Nasal drug delivery is well estabilshed in the treatment of local nasal mucosa diseases. It is also being investigated as an alternative route of systemic drug delivery, as well as the possibility of direct drug delivery to the central nervous system. Limitations of nasal drug administration include difficult drug delivery to the target area and mucociliary clearance, which shortens the contact time between the drug and the nasal mucosa. Nasal use of corticosteroids is common in the treatment of diseases of the nasal mucosa and paranasal sinuse. Recently it has been suggested in the treatment of neuroinflammatory processes. Within this doctoral thesis, employing quality by design principles, three innovative in situ gelling pharmaceutical forms of corticosteroid for nasal spray application have been developed: (i) in situ gelling microsuspension of fluticasone propionate (FP), (ii) in situ gelling nanosuspension of FP prepared by wet media milling; and (iii) powder platform consisting of dexamethasone sodium phosphate (DSP)-loaded microspheres blended with an inert carrier. Thorough physicochemical and biopharmaceutical characterization of developed systems was performed. The polymer composition of the in situ gelling micro- and nanosuspensions of FP ensured shear thinning behavior, suitability for administration as a spray (i.e., suitable droplet size and spray angle), and immediate gelling in contact with simulated nasal fluid (SNF). Microspheres with DSP, prepared by spray drying, are characterized by high drug entrapment efficiency, adequate residual moisture content, and good swelling ability in SNF, forming a gel. Blends of microspheres with DSP and inert carrier were homogeneous and had better flow properties and a narrower spray cone angle than the microspheres alone. Successful deposition of all three pharmaceutical forms in the target region of the nasal cavity model was achieved, depending on the desired effect. Developed pharmaceutical forms are characterized by better mucoadhesiveness compared to conventional forms. Drug release from all developed forms was suitable for nasal administration. Nanonization of FP resulted in greater mucoadhesiveness of the formulation and increased solubility and release rate of FP from the in situ gel, providing the possibility of reducing the applied dose. Biocompatibility on the in vitro Calu-3 cell model and the physicochemical stability was confirmed for all developed formulations. The powder system with DSP showed the potential to improve drug permeation through the nasal epithelium. By varying process, formulation and/or administration parameters, employing design of experiments, innovative pharmaceutical forms of corticosteroids with the potential for prolonged retention at the site of administration, favourable biopharmaceutical properties and optimized deposition in the nasal cavity have been successfully developed.