In recent years there has been a growing interest in formulating solid dispersions, which purposes mainly include solubility enhancement, sustained drug release and taste masking. The most notable problem by these dispersions is drug-carrier (in)solubility. Here we focus on solubility parameters as a tool for predicting the solubility of a drug in certain carriers. Solubility parameters were determined in two different ways: solely by using calculation methods, and by experimental approaches. Six different calculation methods were applied in order to calculate the solubility parameters of the drug ibuprofen and several excipients. However, we were not able to do so in the case of ibuprofen lysinate, as calculation models for salts are still not defined. Therefore, the extended Hansen’s approach and inverse gas chromatography (IGC) were used for evaluating of solubility parameters for ibuprofen lysinate. The obtained values of the total solubility parameter did not differ much between the two methods: by the extended Hansen’s approach it was δt = 31.15 MPa^0.5 and with IGC it was δ_t = 35.17 MPa^0.5. However, the values of partial solubility parameters, i.e., δ_d, δ_p and δ_h, did differ from each other, what might be due to the complex behaviour of a salt in the presence of various solvents.

Paracetamol (PAR) crystals exhibit poor compressibility, poor flowability and its tablets show a tendency to cap. To improve the mechanical strength of tablets several kinds of “Paracetamol for direct compression” are present on the market. Current research demonstrated the best tablet properties with coated paracetamol (mass of tablets, diameter, height and mechanical strength, friability RSD<2%). Furthermore, coated paracetamol in combination with both investigated superdisintegrants such as Vivasol®and Polyplasdone® XL-10 shows faster disintegration time and dissolution rate in comparison to paracetamol for direct compression. Eventually, the major advantages of the formulation with coated paracetamol for industrial production are decrease of friability and superiority in terms of flowability, compressibility, quick disintegration and dissolution. Regarding the results, coating of PAR particles is beneficial for the manufacturing of tablets with immediate release. Key words: Paracetamol, powder, direct compression, immediate release, superdisintegrants.

Indomethacin is a widely used anti-inflammatory drug with serious side-effects. This drug was used as a model drug for the coating of agglomerates with a permeable film (Eudragit NE). The agglomeration of the crystals increased the flowability of the bulk crystals. The coating further improved the flowability, and also the uniformity of the mass of the filled capsules. The coating film also influenced the wetting of the samples. The coating decreased the surface free energy and therefore reduced the adhesion forces between both the dry and the wet particles. The modification of the flow properties and the even capsule filling can be explained by this phenomenon. Since coating film does not dissolve in the artificial gastric juice, the dissolution test was performed only in the artificial intestinal juice. The dissolution of indomethacin from the coated sample was changed significantly. Accordingly, coating of the crystals can be performed in order to protect the mucosa of the gastrointestinal tract or to promote the preparation of solid dosage form.