**1. Introduction**

The challenge of modern pharmaceutical technology is designing easy-to-administer drug dosage forms where the dose is su fficiently flexible to enable proper application and dose titration both to paediatric and adult patients. The currently available formulations that might be used in any age population are primarily liquids. However, the barrier of their utilization are di fficulties in effective taste masking of bitter active pharmaceutical ingredients (API), the necessity of applying a large volume of medical preparation to adults, as well as low physicochemical and microbiological

stability. Therefore, new technological solutions and strategies are being sought, as the appropriate drug formulation should be acceptable for a wide age group, in terms of organoleptic properties (taste, smell, appearance) to ensure regular intake of medicine, even while prolonged therapy. In case of solids, a crucial element that decides if they are swallowed, is their size—the smaller the unit, the easier application [1–4].

The solid drug dosage form, which connects the advantages of liquids (flexibility of dosing, ease of swallowing) with the qualities of solids (taste masking, stability), as well as enables individual dose adjustments for patients of all ages are minitablets (MT). MT are created for those encountering di fficulties with application of larger tablets or as a form providing the possibility of dose titration by "multiplication", which allows the use of one product for the entire age population. The appropriate dose is determined by the number of MT administered (e.g., children of di fferent ages will take di fferent number of MT as one dose). MT are characterized by small sizes of one to three millimeters and mass of 5–25 mg. They are produced like traditional tablets, using existing technologies and production lines, as well as standard tableting blends. A promising type of MT are orodispersible minitablets (ODMT), which are characterized by very short disintegration and dissolution rates. ODMT are particularly recommended for patients with swallowing problems, by eliminating the risk of choking to a minimal [5–11].

The major limitation in designing orodispersible formulations is unpleasant taste of API. Insu fficient taste masking e ffect of medicine is the most common reason for refusing of taking the preparation [12]. Taste masking techniques can be divided in two main groups: chemical modifications of API to reduce its solubility or creating a physical barrier between drug molecules and taste receptors. The first group includes primarily conversion into a prodrug (ester, salt), complexation with cyclodextrins, or ion exchange resins. The second mechanism involves designing microparticles or coatings using polymers having limited solubility in the oral cavity environment. A useful method of decreasing unsavory taste of a medicine is obtaining microparticles utilizing taste masking polymers. There are several technologies for preparing microparticles, among which spray drying is one of the most e ffective and e fficient [12–16].

The aim of the following paper was to create ODMT containing microparticles with rupatadine fumarate (RUP) as a model bitter drug. Microparticles were obtained employing the spray-drying, utilizing ethylcellulose as a barrier forming polymer. In our previous work, microparticles prepared using di fferent forms of EC were compared. The microparticles prepared with an aqueous dispersion of EC were found to have better properties in terms of taste masking e ffectiveness and morphology [17], therefore they were used to formulate ODMT. ODMT were evaluated regarding their morphological structure utilizing scanning electron microscopy (SEM), uniformity of weight and thickness, mechanical properties, drug content, and potential interactions occurring using di fferential scanning calorymetry. Disintegration time was evaluated in vivo by healthy volunteers on petri dishes and with texture analyzer usage. The crucial test—assessment of taste masking e ffect was carried out according to three alternative approaches: in vivo, by the drug dissolution and with electronic tongue utilization.

#### **2. Materials and Methods**
