A Novel Desloratadine-Benzoic Acid Co-Amorphous Solid: Preparation, Characterization, and Stability Evaluation

Low physical stability is the limitation of the widespread use of amorphous drugs. The co-amorphous drug system is a new and emerging method for preparing a stable amorphous form. Co-amorphous is a single-phase amorphous multicomponent system consisting of two or more small molecules that are a combination of drugs or drugs and excipients. The co-amorphous system that uses benzoic acid (BA) as an excipient was studied to improve the physical stability, dissolution, and solubility of desloratadine (DES). In this study, the co-amorphous formation of DES and BA (DES⁻BA) was prepared by melt-quenching method and characterized by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), powder X-ray diffraction (PXRD), and polarized light microscopy (PLM). Dissolution, solubility, and physical stability profiles of DES⁻BA were determined. The DES crystals were converted into DES⁻BA co-amorphous form to reveal the molecular interactions between DES and BA. Solid-state analysis proved that the co-amorphous DES⁻BA system (1:1) is amorphous and homogeneous. The DSC experiment showed that the glass transition temperature (Tg) of tested DES⁻BA co-amorphous had a higher single Tg compared to the amorphous DES. FTIR revealed strong interactions, especially salt formation. The dissolution rate and solubility of co-amorphous DES⁻BA (1:1) obtained were larger than the DES in crystalline form. The PXRD technique was used to assess physical stability for three months at 40 °C with 75% RH. The DES⁻BA co-amorphous system demonstrated better physical stability than a single form of amorphous DES. Co-amorphous DES⁻BA has demonstrated the potential for improving solid-state stability, as the formation of DES⁻BA co-amorphous salt increased solubility and dissolution when compared to pure crystalline DES. This study also demonstrated the possibility for developing a DES⁻BA co-amorphous system toward oral formulations to improve DES solubility and bioavailability.