Co-amorphous systems for the delivery of poorly water-soluble drugs: recent advances and an update.

INTRODUCTION: Most new drug candidates under development are poorly water-soluble, which are related to multiple pharmaceutical issues, increasing the bioavailability of these drugs by the improvement of solubility/dissolution has become a major concern to develop efficacious drugs with reasonable dosing regimens for patients. Over the past decade, increasing reports have been published on the investigation of co-amorphous drug delivery systems, with positive and excited outcomes in improving in vitro and in vivo performances of poorly water-soluble drugs. AREAS COVERED: This review summarizes recent findings of co-amorphous systems and provides their updates as a comprehensive overview in terms of classification, co-formers selection, preparation methods, physicochemical characteristics and in vivo performances. EXPERT OPINION: Co-amorphous system, a homogeneous single-phase system containing two compatible drugs or a drug with a pharmaceutically acceptable small-molecule co-former, has been employed as a promising formulation technology to improve in vitro and in vivo performances of poorly water-soluble drugs such as solubility/dissolution, stability, mechanical properties and bioavailability. Furthermore, a deeper understanding of co-amorphous systems, including its detailed classification, the criteria of co-former selection, stability mechanisms and the faced challenges as well as perspectives, will be more conducive to its development and application.