Formulation complex dispersions

The number of the constituent phases of a disperse system can be higher than two. Many commercial multiphase pharmaceutical products cannot be categorized easily and should be classified as complex disperse systems. Examples include various types of multiple emulsions and suspensions in which solid particles are dispersed within an emulsion base. These complexities influence the physicochemical properties of the system, which, in turn, determine the overall characteristics of the dosage forms with which the formulators are concerned. 

Amphotericin can cause both glomerular and tubular damage. Lipid-based formulations (colloidal dispersion, lipid complex, and liposomal amphotericin) are less nephrotoxic than conventional amphotericin deoxy-cholate (97). However, several caveats have to be kept in mind in making such comparisons. For example, there are no defined equivalent doses for amphotericin deoxycholate and its lipid-based counterparts. 

Complex Dispersions Such as Emulsions and Other Formulations... 

Amphotericin B-induced ARF occurs in as many as 40% to 65% of patients treated with the conventional desoxycholate formulation.30 Nephrotoxicity is due to renal arterial vasoconstriction and distal renal tubule cell damage. Risk factors include high doses, treatment for at least 7 days, preexisting kidney dysfunction, and concomitant use of other nephrotoxic drugs.31 Three lipid-based formulations of amphotericin B have been developed in an attempt to decrease the incidence of ARF amphotericin B lipid complex, amphotericin colloidal dispersion, and liposomal amphotericin B. The range of... 

The common concentration of a surfactant used in a formulation varies from 0.05 to 0.5% and depends on the surfactant type and the solids content of the dispersion. In practice, very often combinations of surfactants rather than single agents are used to prepare and stabilize disperse systems. The combination of a more hydrophilic surfactant with a more hydrophobic surfactant leads to the formation of a complex film at the interface. A good example for such a surfactant pair is the Tween-Span system of Atlas-ICI [71]. 

The emphasis is on commercial materials and formulations. The reason is that commercial materials are rarely pure materials. A pure homopolymer is a rare species in the real-world materials. To arrive at the desired material s properties, either a copolymer is used, sometimes a blend or a dispersion, or additives or filler materials including rubber particles, carbon black or fibres of various type and make may be added, and are thus commonplace in commercial products. This implies a more complex constitution and morphology than expected for pure polymers. However, obviously, the methods described herein can be applied to pure, unmodified, polymers as well. 

Lipid-associated formulations of amphotericin B, liposomal amphotericin B (AmBisome) and amphotericin B lipid complex (Abelcet) have been approved for use in proven cases of candidiasis however, patients with invasive candidiasis have also been treated successfully with amphotericin B colloid dispersion (Amphotec or Amphocil). The lipid-associated formulations are less toxic but as effective as amphotericin B deoxycholate. 

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