PubMed · 11366366
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1998. Norvir capsules - manufacturing problem.. https://pubmed.ncbi.nlm.nih.gov/11366366/
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The aim of this study is to use texture analysis as a non-destructive test for hard gelatin capsules filled with liquid formulations to investigate mechanical changes upon storage. A suitable amount of water in the formulations is determined to obtain the best possible compatibility with the gelatin shell. This quantity of water to be added to a formulation is called the balanced amount of water (BAW). Texture profiling was conducted on capsules filled with hydrophilic polymer mixtures and with formulations based on amphiphilic masses with high HLB value. The first model mixture consisted of polyethylene glycol 400 and polyvinylpyrrolidone K17 with water and the second type consisted of caprylocaproyl macrogol glycerides (Labrasol) with colloidal silica (Aerosil 200) and water. The liquid-fill capsules were investigated by measuring changes on mass and stiffness after storage under confined conditions in aluminium foils. Capsule stiffness was investigated also as a parameter in a response surface analysis to identify the BAW. Polyvinylpyrrolidone did not show a great influence on the BAW in the range of 10-12% (w/w) for the first model mixture. Capsules with the less hydrophilic Labrasol formulations, however, kept their initial stiffness after storage best with only half of that amount, i.e. 5-6% (w/w) of water in the compositions. From this study it can be concluded that texture profiling in the framework of an experimental design helps to find hydrophilic or amphiphilic formulations that are compatible with gelatin capsules. Short-term stability tests are meaningful if capsule embrittlement or softening is due to water equilibration or another migration process that takes place rapidly. Long-term stability tests will always be needed for a final statement of compatibility between a formulation and hard gelatin capsules.
The effect of several formulation variables on some of the physico-chemical characteristics of poly (ethyl cyanoacrylate) (PECA) nanocapsules prepared by the interfacial polymerisation of biocompatible water-in-oil microemulsions was investigated. In all cases, yields were high (>90%) and the polydispersity in size of nanocapsules was narrow. The molecular weight of the nanocapsules formed was influenced by the pH of the aqueous component of the microemulsion, increasing with increasing pH. The size of the nanocapsules formed (ranging from around 130 to 180 nm) was a function of the ratio of the mass of monomer used to the water weight fraction of the microemulsion, increasing as this ratio was increased. This is due to the formation of a thicker polymer wall resulting from the increased mass of monomer available per unit interfacial area as this ratio is increased. The rate of release of insulin from nanocapsules was also influenced by this ratio, in agreement with its effect on wall thickness. This study demonstrates that many pharmaceutically relevant physico-chemical properties of poly (alkyl cyanoacrylate) (PACA) nanocapsules prepared by interfacial polymerisation of microemulsions can readily be manipulated by changing either the pH of the aqueous component, the water weight fraction of the microemulsion or the mass of monomer used for polymerisation.
To investigate the powder plug formation process of silicified microcrystalline cellulose (SMCC) under compression forces consistent with automatic capsule-filling machines, a single-ended saw-tooth wave was used to make powder plugs with different heights (6, 8, 12 mm), at two different punch speeds (1 and 50 mm/s) on a tablet compaction simulator. SMCC was compared to Starch 1500, anhydrous lactose (direct tableting grade), and microcrystalline cellulose. Heckel analysis showed that 'apparent mean yield pressures' (AMYP) of all tested materials increased with an increase in the plug height and punch speed. AMYP appeared to depend on the material type and punch speed. Not all materials fit the Shaxby-Evans relationship at such low compression forces (less than 250 N). Only SMCC 90, SMCC HD90 and anhydrous lactose data fit the equation at both punch speeds. Due to poor axial load transmission, the R values of all tested materials decreased with an increase in the plug height. The experimental data fit the Kawakita equation quite well. Overall, Kawakita's b values were inversely related to AMYP values. The maximum breaking force (MBF) of a 12 mm plug formed at a punch speed of 50 mm/s correlated well with the work of compaction, except for SMCC HD90 and SMCC X, which exhibited very high MBF values. This research demonstrated that several grades of SMCC produced plugs having higher MBF than anhydrous lactose and Starch 1500 under similar compression conditions. The apparently higher compactability of these materials at low plug formation forces may be beneficial in developing direct fill formulations for automatic capsule filling machines.