As a large proportion of newly discovered active pharmaceutical ingrediants (API) belong to II. and IV. class of the biopharmaceutical classification system and show poor solubility in aqueous media, increasing solubility is one of the major challenges in pharmaceutical development. Approaches to improving solubility also include lipid-based systems, including self-microemulsifying drug delivery systems (SMEDDS). These are composed of lipids, surfactants and co-solvents. They are characterized by the spontaneous formation of an oil-in-water microemulsion after dilution in an aqueous medium, which helps to increase the solubility of the active substance and, consequently, to improve absorption and higher bioavailability.
Many API’s are in the gastrointestinal tract (GIT) subject to precipitation, so during the experimental work we investigated how the use of various precipitation inhibitors inhibits precipitation in order to keep API in the dissolution medium in dissolved form. Thus, we first prepared a liquid SMEDDS with the model active ingredient carvedilol and with the addition of different precipitation inhibitors (Pharmacoat® 606, PVP K30 and Soluplus®) in different concentrations, we monitored the release profile and the time when API precipitation occurs. We have proven that using precipitation inhibitors is very effective in inhibiting the process of precipitation of API.
Because solid pharmaceutical forms have many advantages over liquid ones (stability, easier and cheaper production), we have converted liquid SMEDDS into a solid form by wet granulation in a paten. Mesoporous carriers Syloid® 244 FP and Neusilin® US2 were used. The flow properties, size, size distribution and release profile were evaluated with the produced granules. The best formulation according to the mentioned properties was granulated in a high-shear mixer and these granules were compared with hand-made granules. When converting to a solid form, it is very important that the formulation retains its self-microemulsifying properties, which was also verified and confirmed by photon correlation spectroscopy.
|