Podcast
Questions and Answers
Which of the following is the primary mechanism by which factor Xa inhibitors prevent thrombus formation?
Which of the following is the primary mechanism by which factor Xa inhibitors prevent thrombus formation?
A patient with a CrCl of 40 ml/min is prescribed rivaroxaban. What dose adjustment, if any, is typically recommended?
A patient with a CrCl of 40 ml/min is prescribed rivaroxaban. What dose adjustment, if any, is typically recommended?
What is the primary method of monitoring anticoagulation effects of heparin therapy?
What is the primary method of monitoring anticoagulation effects of heparin therapy?
A patient experiences a major bleed while on enoxaparin. Which of the following is the most appropriate immediate reversal agent?
A patient experiences a major bleed while on enoxaparin. Which of the following is the most appropriate immediate reversal agent?
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What is the mechanism of action of antiplatelet drugs?
What is the mechanism of action of antiplatelet drugs?
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A patient is prescribed warfarin. Which dietary advice is MOST appropriate?
A patient is prescribed warfarin. Which dietary advice is MOST appropriate?
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A patient requires anticoagulation during pregnancy. Which anticoagulant is typically the preferred option?
A patient requires anticoagulation during pregnancy. Which anticoagulant is typically the preferred option?
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Why might a patient on anticoagulants be advised to avoid alcohol?
Why might a patient on anticoagulants be advised to avoid alcohol?
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Which of the following is NOT a common risk factor for bleeding when on anticoagulants?
Which of the following is NOT a common risk factor for bleeding when on anticoagulants?
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When is full-dose enoxaparin typically administered?
When is full-dose enoxaparin typically administered?
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Study Notes
Anticoagulants
- Anticoagulants work by interfering with blood clotting factors.
- Current treatments target factors Xa or IIa (thrombin).
- Factor Xa inhibitors (rivaroxaban, apixaban, edoxaban, betrixaban) prevent thrombin formation.
- Direct thrombin inhibitors (dabigatran) directly inhibit thrombin.
- This prevents fibrinogen from converting to fibrin, reducing clot formation.
- Transporter proteins (like P-glycoprotein, or P-gp) affect intracellular/systemic drug levels.
- Renal and hepatic P-gp can impact anticoagulant pharmacokinetics.
- Medication metabolism happens through liver enzymes (cytochrome p450).
- Risk factors for bleeding (e.g., female sex, older age, low weight, kidney dysfunction) are important considerations.
- Newer anticoagulants (DOACs) often require less routine monitoring than older ones.
Antiplatelets
- Antiplatelets make platelets less sticky.
Coagulation and Direct Anticoagulants
- Warfarin's effects are measured using the INR and PT.
- Heparin's effects are monitored via aPTT and anti-Xa levels.
- All patients on anticoagulants/antiplatelets should have routine complete blood counts (CBCs).
Specific Anticoagulants
-
Dabigatran:
- Stroke prophylaxis
- 150 mg twice daily
- Renal adjustment needed.
-
Rivaroxaban:
- Stroke prophylaxis
- 20 mg daily
- Renal adjustment needed.
-
Apixaban:
- Stroke prophylaxis
- 5 mg twice daily
- Renal adjustment needed.
-
Edoxaban:
- Stroke prophylaxis
- 60 mg daily (CrCl 50-95 ml/min)
- Renal adjustment needed.
-
Heparin (Lovenox):
- Commonly used for inpatient DVT prophylaxis..5000 units under the skin every 8 hours (SQ)
- Full dose heparin infusion required for patients with existing clots.
- Indications: DVT, PE, arterial embolism, post-operative venous thrombosis prevention, recurrent thromboembolism, MI, unstable angina, anticoagulation during pregnancy, and extracorporeal circulation.
- Contraindications: IV flushing, sickle cell anemia, increasing platelet count, and use during lactation.
- Commonly used for inpatient DVT prophylaxis..5000 units under the skin every 8 hours (SQ)
-
Enoxaparin:
- Dosage varies by patient weight (30–40 mg SQ daily or BID).
- Full dose (1 mg/kg SQ BID) for patients with normal weight/kidney function.
- 1.5 mg/kg SQ daily for lower weight/kidney function.
Reversal of Anticoagulants
-
Warfarin:
- Reversed with vitamin K (oral, IV, or SQ). Reversal can take days.
- Fresh frozen plasma or Human prothrombin complex concentrate (PCC) can quickly reverse effects.
-
DOACs:
- Human prothrombin complex concentrate (PCC) for temporary reversal.
- Hemodialysis for reversal may take hours.
-
Heparin/Enoxaparin:
- Reversed with protamine sulfate.
- Coagulation factors if active bleeding or during surgery.
Education Points
- Patients should be warned about potential bleeding complications (bruising, pink urine, dark stools, nosebleeds, pallor, fatigue).
- Warfarin effectiveness is impacted by vitamin K intake.
- Leafy greens are high in vitamin K.
- Alcohol, chamomile/green tea, and grapefruit juice are to be avoided with warfarin.
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Description
This quiz covers the mechanisms and concerns related to anticoagulants and antiplatelets, focusing on how they function to prevent blood clotting. Topics include current treatments, risk factors for bleeding, and the role of transporter proteins in drug metabolism. Test your knowledge on both direct anticoagulants and antiplatelet therapies.
