Many modern drugs are poorly water soluble substances, which causes difficulties in the development of solid dosage forms with sufficient bioavailability. Preparation of liquisolid systems (LSS) is a novel technique for improving solubility, dissolution and bioavailability of such drugs. The basic principle of LSS preparation is conversion of the drug in liquid state into a free-flowing, compressible, dry powder through its absorption into suitable excipients - porous carriers (aluminometasilicates, microcrystalline cellulose), subsequently coated with material having high absorption capacity (silicon dioxide commonly known as colloidal silica). LSS exhibit advantages such as lower production costs compared to soft capsules, simple processing and enhanced drug release. The main benefit is higher bioavailability of the liquid drug, caused by a large surface area available for absorption. The article tries to clarify specific aspects connected with the formulation of LSS: properties of excipients (surface area, absorption capacity), variables related to the processing (solubility, liquid load factor) and dosage form evaluation.

As coprocessed excipients (CPE) gain a lot of focus recently, this article compares three commercially available CPE of Avicel brand, namely, CE 15, DG, and HFE 102. Comparison is based on measured physical properties of coprocessed mixtures, respectively, flow properties, pycnometric density, mean particle size, specific surface area, moisture content, hygroscopicity, solubility, pH leaching, electrostatic charge, SEM images, and DSC. Tablets were made employing three pressure sets. Viscoelastic properties and ejection force were assessed during compression, as well as pycnometric density, mass uniformity, height, tensile strength, friability, disintegration, and wetting times. Avicel CE 15 is of mid-range flow properties, contains mid-size and nonspherical particles, and has high hygroscopicity, growing negative charge, best lubricity, lowest tensile strength, and mid-long disintegration times. Avicel DG possesses the worst flow properties, small asymmetrical particles, lowest hygroscopicity, stable charge, intermediate lubricity, and tensile strength and exhibits fast disintegration of tablets. Finally, Avicel HFE 102 has the best flow properties, large symmetrical particles, and middle hygroscopicity and its charge fluctuates throughout blending. It also exhibits inferior lubricity, the highest tensile strength, and slow disintegration of tablets. Generally, it is impossible to select the best CPE, as their different properties fit versatile needs of countless manufacturers and final products.

Liquisolid systems are modern formulations used to increase the bioavailability of poorly water-soluble drugs. Their preparation is based on the sorption of a drug in liquid state onto a carrier with a high adsorption capacity. The carrier particles are subsequently coated with material having a large surface area to form free-flowing powder. The main principle of bioavailability increasing is based on the presence of the dissolved drug, which is ready for immediate absorption in GI tract. Determination of capability of aluminometasilicate carrier Neusilin® US2 to adsorb different solvents. The maximum amounts of polyethylene glycol 200 (PEG 200), polyethylene glycol 400 and propylene glycol (PG), which can be sorbed by Neusilin® US2, while maintaining an acceptable flowability of the powder mixture, were evaluated using determination of the flowable liquid retention potential. From the evaluation of liquisolid powder mixtures, it could be observed that 1 g of Neusilin® US2 can retain up to 1.00 g of PG, 1.16 g of polyethylene glycol 400 and 1.48 g of PEG 200, while maintaining acceptable flowing properties. Large specific surface area in combination with a high absorption capacity makes Neusilin® US2 suitable carrier for liquisolid system preparation.

Liquisolid systems are an innovative dosage form used for enhancing dissolution rate and improvingin vivobioavailability of poorly soluble drugs. These formulations require specific evaluation methods for their quality assurance (e.g., evaluation of angle of slide, contact angle, or water absorption ratio). The presented study is focused on the preparation, modernin vitrotesting, and evaluation of differences of liquisolid systems containing varying amounts of a drug in liquid state (polyethylene glycol 400 solution of rosuvastatin) in relation to an aluminometasilicate carrier (Neusilin US2). Liquisolid powders used for the formulation of final tablets were prepared using two different methods: simple blending and spraying of drug solution onto a carrier in fluid bed equipment. The obtained results imply that the amount of liquid phase in relation to carrier material had an effect on the hardness, friability, and disintegration of tablets, as well as their height. The use of spraying technique enhanced flow properties of the prepared mixtures, increased hardness values, decreased friability, and improved homogeneity of the final dosage form.