Preparation of Theophylline-Hydroxypropylmethylcellulose Matrices Using Supercritical Antisolvent Precipitation: A Preliminary Study

An overview on the mathematical modeling of hydrogels' behavior for drug delivery systems

Hydrogels-based systems (HBSs) for drug delivery are nowadays extensively used and the interest in modeling their behavior is dramatically increasing. In this review a critical overview on the modeling approaches is given, quantitatively and qualitatively analyzing the publications on the subject, the trend of the publications per year and the type of modeling approaches. It was found that, despite the drug release fitting models (i.e. Higuchi's equation) are the most abundant, their use for HBSs is decreasing in the last years and luckily, considering the limiting assumption on which they were built, they will be confined to simple mathematical fitting equations. Within the mechanistic models the "multi-component" with the swelling approximation (mass transport only) and with the mechanics (fully coupled) are experiencing the highest growth rate, with much more interest toward the last one that, in the next years could be able to provide a first principles model. Statistical models, especially based on the response surface methodology, are rapidly spreading in the scientific community mainly thanks to their ability to be predictive, regardless of the phenomenology, in the analyzed design space with very low efforts. Neural Networks models for HBSs, in countertrend with their use in the pharmaceutical industry, have never take off preferring less data demanding statistical models.

Supercritical Fluid Technology: An Emphasis on Drug Delivery and Related Biomedical Applications

During the past few decades, supercritical fluid (SCF) has emerged as an effective alternative for many traditional pharmaceutical manufacturing processes. Operating active pharmaceutical ingredients (APIs) alone or in combination with various biodegradable polymeric carriers in high-pressure conditions provides enhanced features with respect to their physical properties such as bioavailability enhancement, is of relevance to the application of SCF in the pharmaceutical industry. Herein, recent advances in drug delivery systems manufactured using the SCF technology are reviewed. We provide a brief description of the history, principle, and various preparation methods involved in the SCF technology. Next, we aim to give a brief overview, which provides an emphasis and discussion of recent reports using supercritical carbon dioxide (SC-CO2 ) for fabrication of polymeric carriers, for applications in areas related to drug delivery, tissue engineering, bio-imaging, and other biomedical applications. We finally summarize with perspectives.

Melt extruded helical waxy matrices as a new sustained drug delivery system

The aim of this research was to prepare helical and cylindrical extrudates by melt extrusion and to evaluate their potential as sustained release dosage form. The systems contained theophylline as water-soluble model drug and microcrystalline wax as thermoplastic binder. The temperature suitable to ensure a successful extrusion process of formulations containing the wax in three different percentages was found to be below the melting point of the excipient. After the production of the extrudates in three different helical shapes (having 2, 3 and 4 blades) and a classical cylindrical shape, the systems were studied by means of X-ray powder diffraction and differential scanning calorimetry to check possible variations of the solid state of the drug during the thermal process. The morphology and chemical composition of the surface of the extrudates were examined by Scanning Electron Microscopy/Energy Dispersive X-ray Microanalysis to evaluate the presence of the drug on the surface of the extrudates and to monitor changes on the aspect of the waxy matrix during dissolution. Then, the different systems were analysed from the in vitro dissolution point of view to study the influence of the shape and of the composition on the drug release. An in vivo pilot study on the best performing system (helix with 3 blades) was carried out on five healthy volunteers and monitoring the intestinal transit by X-ray images. The resulting plasma profiles were analysed by means of a suitable pharmacokinetic analysis. Finally, an ad hoc mathematical model was developed to perform an accurate description of the in vitro release and in vivo performance of the 3-blades helical system.

Particle design of poorly water-soluble drug substances using supercritical fluid technologies

In order to improve the dissolution properties of poorly water-soluble drugs, some drugs were subjected to micronization or prepared as composite particles using supercritical fluid (SCF) technology with carbon dioxide (CO(2)). Solubility in CO(2) is the key when using this method. Solubility affects the supersaturation of the materials in the solvent as well as the mass transfer of that solvent, which are both critical to the micronization of the materials and the formation of the composite particles. Some useful techniques that can be used to avoid the problems posed by the characteristics of the drug itself are combining SC-CO(2) with other technologies, such as the formation of coacervates or emulsions, and other equipment types, such as milling or ultrasound fields. Another advantage of SCF technology is that it is considered to be green chemistry. SC-CO(2) can improve the solubility of poorly water-soluble drug substances using few or no organic solvents and with little or no heating.