Unfractionated Heparin (ACS / PCI)

How it works

It binds antithrombin and greatly accelerates its inactivation of thrombin (factor IIa) and factor Xa, thereby inhibiting fibrin formation and thrombus propagation.

Prescribing in practice

• Bleeding is the major risk and should be weighed against thrombotic benefit; its anticoagulant effect can be reversed with protamine if serious haemorrhage occurs.
• Heparin-induced thrombocytopenia is an important immune-mediated complication, so platelet counts should be monitored and the drug stopped if it is suspected.
• It is contraindicated in active major bleeding and in known heparin-induced thrombocytopenia, with caution near surgery or recent trauma.

Monitoring

Monitor the activated partial thromboplastin time (or anti-Xa) for therapeutic intravenous infusions, together with platelet count and haemoglobin, adjusting the rate to target.

Counselling the patient

• This is a hospital anticoagulant that increases the risk of bleeding.
• Report any unusual bruising, bleeding or new pain or swelling.
• Tell the team about any prior reaction to heparin.

Evidence & guidelines

Unfractionated heparin is established standard anticoagulation in acute coronary syndromes and PCI, and its use is embedded in NICE and ESC guidance for these settings.