Fragmin (Dalteparin) Dosing for Acute Cerebral Infarction
Fragmin is NOT indicated for therapeutic anticoagulation in acute ischemic stroke; it should only be used at prophylactic doses for VTE prevention in immobilized stroke patients, starting 24-48 hours after symptom onset and only after excluding hemorrhagic transformation.
Primary Indication: VTE Prophylaxis Only
The evidence base for dalteparin in stroke comes exclusively from cardiac trials (unstable angina/non-Q-wave MI), not cerebral infarction. 1 The 2012 CHEST stroke guidelines explicitly recommend against therapeutic parenteral anticoagulation in acute ischemic stroke, favoring early aspirin (160-325 mg within 48 hours) instead. 1
- Prophylactic dosing for immobilized stroke patients: 5,000 IU subcutaneously once daily. 1
- Timing: Start between 24-48 hours after stroke onset, only after imaging confirms no hemorrhagic transformation. 1
- The CHEST guidelines suggest prophylactic-dose LMWH over unfractionated heparin for stroke patients with restricted mobility (Grade 2B). 1
Why Therapeutic Dosing Is Contraindicated
The cardiac dosing regimens studied in FRISC (120 IU/kg twice daily for 6 days, then 7,500 IU once daily) 1 have never been validated in acute stroke populations and carry unacceptable hemorrhagic transformation risk. The 2012 CHEST guidelines give a Grade 1A recommendation for aspirin over therapeutic anticoagulation in acute ischemic stroke. 1
Renal Function Adjustments for Prophylactic Dosing
Critical advantage: Unlike enoxaparin, prophylactic-dose dalteparin (5,000 IU daily) does not show significant bioaccumulation even in severe renal insufficiency (CrCl <30 mL/min), with peak anti-Xa levels remaining 0.29-0.34 IU/mL after 7 days. 2, 3 This makes dalteparin the preferred LMWH in stroke patients with renal impairment. 2, 4
- No dose adjustment required for prophylactic dosing in renal impairment. 2, 3
- Enoxaparin, by contrast, requires reduction to 30 mg once daily in severe renal impairment due to 44% reduced clearance and 2-3 fold bleeding risk. 2, 5, 4
Specific Clinical Scenarios Requiring Therapeutic Anticoagulation
If a stroke patient develops a separate indication requiring therapeutic anticoagulation (e.g., acute DVT/PE, high-risk atrial fibrillation with recurrent emboli, acute coronary syndrome), the dosing would be:
- Initial therapeutic dose: 200 IU/kg subcutaneously once daily for the first month. 2, 6, 7
- Maintenance dose: 150 IU/kg once daily after month 1. 2, 8
- Renal impairment (CrCl <30 mL/min): Monitor anti-Xa levels (target 0.5-1.5 IU/mL, drawn 4-6 hours post-dose after 3-4 doses). 2, 8
However, this therapeutic regimen should only be used for these separate indications, not for stroke treatment itself. 1
Common Pitfalls to Avoid
- Never use therapeutic-dose dalteparin (120 IU/kg or 200 IU/kg) for stroke treatment—this extrapolates cardiac data inappropriately and increases hemorrhagic risk. 1
- Do not start any anticoagulation within 24 hours of IV alteplase—wait for follow-up imaging to exclude hemorrhage. 5
- Avoid switching to enoxaparin in renal impairment—dalteparin's superior renal safety profile makes it the preferred agent. 2, 4, 3
- Do not use tinzaparin in elderly (≥70 years) patients with renal insufficiency—higher mortality observed in trials. 2, 4
Monitoring Requirements
- Prophylactic dosing: No routine anti-Xa monitoring required, even in renal impairment. 2, 3
- Therapeutic dosing (if separate indication exists): Monitor anti-Xa levels in severe renal impairment (CrCl <30 mL/min) or fluctuating renal function. 2, 8
- Platelet monitoring: Check platelet counts every 2-3 days from day 4-14 to screen for heparin-induced thrombocytopenia. 5