This survey of the pharmaceutical aspects of polymers and macromolecules emphasises their use as formulation aids. It stresses the key features of polymers – their molecular weight distribution and their versatility in terms of their morphology, crystallinity, solubility and performance. It is convenient to think of polymeric systems as either water-soluble or waterinsoluble (this division, while not rigid as some polymers are water-dispersible, is useful in that it separates the two main areas of use which form the basis of this chapter). Water-soluble materials are used to modify the viscosity of aqueous solutions and to maintain the stability of suspensions, to form the basis of film coatings and as the basis of water-soluble matrices (for example, the polyoxyethylene glycols as suppository bases). Water-insoluble materials form membranes and matrices: the factors affecting the transport of drugs in the systems should be monitored – the thickness of the membrane, the solubility of the drug in the membrane and the relationship of this to its lipophilicity generally, copolymer ratios, porosity and heterogeneity of the mix caused by fillers or plasticisers.
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