

  • Not recommended for most patients because intracranial bleeding can occur

21

CHADS2

Congestive heart failure 

Hypertension 

Age >75yrs

DM

Stroke or TIA

22

Study of variability in hereditary factors as it relates to drug response in different populations

Pharmacogenetics definition

"Right Medicine for the Right Patient"

23

Warfarin Therapy and CYP2C9

CYP2C9 variants are associated with a different warfarin maintenanace dose, time to stable dose, above range INRs and bleeding events

Screening for CYP2C9 may help prescribers avoid overanticoagulating 

24

Contraindications for Anticoagulation Therapy

Active bleeding

Hemophilia

Severe liver disease 

Severe thrombocytopenia 

Malignant HTN

Inability to meticulously supervise and monitor treatment