Which anticoagulants contraindicate the use of intravenous thrombolytic therapy (tPA) for acute ischemic stroke?

Anticoagulants That Contraindicate IV Thrombolysis for Acute Ischemic Stroke

You cannot give IV thrombolysis (tPA) to stroke patients on therapeutic UFH, LMWH, or fondaparinux, and you should not give it to patients on warfarin with INR >1.7 or those on DOACs with levels ≥100 ng/mL. 1

Absolute Contraindications Based on Anticoagulant Type

Heparin Products (Strongest Contraindication)

• Unfractionated heparin (UFH) at therapeutic doses
• Low-molecular-weight heparin (LMWH) within the last 24 hours
• Fondaparinux at therapeutic doses

Do not give IV thrombolysis to any patient on these agents 1. The guidelines provide no pathway for reversal or waiting periods—these are hard stops. For UFH specifically, there is insufficient evidence to recommend protamine sulfate reversal prior to thrombolysis 1.

Warfarin (VKA) - INR-Dependent Decision

The decision hinges entirely on the INR:

• INR ≤1.7: Proceed with IV thrombolysis 1
• INR >1.7: Do NOT give IV thrombolysis, even after reversal with vitamin K or PCC 1

This INR cutoff of 1.7 is a firm threshold. The 2025 French guidelines explicitly state that VKA reversal does not make thrombolysis safe when INR exceeds 1.7, reflecting the persistently elevated bleeding risk 1.

Direct Oral Anticoagulants (DOACs) - Concentration-Dependent Algorithm

For patients who took DOACs within the last 48 hours, the decision depends on drug levels:

Anti-Xa DOACs (apixaban, rivaroxaban, edoxaban):

• <50 ng/mL: Proceed with IV thrombolysis 1
• 50-100 ng/mL: Consider case-by-case (gray zone) 1
• ≥100 ng/mL: Do NOT give IV thrombolysis 1

Dabigatran (direct thrombin inhibitor):

• <50 ng/mL OR thrombin time <60 seconds: Proceed with IV thrombolysis 1
• After idarucizumab 5g IV reversal: Proceed with IV thrombolysis 1
• 50-100 ng/mL: Consider case-by-case 1

Critical caveat: Do NOT use PCCs or andexanet alfa to reverse DOACs for the purpose of giving thrombolysis—reversal agents are not recommended in this context 1.

Additional Coagulation Parameters

Beyond specific anticoagulants, the 2018 AHA/ASA guidelines specify that IV alteplase should not be administered when 2:

• Platelets <100,000/mm³
• INR >1.7
• aPTT >40 seconds
• PT >15 seconds

If you don't know the platelet count or coagulation parameters and the patient has no history of anticoagulant use, you can start thrombolysis but must stop immediately if abnormal values return 2.

Practical Implementation

The algorithm is straightforward:

1. Check anticoagulant history within 48 hours
2. If on UFH, LMWH, or fondaparinux therapeutically → No thrombolysis
3. If on warfarin → Check INR immediately:
   • ≤1.7 → Proceed

   • 1.7 → No thrombolysis

4. If on DOAC within 48h → Measure drug level:
   • <50 ng/mL → Proceed (or use idarucizumab for dabigatran)
   • 50-100 ng/mL → Individualize based on stroke severity, time window, and bleeding risk
   • ≥100 ng/mL → No thrombolysis

Important Nuances

Thrombectomy remains an option regardless of anticoagulation status. The 2025 guidelines strongly recommend considering mechanical thrombectomy for proximal occlusions whether or not thrombolysis was performed 1. This is critical because many patients excluded from thrombolysis due to anticoagulation can still receive definitive reperfusion therapy.

The evidence base differs by anticoagulant. The warfarin INR threshold comes from observational data showing increased symptomatic ICH rates (10.4% vs 5.4%) in patients with elevated INRs 1. For DOACs, emerging observational data suggests thrombolysis may be safer than previously thought when drug levels are low 3, 4, but the 2025 guidelines maintain conservative thresholds based on expert consensus given the lack of randomized trials 1.

Timing matters for DOACs. If the last DOAC dose was >48 hours ago AND renal function is normal, anticoagulant activity should be minimal and thrombolysis can be considered even without drug level testing 2. However, this assumes normal renal clearance—adjust for renal impairment.

The 2012 ACCP guidelines are more restrictive than current practice, recommending against therapeutic anticoagulation entirely in acute stroke 5. The 2025 French guidelines represent the most current, nuanced approach to anticoagulated patients 1.