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Pellet formulations as represented by multiparticulate systems are often contained in hard capsules. We examined the use of a different approach to the making of compressed tablets containing pellets, OSDRC-technology. OSDRC-technology employs a double-structure punch (center punch and outer punch) allowing for dry-coated tablets to be assembled in a single run. We examined the effects of the thickness of the outer punch, formability of pellets, and diameter of tablets on pellet filling. The results revealed that thinner outer punches are not always better for filling small tablets with large amounts of pellets. We considered that this was because the core pellets spread in a cone shape within the formulating tablets at filling, requiring a thickness of the outer punch and a particle density of the diluents at which pellets would not exude from the formulating tablets. It was suggested that the formability of core pellets affects the maximum number of layers of pellets, and higher formability would yield better results. However, we found that pellets with poor formability (tensile strength ofor =2 kPa) could be used in tablets. For the tablets, the larger the diameter, the greater the maximum number of layers. We considered this to be due to the friction between the pellets and punch wall. We concluded that OSDRC-technology could be applied to capsule-like forms containing pelletsor =50 wt% through an unconventional approach.

This study was conducted in order to clarify the compression characteristics, and to confirm the superiority of the physical properties, of the newly invented One-Step DRy-Coated tablets (OSDRC). We compared both the compression characteristics and the physical properties of OSDRC with those of physical-mixture tablets (PM) that were prepared with the same ingredients, quantity, and compression pressures. We selected potassium chloride (KCl) and acetaminophen (AAP) as the model drugs, since the former is known for its appropriate compression characteristics and the latter for its brittleness. The advantage of OSDRC is that they are capable of maintaining any kind of drug in their core, because the core is tightly surrounded by the outer layer, even when the drugs in the core have poor compression characteristics, which causes difficulties in forming a solid core tablet using conventional dry-coated tablet methods. The radial tensile strength of OSDRC was the same as, or superior to, that of PM containing of AAP. The results were in accordance with the compression process analysis performed according to Kawakita's equation. The friability of OSDRC was also superior to that of PM. These preferable characteristics were attributable to the high intensity of the OSDRC outer layer surface in comparison to that of PM. It was difficult to clarify the difference between OSDRC and PM in their physical properties when KCl was applied, since the tabletability of the whole tablet was high due to KCl's physical properties. The OSDRC containing AAP in their cores showed a controlled release pattern, though no other materials that have been known to influence drug release was present. It was considered that this controlled release pattern was caused by a reduced AAP particle surface area due to compression. It was confirmed with these experiments that the compression characteristics and the physical properties of AAP-OSDRC were superior to those of PM. These results indicated that it is possible to produce tablets that have materials with poor compression characteristics in the core portion, and high tabletability materials for the outer layers. In other words, it is possible to produce capsule-like tablets using the OSDRC compression method.

A novel method of manufacturing one-step dry-coated (OSDRC) tablets, which we recently invented, was used to produce sugar-coated tablets protected from moisture without the need for a conventional complicated sugar coating process. Amorphous sucrose was selected for the outer layer of the OSDRC tablets as sugar-coated layer. The isothermal crystallization behavior and characteristics such as water vapor permeability, tensile strength, and disintegration time of compressed amorphous sucrose were investigated. Water vapor adsorption measurements showed the crystallization behavior of amorphous tablets to be similar to that of amorphous powder, although it was affected by compression pressure. We found that the crystallized amorphous sucrose after compression at 200 MPa was moisture protective, and the water vapor permeability coefficient was decreased to 1/2000 or less compared with a tablet prepared with a lactose-microcrystalline cellulose (MCC) mixture, hydroxypropylmethylcellulose (HPMC), and sucrose crystal. The water vapor permeability and physicochemical characteristics were influenced by the amorphous content or additive content. It was confirmed that a new sugar-coated tablet using amorphous sucrose and OSDRC technology was moisture protective, therefore, it was concluded that the novel sugar coating method was very useful to obtain a moisture protective tablet.

One-step dry-coated tablets (OSDRC) were prepared using materials which are generally used in pharmaceutical tablets. The radial tensile strength of OSDRC was measured for various compression pressures and core porosities before the final compression to compare with that of conventional dry-coated tablets (DC). Furthermore, stress relaxation in the compression process was investigated. Radial tensile strength and stress relaxation profiles of OSDRC were the same as those of conventional DC. X-ray computerized tomography (CT) of the tablets showed that the density distribution of both tablets was also the same. Thus, we concluded that OSDRC and conventional DC have the same compression characteristics and physical properties. The OSDRC-system was executed by the use of upper and lower punches, which had a double structure, a center punch, and an outer punch surrounding the center punch. The OSDRC process consists of three compressions to make the lower-outer layer (1st-outer layer), the core, and the whole tablet including the upper-outer and side-outer layers (2nd-outer layer). At first, the powder for the 1st-outer layer fills a space, which is made by the lower-center punch and lower-outer punch, and is pre-compressed by the upper-center punch. Then, while the upper-center punch pushes the pre-compressed 1st-outer layer, the lower-center punch is slid down. The upper-center punch is then pulled away to make a space, which is filled with the powder for the core. This is then pre-compressed by the upper-center punch. Finally, the lower-outer punch is slid downward and the powder for the 2nd-outer layer fills and surrounds the pre-compressed core/1st-outer layer completely. The core/1st-outer layer and the 2nd-outer layer complex is then compressed by the upper and lower punches in which the center punches are unified with the outer punches, respectively. This system can be assembled onto the turn table of a rotary tableting machine, and can make a dry-coated tablet in a single turn.