Recent Progress in Formulation Approaches for Improving the Solubility and Bioavailability of Poorly Soluble Drugs

Dear Colleagues,

The rise in the number of poorly soluble drugs over last several years has forced the pharmaceutical industry towards the development of formulation approaches for improving the solubility and bioavailability of these drugs. Although several decades have passed since the introduction of solid dispersion technology and other conventional formulation approaches (e.g., complexation with cyclodextrins; the use of salts, cosolvents, surfactants, and prodrugs), there is still a huge number of potential drugs with proved pharmacological activity that do not reach market due to undesired physicochemical and biopharmaceutical properties. Several problems hinder the market appearance of these formulations, such as inherent limitations of preparation techniques (the use of organic solvents or elevated temperatures), poor flowability and compressibility behavior of the obtained product, stability issues due to drug recrystallization from amorphous form or polymorphic transitions, as well as high formulation bulk caused by the high weight percentage of excipient required to ensure formulation stability. Several market withdrawals in the past few years caused by drug recrystallization and consequently changes in drug dissolution could probably have been avoided if more efforts were invested in understanding the physicochemical characteristics of drug–excipient systems by both analytical and molecular modelling techniques. Significant progress has been made during the last several years in this area, including the development of novel preparation techniques such as KinetiSol^® dispersion, supercritical fluid processing, cryogenic processing, electrospinning, etc.; the application of formulation approaches which enable higher drug loading (e.g., nanocrystals or co-amorphous systems); as well as the use of advanced methods for physicochemical characterization. The introduction of molecular modelling and simulation tools and thermodynamic modelling in formulation development made possible the simulation of interactions between drugs and other formulation components on the molecular level and the elucidation of system physicochemical properties and potential stability issues. This should facilitate the achievement of the ultimate goal of developing formulations without stability concerns, which is a prerequisite to enter the market.

Therefore, both original and review papers focused on novel findings in formulation approaches for improving solubility and bioavailability of poorly soluble drugs—particularly solid dispersions, co-amorphous systems, and nanocrystals—are welcome in this Special issue. Submitted papers should address aspects of process optimization, elucidation of mechanisms responsible for drug amorphization and stabilization of the amorphous form, the application of molecular modelling and simulation tools in formulation development, downstream formulation processing into dosage forms suitable for the market, and the evaluation of bioavailability improvement through in vivo animal studies or in silico PBPK modelling.  

Prof. Dr. Kyriakos Kachrimanis
Dr. Djordje Medarevic
Guest Editors

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