PubMed · 13238813
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R D AZULAY. 1955. [Topical therapy; current trend].. https://pubmed.ncbi.nlm.nih.gov/13238813/
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The modification of a twin screw extruder for continuous wet granulation was investigated. Modification of the extruder setup as well as the screw design allowed the continuous wet granulation of alpha-lactose monohydrate without the need of a wet sieving step. The robustness of twin screw granulation was evaluated by studying the influence of processing parameters and formulation variables on the process performance and on the properties of alpha-lactose monohydrate granules and tablets. The process reproducibility during long term production was evaluated. Screw speed (200-450 rpm) and total input rate (5.5-9.5 kg/h) had no significant influence on the granule properties, while the water concentration during granulation influenced the process as well as the granule properties. At a water concentration (calculated on wet granule basis) of 5.5-8.5%, continuous twin screw granulation of alpha-lactose monohydrate 200 M was feasible and the granules obtained had good properties. PVP addition mainly affected tablet properties. Tablets made from granules containing 2.5% PVP had a tensile strength above 0.94 MPa, a friability below 1% and a disintegration time ranging between 495 and 576 s. Tablets containing hydrochlorothiazide complied with the dissolution requirements as 60% was released after 5 and 15 min from tablets without PVP and with 2.5% PVP, respectively. No problems were observed during continuous twin screw granulation over a period of 8h and the granule and tablet properties were reproducible throughout the process. These results indicated that twin screw granulation is an efficient tool for continuous wet granulation.
A study was performed in order to elucidate the effects of powder particle size and binder viscosity on intergranular and intragranular particle size heterogeneities. Granules were produced by melt granulation in a high shear mixer from each of four calcium carbonates having mean particle sizes in the range of 5.5-63.1 microm. Each of three polyethylene glycols (PEGs) having viscosities in the range of approximately 40-14,000 mPas were applied as meltable binders. The size distribution of the calcium carbonate particles in three granule size fractions (125-250, 355-500, and 800-1000 microm) was measured after disintegration of the granules. Intragranular particle size heterogeneities were evaluated qualitatively by means of scanning electron microscopy. A preferential growth of the smaller particles was found to give rise to a higher content of small particles in large granules when calcium carbonates with mean particle sizes of 11.7, 34.5, and 63.1 microm were granulated with a binder of low viscosity. The use of a binder of medium or high viscosity leads to a marked reduction of these heterogeneities. A preferential growth of larger particles was seen when calcium carbonates with mean particle sizes of 5.5 and 11.7 microm were granulated with a highly viscous binder. The use of a binder with low or medium viscosity resulted in an increased homogeneity. Intragranular particle size heterogeneities were primarily seen when 5.5 and 11.7 microm calcium carbonate particles were granulated with a highly viscous binder.
The aim of the study was to analyze very differently deforming materials using 3D parameter plots and consequently to gain deeper insights into the densification and deformation process described with the 3D model in order to define an ideal tableting excipient. The excipients used were dicalcium phosphate dihydrate (DCPD), sodium chloride (NaCl), microcrystalline cellulose (MCC), xylitol, mannitol, alpha-lactose monohydrate, maltose, hydroxypropyl methylcellulose (HPMC), sodium carboxymethylcellulose (NaCMC), cellulose acetate (CAC), maize starch, potato starch, pregelatinized starch, and maltodextrine. All of the materials were tableted to graded maximum relative densities (rhorel, max) using an eccentric tableting machine. The data which resulted, namely force, displacement, and time, were analyzed by the application of 3D modeling. Different particle size fractions of DCPD, CAC, and MCC were analyzed in addition. Brittle deforming materials such as DCPD exhibited a completely different 3D parameter plot, with low time plasticity, d, and low pressure plasticity, e, and a strong decrease in omega values when densification increased, in contrast to the plastically deforming MCC, which had much higher d, e, and omega values. e and omega values changed only slightly when densification increased for MCC. NaCl showed less of a decrease in omega values than DCPD did, and the d and e values were between those of MCC and DCPD. The sugar alcohols, xylitol and mannitol, behaved in a similar fashion to sodium chloride. This is also valid for the crystalline sugars, alpha-lactose monohydrate, and maltose. However, the sugars are more brittle than the sugar alcohols. The cellulose derivatives, HPMC, NaCMC, and CAC, are as plastic as MCC, however, their elasticity depends on substitution indicated by lower (more elastic) or higher (less elastic) omega values. The native starches, maize starch and potato starch, are very elastic, and pregelatinized starch and maltodextrine are less elastic and exhibited higher omega values. Deformation behavior as shown in 3D parameter plots depends on particle size for polymers such as CAC and MCC; however, it does not depend on particle size for brittle materials such as DCPD. An ideally deforming tableting excipient should exhibit high e, d, and omega values with a constant ratio of e and omega at increasing densification.