Core pharmacology

Class Group

Anticoagulants

Legacy Cicm Level

Level 1

Introduction

Heparin is an anioic, mucopolysaccaride,
organic acid. It occurs naturally in the liver and mast cell granules.

MW: 5000-25000 Daltons

Indications Uses

1. the prevention of venous thromboembolic disease
2. the priming of haemodialysis and cardiopulmonary bypass machines
and for maintaining the patency of indwelling lines and the treatment of
3. DIC
4. fat embolism, and
5. in the treatment of acute coronary syndromes.

Presentation

s/c or i.v. - I.U. (not mg) due to variable potencies. 5000IU BD s/c or 5000IU IV then infusion-rate based on wttitrated (APTT)

Mechanism of action

Activates antithrombin which then inhibits clotting factors thrombin and factor Xa

Adverse Effects Toxicity

Bleeding, Heparin Induced Thrombocytopaenia, Osteoporosis,
Transient transaminitis

Absorption

reduced due to endothelial binding (SC), IV

Protein binding

very high protein binding.

Volume of distribution

Vd 0.05-0.1L/kg

Metabolism

By heparinases in the liver,
reticuloendothelial system and kidneys

Excretion

urine as inactive metabolites, little change in renal failure

Half-life

variable half life due to protein binding 30 - 150 mins depending on dose

Special Points

Reversal:
Protamine by slow infusion (1mg/100i.u.
heparin). Cationic compound forms a stable covalent salt with heparin