Heparin
Definition
An injectable anticoagulant
A glycosaminoglycan
LMWH - fractionated heparin containing only heparin with low molecular weight - pharmacodynamics more predictable
An essential medicine
Derivatives
Enoxaparin
Dalteparin
Tinzaparin
Fondaparinux
Indications
Deep vein thrombosis (DVT)
Pulmonary embolism
Myocardial Infarction
Unstable Angina
Coating test tubes and dialysis machines
Atrial Fibrillation
Cardiopulmonary bypass for heart surgery
Hemofiltration
Indwelling central or peripheral venous catheters
Contraindications
Catheter in the Vascular System
Severe Uncontrolled High Blood Pressure
Subacute Infection of Heart Valve,
Hemorrhage in the Brain
Stomach or Intestinal Ulcer
Ulcerated Colon,
Diverticulitis
Severe Liver Disease
Biliary and Gallbladder Problem
Severe Renal Impairment,
Possibility of Having a Miscarriage
Osteoporosis
Spinal Tap
Operation on the Spine,
Eye Surgery,
Hemophilia
Thrombocytopenia
Administration
Not absorbed from the intestine
Hence given parenterally
Routes : SC, IV
Continuous infusion, bolus dose
IM avoided (for fear of forming haematomas)
Action
Prevents formation of clot and its extension
But does not breakdown already formed clot
It allows body's natural breaking down of clots by the body's lysis mechanism (tissue plasminogen activator)
Side Effects
Pain at the site of injection
Thrombocytopenia
Hyperkalemia
With chronic use : osteoporosis, alopecia
Safety
Safe in pregnancy & breast feeding
Effect - Measurement
By the partial thromboplastin time (aPTT) - time taken to form a clot
Antidote
Protamin sulphate 1 mg per 100 units of overdose over the past four hours
(1% solution) by slow infusion
