Formulation of insoluble drugs. Study of pharmaceutical suspensions by response surface methodology

The preformulation of insoluble drugs, sulfadiazine and aluminium hydroxyde, were studied in order to achieve a suspension with desirable requirements. The objective of the formulator is to avoid the irreversible aggregation called “caking", and to obtain a suspension with an airy, large volume sediment easily redispersible and with suitable rheological properties. An experimental design useful to determine optimal properties is a Central Composite Design. The surfactant, thickener and electrolyte at different proportions are the 3 factors studied. This strategy allows to point on the main significant effect and to determine the concentrations of each product leading to optimal properties of the suspensions

EO/EP copolymer membranes as reservoir in a transdermal therapeutic system for caffeine deliveryModeling and simulation

International audienc

Solutions, suspensions et émulsions destinées aux voies orale, parentérale et ophtalmique

International audienc

Preparation and Evaluation of Microemulsion Systems Containing Salicylic Acid

Microemulsions (MEs) are clear, thermodynamically stable systems. They were used to solubilize drugs and to improve topical drug availability. Salicylic acid (SA) is a keratolytic agent used in topical products with antimicrobial actions. The objective of this work was to prepare and evaluate SA ME systems. Different concentrations of SA were incorporated in an ME base composed of isopropyl myristate, water, and Tween 80: propylene glycol in the ratio of 15:1. Three ME systems were prepared: S2%, S5%, and S10% which contain 2%, 5%, and 10% of SA, respectively. Evaluation by examination under cross-polarizing microscope, measuring of percent transmittance, pH measurement, determination of the specific gravity, assessment of rheological properties, and accelerated stability study were carried out. The data showed that the addition of SA markedly affected the physical properties of the base. All systems were not affected by accelerated stability tests. Stability study for 6 months under ambient conditions was carried out for S10%. No remarkable changes were recorded except a decrease in the viscosity value after 1 month. The results suggested that ME could be a suitable vehicle for topical application of different concentrations of SA

Shear localisation in interfacial particle layers and its influence on Lissajous-plots

Interfacial rheological measurements often show in their nonlinear Lissajous-plots rhombus or saddle-like shapes indicating complex local deformation behaviour. A strong interacting silica particle and an almost not interacting clay particle were studied in respect to their interfacial rheological properties. Large amplitude oscillation shear measurements were performed with a bicone geometry and combined with optical measurements, from which particle tracks were calculated. A correlation was found between the appearance of shear localisation and Lissajous-plot shapes. Silica particles showed shear localisation at the bicone edge and rhombic plateaus in the Lissajous-plot, while the shear localisation for the clay particles was observed at the cup's wall as saddle-like shaped Lissajous-plots