Optimization and preparation of in-situ mucoadhesive gel of azithromycin hydroxypropyl-β-cyclodextrin inclusion complex against upper respiratory tract infections

Abstract Background Azithromycin (ATM) has limitations, such as poor oral bioavailability and gastrointestinal (GI) side effects that restrict its widespread application. Objective To develop a localized hydroxy propyl β-cyclodextrin (HP-βCD) inclusion complex-based in situ pH-responsive mucoadhesive gel of azithromycin (ATM) and evaluate its performance for the treatment of upper respiratory tract infections (URTIs). Methods According to the phase solubility diagram, the ATM HP-βCD complex was prepared and analyzed by FT-IR, DSC, and SEM. Then, using a quality-by-design approach, pH-responsive in-situ gel was prepared. It was characterized in terms of their gelling capacity, pH, spreadability, swelling index, rheological properties and antimicrobial potential. Results ATM HP- βCD complex 20-fold increased solubility of ATM, i.e., 49.84 ± 1.39 µg/mL with improved dissolution profile compared to pure ATM. Optimized formulation characterized by its gelation pH (6.7), time (1.59 min), and viscosity (1607.9 Pa.s). The developed gel showed a good spreadability index (322.6 ± 0.5%), swelling index (98.26 ± 1.54% after 10 h) and mucoadhesive strength (589 g/cm2). Also, it exhibits a sustained drug release profile for 12 h(94 ± 1.37%) and a broader zone of Staphylococcus aureus growth inhibition (31 ± 3.54 mm). Conclusion The developed mucoadhesive in situ gels demonstrated promising in vivo performance, primarily due to their effective antimicrobial activity. In vivo, local retention studies confirmed that the formulations adhered to the throat mucosa and remained in place for up to 24 h after application. The findings presented here suggested that this localized delivery system could serve as a useful strategy for improving the therapeutic effects of ATM against URTIs. Graphical Abstract