Water dispersions melt dispersion technique

Water-soluble drugs cannot be encapsulated with the 0/W-emulsion technique because the drug would be lost to the external aqueous phase. Two methods have been described for the encapsulation of hydrophilic drugs one is based on using an external oil phase and the other one on the formation of the microparticles by a w/o/w-melt dispersion technique. 

This chapter will discuss (a) the production and characterization of LS formed by the melt dispersion technique, by the solvent evaporation method, and by the water/oil/water (w/o/w) double-emulsion method (b) the influence of preparation parameters on liposphere morphology and (c) the encapsulation efficiency and the release characteristics of two lipophilic model drugs, such as retinyl acetate and progesterone, and one hydrophilic drug, sodium cromoglycate (SCG), from the prepared LS. 

Beside solvent application techniques, these resins can be applied as hot melts and from water dispersions. Water dispersions (12. 14) may be readily prepared by converting amine end groups to salts such as substituted ammonium acetates. These intrinsic emulsifiers readily cause water dispersions called suspensoids. Films from suspensoids must be heat fused in order to achieve barrier properties. 

The use of waxes in pharmaceutical and food industry is a common practice. Their main use, as described previously, is to play the role of wall material in melt-dispersion technique and widely in melt techniques. The extent of this use stans from the advantages that waxes have as components intended for human use. These advantages include good chemical and physical stability at varying pH values and moisture levels, well-established safe use in humans due to their nonswellable and water-insoluble nature, and minimal effect on food. ... 

The effects of cholesterol on phospholipid dispersions in water have been studied by a variety of biophysical techniques. These have created an understanding of the cholesterol condensation eff t in molecular terms. Such studies have been made above and below the main phosphohpid melting transition temperature (7 ) at which the phosphohpid changes from the l-)8 gel phase to the L-a hquid-crystalline phase. 

There is a type of melt-dispersion technology, which actually represents a combination of melt-dispersion and emulsification technique. Namely, a melt (dispersed phase) is fed into a vessel containing water (continuous phase) wherein mechanical stirring is used for dispersing it thus, mixing is performed simultaneously with cooling (Figure 25.2). 

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