Background: Bilastine is a non-sedating, second-generation antihistamine used to treat urticaria and allergic conjunctivitis. Objective: to formulate and test bilastine as a mucoadhesive ophthalmic in situ gel in order to extend its presence at site for longer time and help treat conjunctivitis and allergic rhinitis. Methods: We prepared formulations using different concentrations of poloxamers (Poloxamer 407 (P407) and Poloxamer 188 (P188)) in combination with hydroxypropyl methyl cellulose (HPMC). The prepared formulas were evaluated for their physicochemical properties, sol-gel transition temperature, viscosity, mucoadhesive strength, drug release, and kinetic modeling. Results: The prepared in situ gels were clear and transparent, having a pH ranging from 7.4 to 7.5 and a gelation temperature between 29.5 and 34.7 °C. Increasing the concentrations of P-407 and HPMC increased viscosity, gel strength, and mucoadhesion force, but caused a decrease in gelation temperature and drug release. Formula (F 14) containing P 407/P 188/HPMC as 19/4/0.75% w/v, respectively, exhibited favorable characteristics, including optimal gelation temperature (33°C), drug content (93%), gel strength (40 sec), mucoadhesive force (6125 dyne/cm2), and 91.4% in vitro drug release over 5 hours. Conclusions: The bilastine mucoadhesive in situ gel formulation is presented as a promising ophthalmic formulation for the treatment of allergic conjunctivitis.
