Adhesive granulating agents

Often, a binding or adhesive granulating agent is required which may be added in solution or mixed with the tablet ingredients as a dry powder for subsequent activation by moisturing with an appropriate solvent. Many binders are hydrophilic colloids as, for example, polysaccharides (Table 5). 

For a granulating agent to be effective, it is vital that it is able to form a film on the particle surface. Rowe (1989) has suggested that binders should be selected on the basis of their spreading coefficients, where the spreading coefficient is defined as the difference between the work of adhesion of the binder and the substrate and the work of cohesion of the binder. The commonly used granulating agents are listed in Table 11.13. 

Thirdly, there are the selectins, a family of Ca Mependent carbohydrate-binding proteins which function to control leukocyte interactions with vascular endothelium (Tedder et al, 1995). There are three closely related members of the selectin family, namely L (leukocyte)-, P (platelet)-, and E (endothelial)-selectin. P-selectin is expressed in the Weibel-Palade bodies of endothelial cells and in the a-granules of platelets. It is rapidly mobilized to the sur ce of endothelial cells and platelets in response to a variety of inflammatory agents such as fiuombin, histamine, complement factors, fiee radicals and cytokines (Tedder et al, 1995). P-selectin mediates the adhesion of neutrophils and monocytes to activated platelets and endothelial cells. Platelets can be bound to the endothelium indirectly by adhering to leukocytes bound to the endothelium. 

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