Recent Advances in Drug Delivery and Formulation - Volume 19, Issue 4, 2025

New chemical entities with low aqueous solubility and permeability encounter significant challenges in formulation development. Low solubility is further accompanied by slow dissolution and poor bioavailability, which in turn leads to unpredictability in terms of both bioavailability and toxicity. Therefore, a significant amount of exertion is necessary to enhance solubility, dissolution, and eventually bioavailability. Additionally, to enhance the solubility properties and amorphous stability of BCS Class II medications and ultimately increase drug bioavailability, co-amorphization has emerged as a promising strategy. Co-amorphous solid dispersions (CASD) are multi-component single-phase amorphous solid dispersions comprising two or more small molecules (usually known as co-formers) that might be a combination of drug-drug or drug-excipients. The selection of appropriate co-formers is critical, and the surface properties of co-amorphous formulations must be carefully evaluated, as they influence physical and chemical stability in addition to dissolution performance. Scaling up and processing co-amorphous formulations into the final dosage forms presents challenges that need to be addressed. This review will largely concentrate on the challenges, improvements, and innovations in physicochemical properties, biological characterization, and advancements of co-amorphous systems. This review will also furnish a comprehensive explanation of both established and emerging approaches utilized in the estimation of physicochemical attributes and characterization of CASD (in vitro and in vivo). Regarding CASD’s potential to improve patient outcomes and therapeutic efficacy, it has emerged as a viable approach for drug candidates posing the problems of solubility and bioavailability. This approach has also increased the physical stability of drugs.

Advanced drug delivery methods have emerged mainly because of the limitations of traditional drug delivery systems like oral and intravenous routes, along with fluctuating concentrations of drugs that have compromised therapeutic outcomes. An implantable drug delivery system (IDDS) presents an attractive alternative: long-term, continuous drug release improves therapeutic efficacy while minimizing toxicity and side effects. IDDS, first presented in the 1930s as subcutaneous hormone pellets, have gained much attention recently in drug delivery due to their controlled release of drugs in a localized and sustained manner. In systemic treatments, drugs administered through IDDS evade first-pass metabolism and enzymatic degradation within the gastrointestinal tract, therefore enhancing drug bioavailability. The most suitable properties of IDDS are its application with drugs that have poor stability or solubility in oral formulations. Even though implantation is invasive, the benefits of infrequent administration, higher patient compliance, and being able to discontinue therapy when side effects are present far outweigh the disadvantages. Today, IDDSs are used in a myriad of therapeutic areas: contraception, chemotherapy, and pain management, to name a few. Future developments in such technologies, fine-tuning these systems further, will revolutionize drug therapy by bringing even better and more patient-friendly drugs with both better efficacy and sustained periods of effects.