Oral Anticoagulants

Question 1

What are the oral anticoagulants?

Answer 1

Warfarin (coumadin), Dabigatran (Pradaxa), Rivaroxaban (Xarelto), Apixaban (Eliquis)

Question 2

Warfarin MOA

Answer 2

Reversibly binds and inhibits enzymes which converts inactive vit K to active vit K, decreases production of vit K-dependent clotting factors; decreases production of natural anticoagulants protein C and S

Question 3

Warfarin (Coumadin) facts

Answer 3

racemic mixture, well absorbed (100%) highly protein bound to albumin, average T1/2: 36-42 hours

Question 4

Warfarin (Coumadin) monitoring

Answer 4

Done with INR, responsive to depression of factors II, VII and X; initial prolongation due to factor VII, antithrombotic effect requires 5-7 days of treatment

Question 5

Challenges associated with warfarin

Answer 5

Drug interactions, frequent monitoring, food interactions, genetic variances in metabolism, narrow therapeutic index, disease state interactions, long/variable half-life, stigmas

Question 6

Factors that increase the effects of warfarin

Answer 6

hyperthyroidism, fever, liver disease, acute heart failure, diarrhea/vominting, genetics

Question 7

Factors that decrease the effects of warfarin

Answer 7

hypothyroidism, fat malabsorption, genetics

Question 8

Drug interactions of warfarin that increases effect

Answer 8

ciprofloxacin, bactrim, alcohol, citalopram, fish oil, propranolol etc

Question 9

Drug interactions of warfarin that decrease effect

Answer 9

griseofulvin, ribavirin, rifampin, mesalamine, barbiturates, high vit K foods

Question 10

Clinical uses of warfarin

Answer 10

prevention of stroke in patients with afib, VTE, history of stroke, VTE prophylaxis

Question 11

Exception to goal 2-3 INR in pt taking warfarin

Answer 11

pt with mechanical valves, goal is slightly higher

Question 12

What is bridge therapy

Answer 12

treating patients with concurrent anticoagulants to bridge the gap between when the warfarin is initiated and when it is therapeutic

Question 13

What is most common drug used with bridge therapy

Answer 13

enoxaparin

Question 14

Pros of early therapeutic INR

Answer 14

decreased length hospital stay, decreased cost of and exposure to using injectable anticoagulants

Question 15

Cons of early therapeutic INR

Answer 15

risk of bleeding, increased hospital stay and cost, clouded picture of patient’s maintenance dose

Question 16

Risk factors for bleeding

Answer 16

patient older than 75 yo, bleeding history, serious comorbid conditions, HTN, CVD

Question 17

When to obtain INR

Answer 17

after 2-3 doses of warfarin and then daily until therapeutic INR reached, outpatient reduce initial monitoring to every few days until a therapeutic dose

Question 18

Initiating warfarin

Answer 18

start 5-10 mg for first 1-2 days, subsequent dosing based on INR response, do not load doses

Question 19

When to start doses lower than 5 mg

Answer 19

in patients with increased risk of bleeding, elderly, debilitated, malnourished, CHF, liver disease

Question 20

Monitor using

Answer 20

INR, PT, PTT

Question 21

what is used to reverse anticoagulation with decreased vitamin K

Answer 21

phytonadione

Question 22

Vitamin K recommendations

Answer 22

INR9 5 mg PO, INR >20 or serious bleeding 10 mg IVPB, if no signs or symptoms of bleeding do not treat

Question 23

Dabigatran (Pradaxa)

Answer 23

Oral direct thrombin inhibitor, must adjust for renal, very fast onset (6hrs) so no bridge needed, no monitoring required, no antidote for bleeding, some DI

Question 24

Clinical uses of dabigatran (Pradaxa)

Answer 24

prevention of stroke and systemic emboli in nonvalvular Afib, treatment of VTE (requires 5-10 days of parenteral anticoagulation

Question 25

Rivaroxaban (Xarelto)

Answer 25

oral factor Xa inhibitor, very fast onset (4 hrs), once daily, no reliable lab monitoring available, no reversal agent, renal adjustment

Question 26

Rivaroxaban (Xarelto) clinical uses

Answer 26

prevention of VTE after hip or knee surgery, treatment of VTE reduction in risk of recurrent VTE, prevent stroke and systemic in nonvalvular Afib

Question 27

Apixaban (Eliquis)

Answer 27

oral factor Xa inhibitor, BID, very complex dosing, very fast onset (3 hrs), renal adjust, no reliable lab monitoring, no reversal agents

Question 28

Apixaban (Eliquis) clinical uses

Answer 28

prevention of VTE post operatively, prevention of stroke and systemic emboli in nonvalvular Afib

Question 29

All NOAC

Answer 29

new, brand only, $$$, all eliminated via kidney, slight differences with efficacy and bleeding