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PurposeThe formulation of topical ophthalmic products with appropriate therapeutic effect and patient compliance is a major challenge. To increase the efficiency of the ocular delivery of the drug, the enhancement of water solubility and the contact time of the drug on the surface of the cornea are necessary. In this work, prednisolone (PR)-containing eye drops were formulated with antimicrobial, mucoadhesive biopolymer and PR–cyclodextrin inclusion complex. This approach can be used for the development of innovative ophthalmic formulations.Materials and methodsAfter adjusting the optimal physiological parameters, the amount of the required cyclodextrin for the highest penetration of PR was determined by dialysis membrane diffusion study. The viscosity, surface tension and mucoadhesion of the eye drops were measured. The microbiological effectiveness of zinc-hyaluronate (ZnHA) was investigated by a standard method of the European Pharmacopoeia.ResultsIn this case, no significant difference of surface tension was measured in products with different amounts of cyclodextrin. According to the results of the tensile test, ZnHA as a mucoadhesive biopolymer improves the mucoadhesion of ophthalmic products. The antimicrobial stability of formulations preserved by ZnHA meets requirement B of the European Pharmacopoeia.ConclusionIt can be stated that the innovative PR-containing compositions are suitable for producing mucoadhesive, properly preserved aqueous ophthalmic solutions with increased bioavailability attributes.

Production of spherical crystals with an appropriate particle size is an important objective for active agents dedicated to direct tablet making (Nat. Mater.201110867871; Cryst. Growth Des.20151551495156). The material chosen for our experiments, ambroxol hydrochloride, is such a solid compound. The optimal habit for the crystals of direct compressible active agents and additives includes sphericity, proper mean particle size, and appropriate surface. The main objective of the present work is to compare typical and nontypical spherical crystallization methods and to investigate their applicability for ambroxol hydrochloride. The particles were investigated by light microscopy, coupled with an image analyzator program, scanning electron microscopy, powder X-ray diffractometry and differential scanning calorimetry in order to obtain information about particle morphology, mean particle size, aspect ratio, roundness and potential polymorphic transitions. Powder rheology properties were also investigated. The typical crystallization method of quasi-emulsion solvent diffusion was suitable for increasing mean particle size, but large-size spherical crystals did not form. Nontypical spherical crystallization methods (spherical agglomeration and the method of cooling with an alternating temperature profile) caused an increase in mean particle size and an improvement in aspect ratio and roundness. Powder rheology parameters of the spherical agglomeration products improved, too.