Dalteparin
Dalteparin sodium is a **low molecular weight (fractionated) heparin (LMWH)** used primarily for the prevention and treatment of thromboembolic diseases. * **Mechanism Advantage**: Unlike unfractionated heparin (UFH), LMWHs like dalteparin have a more predictable pharmacokinetic profile and preferentially target Factor Xa over thrombin, reducing the risk of spontaneous hemorrhage. * **Veterinary Challenges**: While highly effective in humans with once or twice daily dosing, dogs and especially cats eliminate dalteparin very rapidly. This necessitates frequent subcutaneous injections (up to every 4-6 hours in cats), which can make long-term outpatient management highly impractical and expensive. * **Clinical Utility**: Often utilized in critical care settings for patients at high risk of thrombosis (e.g., immune-mediated hemolytic anemia, protein-losing nephropathy, feline aortic thromboembolism, or equine colic).
Mechanism: Dalteparin exerts its anticoagulant effect by binding to and accelerating **antithrombin III (ATIII)**. * **Conformational Change**: Binding induces a conformational change in ATIII, significantly accelerating its ability to inactivate coagulation factors. * **Factor Xa Selectivity**: Because dalteparin consists of shorter polysaccharide chains (average molecular weight ~5000 daltons) compared to unfractionated heparin, it lacks the chain length required to simultaneously bridge ATIII and thrombin (Factor IIa). Therefore, it preferentially inhibits **Factor Xa**. * **Pathway**: Dalteparin + ATIII → **Potent inhibition of Factor Xa** → Decreased conversion of prothrombin to thrombin → Prevention of fibrin clot formation. *Clinical Pearl*: Because it minimally impacts thrombin, routine clotting times like TT or aPTT are usually unaffected and are poor monitoring tools for this drug.
Dosing by species
- Thromboembolic disease prophylaxis/treatment · 150 Units/kg · SC · q4h · Required to maintain a therapeutic target of anti-XA activity of 0.5-1 IU/mL.
- Thromboembolic disease prophylaxis/treatment · 180 Units/kg · SC · q4-6h · Current clinical dose recommendation.
- Prophylaxis of coagulation disorders in colic patients · 50 Units/kg · SC · q24h · Once daily dosing.
- Thromboembolic disease prophylaxis/treatment · 150 Units/kg · SC · q8h · Initial dose 150 Units/kg SC q8h.
- Thromboembolic disease prophylaxis/treatment · 150 Units/kg · SC · TID or BID · 150 Units/kg SC three times daily; twice daily dosing may be effective. Studies are ongoing.
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Routes of administration
Contraindications
- Hypersensitivity to dalteparin, heparin, or pork products
- Active major bleeding
- Heparin-induced thrombocytopenia
- Thrombocytopenia associated with positive in vitro tests for anti-platelet antibodies in the presence of dalteparin
- Intramuscular (IM) or Intravenous (IV) administration
Adverse effects
- Hemorrhage (unlikely but possible)
- Injection site hematomas or pain
- Allergic reactions
- Neurologic sequelae secondary to epidural or spinal hematomas
Drug interactions
- Warfarin · Increased risk for hemorrhage
- Aspirin · Increased risk for hemorrhage
- Clopidogrel · Increased risk for hemorrhage
- Thrombolytic agents · Increased risk for hemorrhage
Monitoring
- Baseline and ongoing CBC (with platelet count)
- Urinalysis
- Stool occult blood test
- Factor Xa activity (Note: To measure peak anti-Xa activity in cats, sample at 2 hours post-dose)
Overdose
Overdosage may lead to hemorrhagic complications. If treatment is necessary, **protamine sulfate** via slow IV may be administered. * **Dose ratio**: 1 mg of protamine sulfate can inhibit the effects of 100 units of administered anti-Xa dalteparin. * **Caution**: Avoid overdoses of protamine, as it has its own anticoagulant properties and can cause severe hypotension or anaphylactoid reactions.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.