PubMed · 5952874
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M T Ho. 1966. [Some recent developments in tablets].. https://pubmed.ncbi.nlm.nih.gov/5952874/
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To obtain basic and clear release properties, wax matrix tablets were prepared from a physical mixture of drug and wax powder at a fixed mixing ratio. Properties of release from the single flat-faced surface, curved side surface, and/or whole surface of the wax matrix tablet were examined. Then tortuosity and the applicability of Higuchi's square-root time law equation were examined. The Higuchi equation well analyzed the release processes of different release manners. However, the region fitted to the Higuchi equation differed with the release manner. Tortuosity obtained with release from the single flat-faced surface and curved side surface was comparable with that obtained with the release from a reservoir device tablet, whereas tortuosity obtained with release from the whole surface was larger. As the wax matrix tablets were prepared at a fixed mixing ratio, their internal structures should be similar. Therefore changes in the matrix volume or volume fraction with release were examined, and an extra volume where dissolved drug stray becomes large with release time in the case of release from the whole surface. These factors should be taken into account for evaluation of applicability and release properties. Furthermore, the entire release process should be analyzed using a combination of the square-root time law and other suitable equations in accordance with release manner or condition.
Talc is defined as a crystalline structure characteristic of lamellar structures. Antisticking power varies according to the talc considered. Besides chemical properties, it is necessary to assess physical properties related to functionality. It is difficult to define the physical properties of talc implicated in its antisticking power. In this work, we characterized different talcs and then evaluated their performances in reducing sticking in tablet manufacturing. We compared talcs before and after delamination which is a way to obtain talcs with different physical characteristics. Granulometric analysis was carried out by laser diffractometry using a method which made it possible to assess the mean thickness of the lamellar particles. We defined a functionality assay on a single punch press to assess the antisticking power of talcs. The different talcs tested possess a very variable antisticking power towards Avicel PH 102. They present different basal dimensions and particle thickness. The force necessary to detach tablets from the punch surface varies according to the functioning time of the tablet machine, the percentage of talc and the basal dimension of talc.
The tensile strength of tablets is frequently used as a measure of the bonding achieved during compaction. Tablets from two plastically deforming materials and one brittle material have been subjected to tensile strength testing using diametral compression and three-point bending. The plastically deforming materials exhibited marked inhomogeneities, with the surfaces of the tablets considerably more compact than the inner material. The results from the two tests were different, with the three-point bending test giving higher results for tensile strength. The rate of change of tensile strength with overall tablet porosity was, however, the same for the two tests. Diametral compression would thus appear to give a reasonable estimate of bonding despite the non-homogenous nature of tablets prepared from plastically deforming materials.