In a patient with polycythemia vera who is starting hydroxyurea and is taking apixaban 2.5 mg twice daily and amiodarone, should low‑dose aspirin be added?

Yes, add low-dose aspirin despite the apixaban and amiodarone

Low-dose aspirin (81 mg once or twice daily) should be added to this patient's regimen, as it is a cornerstone of polycythemia vera therapy and provides distinct anti-thrombotic benefits beyond anticoagulation alone. 1

Rationale for Aspirin in PV

The evidence strongly supports aspirin use in PV regardless of other anticoagulation:

• Aspirin is a Class I, Level A recommendation for all PV patients without contraindications 1
• The ECLAP trial demonstrated that low-dose aspirin significantly reduces cardiovascular death, myocardial infarction, stroke, and major venous thromboembolism in PV patients 1, 2
• Aspirin specifically targets platelet cyclooxygenase-mediated thrombosis, which is a distinct mechanism from the coagulation cascade that apixaban inhibits 3, 4, 5
• PV patients have unique microcirculatory disturbances (erythromelalgia, visual symptoms) that are highly responsive to aspirin but not to anticoagulation alone 6

Addressing the Apixaban Concern

While the apixaban label warns that concomitant aspirin increases bleeding risk 7, this must be balanced against thrombotic risk in PV:

• The patient is already on apixaban 2.5 mg BID (the reduced dose, likely for atrial fibrillation given the amiodarone)
• PV patients have a 16% rate of arterial thrombosis and 7% venous thrombosis at or before diagnosis 3
• The ECLAP trial showed aspirin increased bleeding risk only minimally in PV patients, with a favorable benefit-to-risk profile 2
• Aspirin addresses arterial/platelet-mediated thrombosis while apixaban addresses venous/coagulation-mediated thrombosis—both mechanisms are relevant in PV 4, 5

Drug Interaction Considerations

Amiodarone may increase apixaban levels (Ctrough increased by approximately 50% in one study) 8, which theoretically increases bleeding risk. However:

• The 2.5 mg BID dose is already the lowest therapeutic dose
• Careful monitoring for bleeding is warranted but does not contraindicate aspirin
• The combination is "generally well tolerated" per available data 8

Practical Recommendations

Start with aspirin 81 mg once daily and monitor closely for bleeding:

• Consider twice-daily dosing (81 mg BID) if the patient has particularly high thrombotic risk (age >60, prior thrombosis, high JAK2 allele burden) 4, 5, 9
• Monitor for bleeding symptoms at each visit
• Ensure hematocrit is maintained <45% with hydroxyurea and phlebotomy as needed 3, 5
• Do not reduce or stop aspirin based solely on the presence of apixaban—the mechanisms are complementary

Key Caveats

Contraindications to aspirin that would change this recommendation:

• Active bleeding or recent major hemorrhage
• Extreme thrombocytosis (platelets ≥1000 × 10⁹/L) with acquired von Willebrand disease 3
• History of aspirin-related severe bleeding
• Documented aspirin allergy

If bleeding occurs, consider reducing aspirin to every-other-day dosing or checking serum thromboxane B2 levels to guide precision dosing, as one-third of PV patients show incomplete platelet inhibition on standard dosing 9.