Particle-size analysis of emulsion systems

A Simple and Noninvasive DOSY NMR Method for Droplet Size Measurement of Intact Oil-In-Water Emulsion Drug Products

In a typical oil-in-water emulsion drug product, oil droplets with varied sizes are dispersed in a water phase and stabilized by surfactant molecules. The size and polydispersity of oil droplets are critical quality attributes of the emulsion drug product that can potentially affect drug bioavailability. More critically, to ensure accuracy in characterization of the finished drug product, analytical methods should introduce minimal physical perturbation (e.g., temperature variation or dilution) before the analysis. The classical methods of dynamic light scattering or electron microscopy can be used but they generally require sample dilution or harsh preparation conditions, respectively. By contrast, the size distribution of emulsion formulations can be assessed with a simple and noninvasive solution nuclear magnetic resonance method, namely, two-dimensional Diffusion Ordered SpectroscopY. The two-dimensional Diffusion Ordered SpectroscopY method probed signal decay of methyl resonances from oil and sorbate molecules and was applied to 3 types of U.S.-marketed emulsion drug products, that is, difluprednate, cyclosporine, and propofol, yielding measured droplet sizes of 40-280 nm in diameter. The high precision of ±6 nm of the new nuclear magnetic resonance method allows analytical differentiation of lot-to-lot and brand-to-brand droplet size differences in emulsion drug products, critical for drug-quality development, control, and surveillance.

Texture Optimization of Water‐in‐Oil Emulsions

The aim of this research is to demonstrate the effect of variations in certain parameters of the oily phase (OP) in water-in-oil (W/O) emulsions on rheological and texture properties of finished products. The formulated emulsions were selected according to an optimal experimental procedure. The applied variations were nature of the OP, its volume fraction, the hydrophilic-lipophilic balance (HLB) value, and the surfactant proportion. Results are presented for the followed tests carried out on the emulsions: texture analysis, rheology, and particle size analysis. The oils used in the study were sweet almond oil, liquid paraffin, maize oil, cyclomethicone, dimethicone, and wheat germ oil. The resulting data demonstrate a notable influence of the volume fraction oil on hardness, viscosity, adhesiveness, and cohesiveness of W/O emulsions. Emulsion hardness and viscosity increased as the OP percentage increased; this effect being even more pronounced for the vegetable oils. In contrast, emulsion adhesiveness and cohesiveness decreased as the volume fraction oil increased. The HLB value of the surfactant mixture of the emulsion also influenced hardness, adhesiveness, and elasticity, increasing or decreasing as HLB value did.

Prolonged release of rifampicin from multiple w/o/w emulsion systems

The formation of multiple w/o/w emulsions with improved stability by using interfacial complex films between polyvinyl alcohol, acacia, polyvinylpyrrolidone and sorbitan monooleate (Span 80) is described. The long term stability of the emulsions, as assessed by microscopy and particle size analysis, showed no changes in the w/o/w emulsion systems prepared using these macromolecules in the internal phase. It has also been observed that the release rate of rifampicin, contained in the internal phase, increased significantly on addition of calcium stearate and/or soya lecithin to the organic phase.

Simple, rapid method for comparing the self-emulsifiability of hydrocarbon oils

A simple and rapid method for comparing the degree of self-emulsifiability of different hydrocarbon oils is described. The method involved measurement of the intensity of light scattered at an angle of 31 degrees to the incident radiation by the sample. The extent or degree of self-emulsification of selected hydrocarbon oils was observed to be affected by the nature of the oil as well as by the type and concentration of the surfactants employed. The method is useful when screening surfactant-hydrocarbon oil combinations as potential vehicles for drugs in the pharmaceutical industry or herbicides and pesticides for agricultural purposes.

Formulation and evaluation of ethiodized oil emulsion for intravenous hepatography

A study was conducted to prepare and evaluate an ethiodized oil emulsion for intravenous administration that would selectively opacify the liver. Several formulations with differing globule size were prepared and compared for their in vivo activity (degree of liver opacification obtained) and stability. Results of studies conducted in rabbits and monkeys revealed that the oil globules that concentrate most in liver were 2.0--3.0 micrometer in diameter. The formulation of choice was stable for 6 months at refrigeration temperature (2--6 degree). In monkeys, this formulation produced an improved diagnostic image of the liver using computerized tomography at a dose of 0.2 ml/kg. The potential use of such emulsions in diagnostic radiology is briefly discussed.