Cardiovascular/Parenteral anticoagulant (heparin)

Heparins (LMWH / unfractionated)

also: enoxaparin · dalteparin · LMWH · UFH · tinzaparin

Overview

Injectable anticoagulants for VTE prophylaxis/treatment, ACS and bridging. LMWH is the workhorse; unfractionated heparin (UFH) is used where rapid reversibility is needed.

Mechanism

Both potentiate antithrombin III. LMWH (enoxaparin/dalteparin) mainly inhibits factor Xa (predictable, weight-based, no routine monitoring). Unfractionated heparin inhibits both Xa and thrombin (IIa) — short half-life, IV infusion, monitored by APTT, fully reversible with protamine.

Indications

VTE prophylaxis (medical/surgical inpatients)
VTE treatment (incl. pregnancy — drug of choice)
ACS
Bridging anticoagulation around procedures

The agents

Enoxaparin / dalteparin / tinzaparinLMWH

SC, weight-based

No routine monitoring; renally cleared (caution/avoid or anti-Xa monitor in severe renal impairment).

Unfractionated heparinUFH

IV infusion, APTT-monitored

Short t½ + protamine reversal → preferred when bleeding risk high / peri-procedure / severe renal failure.

Adverse effects

Bleedingserious

Reverse with protamine (complete for UFH, partial for LMWH).

Heparin-induced thrombocytopenia (HIT)serious

Immune, 5–10 days in; paradoxical THROMBOSIS; commoner with UFH — stop heparin, use a non-heparin anticoagulant.

Hyperkalaemiacommon

Aldosterone suppression.

Osteoporosis (long-term)common

Cautions & contraindications

Active major bleeding / bleeding disorderall

Previous HITall

LMWH in severe renal impairmentrenal

Accumulation — use UFH or reduce/monitor.

Interactions

Other anticoagulants/antiplatelets ↑bleeding

Monitoring & kinetics

UFH: APTT. LMWH: routine none (platelets if prolonged; anti-Xa in renal failure/pregnancy/extremes of weight),Platelets for HIT

Subcutaneous (LMWH) or IV infusion (UFH). LMWH is first choice in pregnancy (does not cross placenta).

Source: BNF — Heparins · NICE NG89 — VTE