Formulation of olopatadine hydrochloride viscous eye drops – physicochemical, biopharmaceutical and efficacy assessment using in vitro and in vivo approaches

•Formulation and evaluation of olopatadine viscous eye drops was performed.•Combination of chitosan and hydroxypropyl guar gum was compatible with the drug.•The drug permeability was estimated using HCE-T cell-based models and PAMPA.•MTT assay demonstrated that the tested eye drops were non-toxic and well tolerated.•An ocular itch test on mice was employed for efficacy evaluation.