Most of the newly developed drugs are hydrophobic and therefore poorly soluble in water, which leads to slow drug absorption and inadequate bioavailability. Lipid-based systems have great potential due to their ability to improve water solubility and bioavailability of drugs. Self-microemulsifying drug delivery systems (SMEDDS) have a droplet size < 100 nm and improve bioavailability of orally administered hydrophobic drugs. The drug is already in dissolved form, thus avoiding the dissolution process, which is key limiting factor in the absorption of drugs belonging to BCS class II (poor solubility, good permeability).
The purpose of our Master's thesis was to convert liquid SMEDDS with poorly water-soluble drug (carvedilol) into solid formulation (granules) by wet granulation. The proportion of binder and the type of binder (povidone K30, povidone K90, copovidone) in the granulation liquid ((micro)emulsion SMEDDS/water = 70/30) were varied and studied. Mesoporous silicon dioxide Syloid® 244FP was used as a carrier. We managed to incorporate a large amount of SMEDDS into the carrier in hand-made granules (in mortar), as SMEDDS represented about 60 % of the final granules. The produced granules had good flow properties and by photon correlation spectroscopy we proved, that the granules have preserved self-microemulsifying abilities. Granules with best flow properties were evaluated for release in acidic medium with pH 1.2 and phosphate buffer with pH 6.8, where we found that the binder povidone K30 has a beneficial effect on the release of granules compared to those without binder, povidone K90 due to higher molecular weight slows down release, while copovidone has no significant effect on release.
The best granules with 1,85% povidone K30 were also produced in a high-shear mixer and those granules were then compressed into tablets. We managed to make tablets containing 25 % of granules. Tablets successfully passed the friability test (0,22 %, requirement < 1 %) and the disintegration test (50-55 s, requirement < 15 min). The release of drug from tablets was slightly slower in comparison to the release from granules, which was undesirable but also expected. During compression SMEDDS penetrated deeper into the pores of the carrier and as a result drug is released more slowly. In addition, tablets must first disintegrate in order for the drug to be released.
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