Emulsion dosage forms

L. C. Bailey, K. T. Tand, and B. A. Rogozinki, The determination of 2,6-diisopropylphenol in an oil in water emulsion dosage form by high-performance liquid chromatography and by second derivative UV spectroscopy, J. Pharm. Biomed. Anal., 9 501 (1991). 

Emulsions have been widely used as vehicles for oral, topical, and parenteral delivery of medications. Although the product attributes of an emulsion dosage form are dependent on the route of administration, a common concern is the physical stability of the system, in particular the coalescence of its dispersed phase and the consequent alteration in its particle-size distribution and phase separation. The stabilization mechanism(s) for an emulsion is mainly dependent on the chemical composition of the surfactant used. Electrostatic stabilization as described by DLVO theory plays an important role in emulsions (0/W) containing ionic surfactants. For 0/W emulsions with low electrolyte content in the aqueous phase, a zeta potential of 30 mV is found to be sufficient to establish an energy maximum (energy barrier) to ensure emulsion stability. For emulsions containing... 

This chapter describes the basic principles involved in the development of disperse systems. Emphasis is laid on systems that are of particular pharmaceutical interest, namely, suspensions, emulsions, and colloids. Theoretical concepts, preparation techniques, and methods used to characterize and stabilize disperse systems are presented. The term particle is used in its broadest sense, including gases, liquids, solids, molecules, and aggregates. The reader may find it useful to read this chapter in conjuction with Chapters 8, 12, and 14, since they include some of the most important applications of disperse systems as pharmaceutical dosage forms [1]. 

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. 

An interface is defined as a boundary between two phases. The solid/liquid and the liquid/liquid interfaces are of primary interest in suspensions and emulsion, respectively. Other types of interfaces such as liquid/gas (foams) or solid/gas interfaces also play a major role in certain pharmaceutical dosage forms, e.g., aerosols. 

TA Wheatley, CR Steuernagel. Latex emulsions for controlled drug delivery. In JW McGinity, ed. Aqueous Polymeric Coatings for Pharmaceutical Dosage Forms,... 

B Idson. Pharmaceutical emulsions. In HA Lieberman, MM Rieger, GS Banker, eds. Pharmaceutical Dosage Forms Disperse Systems, Vol. 1. New York Marcel Dekker, 1988, pp 199-244. 

Although most often connected with investigations of solid dosage forms, diffuse reflectance spectroscopy can also be used to characterize alternative formulations. Through the use of a special sample cell, the technique has been used to study the stability of emulsions [37]. In this work, it was found that information could be obtained that pointed toward subtle changes in the emulsion microenvironment. 

Aeromonas, DNA-based biosensor, 3 807 AeroSizer, 78 150—151 Aerosol containers, 7 781-782 Aerosol dispersions, 7 774-775 Aerosol drug dosage forms, 78 717 Aerosol emulsions, 7 773, 774 Aerosol flow reactors, 77 211-212 Aerosol foams, 7 773, 774 Aerosol packaging, 7 771 Aerosol pastes, 7 775 Aerosols, 7 769-787 8 697 economic aspects, 7 786 filling, 7 785-786 formulation, 7 771-780 product concentrate, 7 772-775 propellants, 7 775-781 U.S. production, 1985-2000, 7 770t Aerosol solutions, 7 772-773 Aerosol solvent extraction system (ASES), 24 17, 18... 

C. This could be attributed to the possible cross-linkages formed between the two polymers which thus restricted the movement of the drug molecules within the gel. The release of propranolol hydrochloride from the emulsion base, formulation D, was relatively low compared with all the hydrophilic polymeric gel formulations. This suggests that, for a water-soluble drug such as propranolol hydrochloride, polymeric-gel-based formulations are clearly the better vehicles for developing such dosage forms. 

Liquid dosage forms which are disperse systems (colloidal, i.e., microspheres, nanoparticles, and micelles suspensions and emulsions) often contain preservatives which are methyl, ethyl, propyl, and butyl esters of para-hydroxybenzoic acid in various combinations. A typical example is the antacid suspensions which have high pH values which make the esters of the preservatives susceptible to hydrolysis. One way to circumvent this problem is to use several preservatives in combination with the hope that some quantities of the preservatives will remain to prevent the suspension from microbial attack. A report showing the assay of the four esters and the parent acid (one of the decomposition products) in drug products in which all the preservatives were used has been given [13]. 

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