What is the recommended treatment approach for a patient with COVID-19 who is currently on anticoagulant (blood thinner) medication?

COVID-19 Treatment in Patients on Anticoagulation

If a patient with COVID-19 is already on therapeutic anticoagulation for a pre-existing indication (such as atrial fibrillation, prior VTE, or mechanical valve), continue their home anticoagulant regimen throughout their COVID-19 illness unless significant bleeding or other contraindications develop. 1

Outpatient Management

For outpatients with COVID-19 on chronic anticoagulation:

• Continue the patient's existing therapeutic anticoagulation without modification 1
• Do not add prophylactic anticoagulation on top of therapeutic anticoagulation 1
• Monitor for bleeding complications and drug interactions, particularly if COVID-19 antiviral therapies are prescribed 1
• Avoid Paxlovid (nirmatrelvir/ritonavir) in patients on direct oral anticoagulants (DOACs) due to significant CYP3A4 interactions that can dramatically increase bleeding risk 1
• Consider remdesivir or molnupiravir as alternative COVID-19 treatments if antivirals are indicated, as these have minimal drug interactions with anticoagulants 2

Hospitalized Non-ICU Patients

For hospitalized (non-critically ill) patients with COVID-19 on chronic anticoagulation:

• Continue therapeutic anticoagulation for the underlying indication 1
• Switch DOACs to low-molecular-weight heparin (LMWH) or unfractionated heparin (UFH) upon admission due to risk of rapid clinical deterioration, drug-drug interactions with COVID-19 therapies, and unpredictable absorption in acute illness 1
• Prefer LMWH over UFH to limit healthcare worker exposure 1
• Do not escalate to higher anticoagulation doses beyond what is indicated for the underlying condition 1, 3

Special Considerations for Specific Conditions

Atrial fibrillation:

• For new-onset AF in hospitalized COVID-19 patients, initiate therapeutic-dose parenteral anticoagulation regardless of CHA₂DS₂-VASc score 1
• Plan for long-term oral anticoagulation if CHA₂DS₂-VASc ≥1 in males or ≥2 in females 1

Recent acute coronary syndrome (ACS) or percutaneous coronary intervention (PCI):

• Continue dual antiplatelet therapy (DAPT) if on prophylactic-dose anticoagulation for COVID-19 1
• If on therapeutic anticoagulation plus DAPT, individualize the decision to continue or discontinue one antiplatelet agent based on bleeding versus ischemic risk 1

Prior stroke or TIA:

• Continue antiplatelet therapy and add prophylactic-dose LMWH 1
• For carefully selected patients with favorable risk profiles, therapeutic-dose LMWH may be considered alongside antiplatelet therapy 1

Peripheral artery disease (PAD):

• Continue single antiplatelet therapy if receiving prophylactic-dose anticoagulation 1
• If on therapeutic anticoagulation, individualize whether to continue or hold antiplatelet therapy 1

Critically Ill/ICU Patients

For critically ill patients with COVID-19 on chronic anticoagulation:

• Continue therapeutic anticoagulation for the underlying indication 1
• Use LMWH as first-line agent over UFH when possible to reduce staff exposure 1
• Strongly avoid DOACs due to hemodynamic instability, high risk of drug-drug interactions, and high incidence of acute kidney injury 1
• Consider UFH over LMWH only in patients with severe renal failure (CrCl <30 mL/min) or imminent hemodynamic decompensation requiring potential rapid reversal 3
• Do not add antiplatelet agents for VTE prevention 1

Key Monitoring Parameters

Laboratory monitoring for all hospitalized patients:

• Check baseline platelet count, PT/INR, aPTT, fibrinogen, and D-dimer before initiating or continuing anticoagulation 1, 3
• Monitor D-dimer, platelet count, PT/INR, and fibrinogen every 24-48 hours during the first 7-10 days 3
• For UFH, monitor with anti-Xa assay (target 0.5-0.7 IU/mL for therapeutic dosing) rather than aPTT in critically ill patients with hyperinflammatory states 3
• Abnormal PT or aPTT alone is NOT a contraindication to thromboprophylaxis 3

Critical Bleeding Risk Assessment

Contraindications to anticoagulation:

• Active bleeding 3
• Platelet count <25 × 10⁹/L 3
• High bleeding risk conditions requiring individualized assessment 3

If bleeding occurs:

• Follow standard protocols including blood product transfusion as needed 3
• Consider anticoagulant reversal agents when appropriate based on severity and type of anticoagulant used 3

Duration of Therapy

• Continue therapeutic anticoagulation for the underlying indication throughout hospitalization and after discharge per standard guidelines for that condition 1
• Do not extend thromboprophylaxis beyond hospital discharge in patients without confirmed VTE 1
• For confirmed VTE during COVID-19 hospitalization, continue anticoagulation for minimum 3 months 3

Common Pitfalls to Avoid

• Do NOT discontinue chronic therapeutic anticoagulation simply because a patient has COVID-19 1
• Do NOT add prophylactic anticoagulation on top of therapeutic anticoagulation 1
• Do NOT use intermediate or high-dose prophylactic anticoagulation in patients already on therapeutic anticoagulation 1
• Do NOT continue DOACs in hospitalized patients due to unpredictable pharmacokinetics and drug interactions 1
• Do NOT use antiplatelet agents alone for VTE prevention in COVID-19 1