Anticoagulants

Question 1

Heparin

Answer 1

• Binds to antithrombin and increases inactivation of clotting factors, primarily thrombin and factor Xa
• Variable binding to plasma proteins
• aPTT used for monitoring
  »> 1.5-2x normal, 60-80 sec
  »> short half life 1.5 hours (given q8-12 hrs)
• Metabolized in the liver and excreted by the kidneys
• preferred AC in pregnancy
• PCP may see it used postop to prevent VTE or as adjunct in treatment of AMI
  »> not typically long term due to risk of HIT

Question 2

Low Molecular Weight Heparin (LMWH)

Answer 2

Enoxaparin and Dalteparin

• longer duration (qD or q12)
• aPTT not required
• Lower risk of osteopenia
• Lower risk of thrombocytopenia
• Antidote protamine sulfate is effective for heparin only
• May accumulate in renal impairment
• Slightly lower risk of bleeding

Question 3

Warfarin

Answer 3

Vitamin K Inhibitor - decreases production of pro clotting factors II, VII, IX, X

Onset is 24-48 hours

approved indications:

• Thrombosis, PE
• Afib or Prosthetic heart valve
• secondary prevention for MI

no renal dosing necessary

antidote: vitamin K

Question 4

INR monitoring

Answer 4

2-3 usually, at least every four weeks

trophy for at least 10-14 days after hip or knee replacement and up to 35 days for hip

not more effective than aspirin for CV risk

FOR VTE TREATMENT: CONTINUE FOR AT LEAST 3 MONTHS
- Benefit of extended use may not outweigh risk in patients with high bleeding risk

Question 5

Factors to Consider when DOAC selection

Answer 5

Dosing and Adherence

• apixaban and dabigatran are dose BID
• ** edoxaban and rivaroxaban are dosed daily

Admin

• Rivaroxaban dose > 10mg should be taken with food
• Betrixaban should be taken with food
• Other DOACs may be taken without regard to food
• Apixaban and Rivaroxaban and edoxaban may be crushed and diluted for admin
• Dabigatran may not be crushed

Parenteral therapy
- ** Dabigatran and edoxaban require lead in therapy with parenteral agent for treatment of acute VTE

Avoid use of DOAC’s

• ** pregnancy, breastfeeding
• ***** mechanical valve

Question 6

Indications of DOAC’s in PCP

Answer 6

Treatment of VTE

• apixaban or rivaroxaban as you can start immediately
• warfarin, dabigatran, edoxaban require lead in therapy
• Patients with low risk of VTE reoccurrence then can stop after 3 months

AFIB

GI BLEED
- pick apixaban or warfarin for afib patients with GI bleed risk factors

Question 7

ASA for primary prevention

Answer 7

ACC/AHA
- low dose adults 40-70yo
» must be higher risk of CVD but not higher risk of bleeding
- Do not give routinely if > 70yo or increased risk of bleeding

USPSTF

• adults 50-59yo who have >10% of 10yr ASCVD risk and not increased for bleeding
• 60-69yo individualized decision
• < 50 and >70 not enough evidence for recommendation