A patient with acute pulmonary embolism who is taking apixaban (Eliquis) at home—should they be started on an unfractionated heparin infusion?

No, do not start heparin drip—continue the apixaban (Eliquis) the patient is already taking at home.

For a patient with acute PE already on therapeutic apixaban at home, continuing the apixaban is the appropriate management strategy rather than switching to unfractionated heparin. The FDA label for Eliquis explicitly states that "initiation of ELIQUIS is not recommended as an alternative to unfractionated heparin for the initial treatment of patients with PE who present with hemodynamic instability or who may receive thrombolysis or pulmonary embolectomy" 1—meaning apixaban IS appropriate for hemodynamically stable PE, which is the vast majority of cases.

Clinical Decision Algorithm

Step 1: Assess Hemodynamic Stability

• If hemodynamically UNSTABLE (systolic BP <90 mmHg, shock, requiring pressors):

  • Stop apixaban
  • Start UFH bolus (80 U/kg) followed by infusion (18 U/kg/hr) 2
  • Consider systemic thrombolysis 2

• If hemodynamically STABLE (which is >95% of PE cases):

  • Continue home apixaban at treatment dose
  • Verify correct dosing: Should be 10 mg twice daily for first 7 days, then 5 mg twice daily 3, 4, 1

Step 2: Verify Therapeutic Dosing

Check if the patient is on the correct apixaban dose for acute VTE treatment:

• Correct acute PE dosing: 10 mg PO BID × 7 days, then 5 mg PO BID 3, 1
• If on prophylactic dose (2.5 mg BID): Increase to treatment dose
• If on atrial fibrillation dose (5 mg BID): Increase to 10 mg BID for first week

Step 3: Assess for Contraindications to Continuing Apixaban

Switch to heparin ONLY if:

• Severe renal impairment (CrCl <15-25 mL/min) 5
• Active major bleeding requiring reversal
• Need for urgent invasive procedure within 24-48 hours 1
• Concern for medication non-adherence requiring monitored therapy
• Antiphospholipid antibody syndrome 2, 6

Why Not Switch to Heparin?

Apixaban is non-inferior to heparin/warfarin for acute VTE treatment with significantly lower bleeding risk. In the AMPLIFY trial, apixaban showed comparable efficacy (2.3% vs 2.7% recurrent VTE) but superior safety (0.6% vs 1.8% major bleeding, P<.001) compared to enoxaparin/warfarin 5.

The 2018 NCCN guidelines explicitly list apixaban as an acceptable monotherapy option for acute PE treatment, requiring no lead-in parenteral anticoagulation 3. The 2020 ESC guidelines recommend DOACs (including apixaban) in preference to vitamin K antagonists for acute PE 2, and the 2020 ASH guidelines conditionally recommend DOACs over VKAs 6.

Common Pitfalls to Avoid

1. Don't reflexively switch to heparin just because the patient is hospitalized—this outdated practice increases bleeding risk without improving efficacy 7, 8

2. Don't order anti-Xa levels to "monitor" apixaban—these are not validated for dose adjustment and should not guide therapy 9

3. Don't bridge with heparin if already on therapeutic apixaban—the patient is already anticoagulated. Bridging adds bleeding risk without benefit 4

4. Don't use UFH for convenience of "reversibility"—apixaban has a 12-hour half-life and can be held 24-48 hours before procedures 1. UFH requires continuous monitoring, has higher bleeding rates, and risks heparin-induced thrombocytopenia 10

Special Circumstances

If the patient has cancer: Apixaban remains acceptable, though LMWH (dalteparin or enoxaparin) is preferred for the first 6 months based on stronger cancer-specific evidence 3. However, if already on apixaban with good adherence, continuation is reasonable.

If severe renal dysfunction (CrCl <30 mL/min): UFH becomes the preferred agent as it is hepatically cleared 5, 10. Dose: 80 U/kg bolus, then 18 U/kg/hr, target aPTT 1.5-2.5× control 10, 11.

If interventional therapy is being considered: Continue apixaban unless catheter-directed thrombolysis is imminent—in which case, hold apixaban and do NOT start heparin until after the procedure 1.