Investigation of thermodynamic properties of the binary system polyethylene glycol/CO2 using new methods

Solvent-free method for masking the bitter taste of azithromycin dihydrate using supercritical fluid technology

INTRODUCTION AND PURPOSE

The unpleasant extremely bitter taste of the orally administered broad-spectrum antibiotic azithromycin decreases patient compliance, especially in pediatrics. This issue can be overcome by decreasing drug interaction with the tasting buds using insoluble polymers at salivary pH (6.8 - 7.4), like the cationic polymer Eudragit EPO. Supercritical fluid technology is a green synthesis method for preparing pharmaceutical preparations that replace organic solvents with safe supercritical CO2. This study aimed to mask the bitter taste of azithromycin using the supercritical fluid method and a pH-sensitive Eudragit EPO polymer.

METHODS

A foaming process was investigated for preparing a formulation (TEST), which comprises treating the polymer with supercritical carbon dioxide (CO2) fluid to prepare a taste-masked dosage form without employing organic solvents or flavors.

RESULTS

The use of the supercritical technique at 40 °C and 10 MPa for 2 h allowed the manufacturing of solvent-free polymeric foam with azithromycin dispersions; the average calculated percentage of apparent volume change was 62.5 ± 5.9% with an average pore diameter of 34.879 Å. The formulated sample showed low drug release in simulated salivary fluid while keeping its crystalline nature. Moreover, clinical studies on healthy subjects showed that the formula successfully masked azithromycin's bitter taste.

CONCLUSIONS

Overall, it has been shown herein that the supercritical fluid technology foaming method is promising in masking the bitter taste of bitter ingredients.

Amorphous Polymers' Foaming and Blends with Organic Foaming-Aid Structured Additives in Supercritical CO2, a Way to Fabricate Porous Polymers from Macro to Nano Porosities in Batch or Continuous Processes

Organic polymers can be made porous via continuous or discontinuous expansion processes in scCO2. The resulting foams properties are controlled by the interplay of three groups of parameters: (i) Chemical, (ii) physico-chemical, and (iii) technological/process that are explained in this paper. The advantages and drawbacks of continuous (extrusion, injection foaming) or discontinuous (batch foaming) foaming processes in scCO2, will be discussed in this article; especially for micro or nano cellular polymers. Indeed, a challenge is to reduce both specific mass (e.g., ρ < 100 kg·m-3) and cell size (e.g., average pore diameter ϕaveragepores < 100 nm). Then a particular system where small "objects" (coreshells CS, block copolymer MAM) are perfectly dispersed at a micrometric to nanometric scale in poly(methyl methacrylate) (PMMA) will be presented. Such "additives", considered as foaming aids, are aimed at "regulating" the foaming and lowering the pore size and/or density of PMMA based foams. Differences between these additives will be shown. Finally, in a PMMA/20 wt% MAM blend, via a quasi one-step batch foaming, a "porous to nonporous" transition is observed in thick samples. A lower limit of pore size (around 50 nm) seems to arise.

Supercritical Fluids as a Tool for Green Energy and Chemicals

Hydrothermal conversion of biomass is a promising technology for the conversion of biomass into biofuels and biobased chemicals. This chapter is focused on the waste biomass conversion for production of biofuels and chemicals by applying sub- and supercritical fluids. One of the biggest disadvantages in biomass conversion by SCF is the extremely high energy requirement for heating the media above the water critical point (374 °C, 221 bar). The idea behind the recent research is to reduce the operating temperature and energy requirements by processing biomass with water at much higher pressures. The importance of knowledge on behavior of multicomponent systems at elevated pressures and temperatures is underlined. Methods, developed by the authors of this chapter for determination of thermodynamic and transport properties for multicomponent systems of different solid compounds and supercritical fluid under extreme conditions are described. Future perspective of hydrothermal technology as a tool to obtain advanced materials and the possible scope for future research is also discussed.