ABSTRACT
Two limbs of the coagulation pathway (intrinsic and extrinsic) converge on factor X (Figure 30.2).
Heparin is a sulphated acidic mucopolysaccharide that is widely distributed in the body. The unfractionated preparation is extracted from the lung or intestine of ox or pig, and is a mixture of polymers of varying molecular weights. Since the structure is variable, the dosage is expressed in terms of units of biological activity. Low-molecular-weight heparins (LMWH) are fragments or short synthetic sequences of heparin with much more predictable pharmacological effects, and monitoring of their anticoagulant effect is seldom needed. They have largely replaced unfractionated heparin in therapy.
