Supercritical Antisolvent Versus Coevaporation— Preparation and Characterization of Solid Dispersions

Particle preparation of pharmaceutical compounds using supercritical antisolvent process: current status and future perspectives

The low aqueous solubility and subsequently slow dissolution rate, as well as the poor bioavailability of several active pharmaceutical ingredients (APIs), are major challenges in the pharmaceutical industry. In this review, the particle engineering approaches using supercritical carbon dioxide (SC CO₂) as an antisolvent are critically reviewed. The different SC CO₂-based antisolvent processes, such as the gas antisolvent process (GAS), supercritical antisolvent process (SAS), and a solution-enhanced dispersion system (SEDS), are described. The effect of process parameters such as temperature, pressure, solute concentration, nozzle diameter, SC CO₂ flow rate, solvent type, and solution flow rate on the average particle size, particle size distribution, and particle morphology is discussed from the fundamental perspective of the SAS process. The applications of the SAS process in different formulation approaches such as solid dispersion, polymorphs, cocrystallization, inclusion complexation, and encapsulation to enhance the dissolution rate, solubility, and bioavailability are critically reviewed. This review highlights some areas where the SAS process has not been adequately explored yet. This review will be helpful to researchers working in this area or planning to explore SAS process to particle engineering approaches to tackle the challenge of low solubility and subsequently slow dissolution rate and poor bioavailability.

Strategies to address low drug solubility in discovery and development

Drugs with low water solubility are predisposed to low and variable oral bioavailability and, therefore, to variability in clinical response. Despite significant efforts to "design in" acceptable developability properties (including aqueous solubility) during lead optimization, approximately 40% of currently marketed compounds and most current drug development candidates remain poorly water-soluble. The fact that so many drug candidates of this type are advanced into development and clinical assessment is testament to an increasingly sophisticated understanding of the approaches that can be taken to promote apparent solubility in the gastrointestinal tract and to support drug exposure after oral administration. Here we provide a detailed commentary on the major challenges to the progression of a poorly water-soluble lead or development candidate and review the approaches and strategies that can be taken to facilitate compound progression. In particular, we address the fundamental principles that underpin the use of strategies, including pH adjustment and salt-form selection, polymorphs, cocrystals, cosolvents, surfactants, cyclodextrins, particle size reduction, amorphous solid dispersions, and lipid-based formulations. In each case, the theoretical basis for utility is described along with a detailed review of recent advances in the field. The article provides an integrated and contemporary discussion of current approaches to solubility and dissolution enhancement but has been deliberately structured as a series of stand-alone sections to allow also directed access to a specific technology (e.g., solid dispersions, lipid-based formulations, or salt forms) where required.

Characterization of solid dispersions of itraconazole and vitamin E TPGS prepared by microwave technology

Background: This study describes the influence of microwave irradiation (MW) on the preparation and properties of solvent-free solid dispersions (SDs) employing vitamin E D-α-tocopheryl polyethylene glycol (TPGS) 1000 succinate, with itraconazole as a model drug. Materials and methods: Itraconazole is characterized by low aqueous solubility and vitamin E TPGS was chosen as the surfactant carrier for the formulation of MW solid dispersions in different ratios. Their physicochemical characteristics were investigated by means of powder x-ray diffraction (PXRD), differential scanning calorimetry (DSC), diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy and hot-stage microscopy. Comparison with the corresponding physical mixtures and the drug alone allowed the relationship between influence of the technological process on physicochemical and morphological properties of the systems to be examined. Results: PXRD data confirmed the absence of phase transitions in the solid state of the drug subjected to MW alone. On the other hand, an amorphous form of the drug was obtained in the solid dispersion with the highest content of carrier investigated (1:3 w/w). All the SDs showed an improvement in the solubility and dissolution profile of the drug, with the best results obtained in the case of the 1:3 w/w SD. This was related to an interaction between the drug and the carrier with a complex that formed due to favorable H bonds, as demonstrated by DRIFT analysis. Conclusion: It was demonstrated that the amorphization of the drug led to an increase in wettability and a significant improvement in bioavailability. Therefore, SDs obtained by MW technique using vitamin E TPGS as carrier provide a promising way to increase the dissolution rate and solubility of poorly bioavailable drugs.