💉 Low Molecular Weight Heparin (LMWH) Used for prevention and treatment of thrombosis. 📖 Always consult the BNF or local trust guidelines for exact dosing and monitoring.

🩺 Overview

🧬 LMWH is derived from unfractionated heparin (UFH) by controlled depolymerisation.
📊 Produces a predictable anticoagulant response.
🎯 Predominantly anti–Factor Xa activity.
⚖️ Allows weight-based dosing without routine lab monitoring in most patients.
🫀 Lower risk of HIT and osteoporosis than UFH.
🚽 Renally excreted → dose reduction required in renal impairment.

🧠 Clinical principle: LMWH simplifies anticoagulation, but renal function must always be checked first.

⚙️ Mechanism of Action

🔗 Binds to antithrombin III.
⛔ Accelerates inactivation of Factor Xa.
📉 Smaller effect on thrombin (Factor IIa) than UFH.
💉 Given subcutaneously.
⚠️ Protamine only partially reverses its effect.

🎯 Clinical Indications

🩸 Prevention of VTE in medical and surgical patients.
🚑 Treatment of DVT and PE.
❤️ Acute coronary syndromes.
🏥 Bridging therapy around procedures.
🤰 Anticoagulation in pregnancy (preferred over warfarin).
🦠 Cancer-associated thrombosis.

🚫 Contraindications & Cautions

⛔ High Bleeding Risk
- Thrombocytopenia, haemophilia.
- Severe liver failure.
- Severe renal impairment.
- Uncontrolled hypertension (>200/120).
- Active GI ulceration.
- Varices, aneurysm, proliferative retinopathy.
- Recent major surgery (brain, spine, eye).
- Recent intracranial haemorrhage.
⚠️ Heparin-Induced Thrombocytopenia (HIT)
- Previous HIT = absolute contraindication.
- Use alternative anticoagulant.

🔍 Monitoring

🧪 Anti–Factor Xa Levels (not routine)
- Severe renal impairment.
- Extreme body weight (<40 kg or >150 kg).
- Pregnancy (some protocols).
- Unexpected bleeding or thrombosis.
🩸 Platelet Count
- Baseline and periodic checks.
- Drop >50% → suspect HIT.
🧪 Renal function (U&Es) before and during therapy.

💊 Common Formulations (UK)

Enoxaparin
Tinzaparin
Dalteparin
Fondaparinux (synthetic Xa inhibitor; LMWH-like use)

⚠️ Formulations are not interchangeable on a unit-for-unit basis.

⚠️ Side Effects

🩸 Bleeding
- Most important complication.
- Only partially reversible.
🧪 Hyperkalaemia
- Due to aldosterone suppression.
- More likely with prolonged use.
📉 Thrombocytopenia (HIT)
- Immune-mediated.
- Paradoxical thrombosis.
- Stop all heparins immediately.
🦴 Osteoporosis
- With long-term use (>20 weeks).
💉 Injection-site reactions

🩺 Practical Prescribing Tips

📏 Always calculate dose using actual body weight.
🫀 Check eGFR before prescribing.
💉 Inject into abdominal wall; rotate sites.
🚫 Avoid IM injections during therapy.
📋 Document indication and duration.
🔁 Review daily in inpatients.

💡 Safety Pearl: Any new thrombosis + falling platelets on LMWH = HIT until proven otherwise.

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Heparin - Low Molecular Weight Heparin 💊