Low Molecular Weight Heparin (Dalteparin, Enoxaparin)
**Low molecular weight heparin (LMWH)**, including **dalteparin** and **enoxaparin**, is an anticoagulant used to treat thromboembolic complications and hypercoagulable syndromes such as pulmonary thromboembolism (PTE) and immune-mediated haemolytic anaemia (IMHA). > **Clinical Warning:** Its use in Disseminated Intravascular Coagulation (DIC) is controversial and it is no longer used to try to prevent DIC. Heparins are only effective if sufficient **Antithrombin III (AT III)** is present. **Clinical Pearl:** LMWH has better pharmacokinetic properties than unfractionated heparin (UFH) and its actions are more predictable, though it is considerably more expensive.
Mechanism: LMWH is an anticoagulant that inhibits **Factor Xa** and **thrombin**. * Compared with unfractionated heparin (UFH), LMWH has reduced anti-IIa activity relative to anti-Xa activity (ratio of anti-Xa to anti-IIa is 2-4:1 compared with UFH 1:1). * → At therapeutic doses, LMWH has minimal effect on aPTT. * → Therapeutic monitoring is performed by measuring **anti-Xa activity**.
Dosing by species
- Thromboembolic complications and hypercoagulable syndromes · Target anti-Factor Xa activity of 0.35-0.7 IU/ml · SC/IV · variable · As directed · Doses are controversial. Requires sufficient AT III. May use constant IV infusions.
- Thromboembolic complications and hypercoagulable syndromes · Target anti-Factor Xa activity of 0.35-0.7 IU/ml · SC/IV · variable · As directed · Cats appear to require higher dosages of LMWH to achieve proposed therapeutic targets.
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Routes of administration
Contraindications
- Bleeding disorders
- Severe renal dysfunction
Adverse effects
- Haematoma formation (if administered IM)
- Haemorrhage (especially in thrombocytopenic patients or those with DIC)
Drug interactions
- Aspirin · Can cause changes in coagulation status, increasing bleeding risk · major
- NSAIDs · Can cause changes in coagulation status, increasing bleeding risk · major
- ACTH · Heparin may antagonize ACTH · moderate
- Corticosteroids · Heparin may antagonize corticosteroids · moderate
- Insulin · Heparin may antagonize insulin · moderate
- Diazepam · Heparin may increase plasma levels of diazepam · moderate
- Antihistamines · May partially counteract the actions of heparin · minor
- Digoxin · May partially counteract the actions of heparin · minor
- Tetracyclines · May partially counteract the actions of heparin · minor
Monitoring
- Anti-Factor Xa activity (target 0.35-0.7 IU/ml)
- aPTT (Activated partial thromboplastin time)
- PT (Prothrombin time)
- Fibrin degradation products
- Fibrinogen
- Clinical signs of bleeding
Overdose
If an overdosage occurs, **protamine** can be used as an antidote.
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.