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The aim of this study was to evaluate the potential of a cross-linked pregelatinized potato starch (PREGEFLO® PI10) as matrix former for controlled release tablets. Different types of tablets loaded with diprophylline, diltiazem HCl or theophylline were prepared by direct compression of binary drug/polymer blends. The drug content was varied from 20 to 50%. Two hydroxypropyl methylcellulose grades (HPMC K100LV and K100M) were studied as alternative matrix formers. Drug release was measured in a variety of release media using different types of experimental set-ups. This includes 0.1 N HCl, phosphate buffer pH 6.8 and water, optionally containing different amounts of NaCl, sucrose, ethanol or pancreatin, fasted state simulated gastric fluid, fed state simulated gastric fluid, fasted state simulated intestinal fluid, fed state simulated intestinal fluid as well as media simulating the conditions in the colon of healthy subjects and patients suffering from Crohn's disease. The USP apparatuses I/II/III were used under a range of operating conditions and optionally coupled with the simulation of additional mechanical stress. Importantly, the drug release kinetics was not substantially affected by the investigated environmental conditions from tablets based on the cross-linked pregelatinized potato starch, similar to HPMC tablets. However, in contrast to the latter, the starch-based tablets roughly kept their shape upon exposure to the release media (they "only" increased in size) during the observation period, and the water penetration into the systems was much less pronounced. Thus, the investigated cross-linked pregelatinized potato starch offers an interesting potential as matrix former in controlled release tablets.

Different types of starches were used to prepare controlled release tablets loaded with diprophylline by direct compression. The impact of the natural origin of the starch, potential chemical modifications (e.g., cross-linking with phosphate or adipate, hydroxypropylation, acetylation to different degrees, partial hydrolysis) and type of pre-gelatinization process (laboratory scale with ethanol and oven drying versus industrial scale drum drying) on the resulting drug release kinetics were studied. Texture analysis of the hydrogels created upon exposure to the release medium, optical and scanning electron microscopy as well as X-ray powder diffraction measurements were used to better understand the observations. Also, a “quick test” using a texture analyzer to rapidly estimate the capacity of a specific starch type to control the resulting drug release rate was proposed. Two types of hydroxypropyl methylcellulose (HPMC K100 M and K100 LV) were studied for reasons of comparison. Interestingly, the “quick test” allowed to detect differences in the mechanical strength of the hydrogels formed upon contact with aqueous fluids, which correlated well with the observed drug release patterns from tablets when measured using a USP III (“Bio’-Dis”) apparatus at 30 rpm. However, diprophylline release was not very much affected by the investigated starch types when using a USP basket apparatus at 75 rpm. This can be attributed to the much lower mechanical stress experienced by the hydrogels under these conditions. Furthermore, caution must be paid when studying starch types, which are pre-gelatinized at the laboratory scale using ethanol precipitation and oven drying. The obtained starch granules can have significantly different key properties compared to granules obtained by industrial scale drum drying, resulting in substantially different drug release patterns.

This article highlights the use of a novel easy to use uniaxial force displacement tester (FDT) for measuring powder cake strength. A comparative study was undertaken of the FDT with a standard ring shear tester (RST) for measuring the cake strength of a powder. The powder used in the study was maltodextrin DE 21 which is an amorphous powder which readily cakes at temperatures at or above its glass transition. The powder was first equilibrated at 50% relative humidity over a five month period and it was then exposed to temperatures at and above its glass transition. The powder cake strength was measured using both the FDT and RST and the measured results were compared. The results showed that the cake strengths measured by the FDT correlated well with those of the RST. This demonstrated that the FDT is a realistic, easy to use method for assessing the cake strength of a powder.

This work examined and compared the caking behaviour of three physically and chemically different food powders. The food powders studied were maltodextrin DE21 which is an amorphous powder, common salt which consists of crystalline NaCl, and skim milk powder (SMP) which contains a mixture of components including 51% lactose. The three powders were all exposed to high relative humidities (76% or 100%) over a 1-week period and to a humidity cycle to investigate their caking behaviour and interpret their caking mechanisms. The humidity cycle consisted of 2-day exposure to a high relative humidity (RH) followed by 2-day exposure to low RH of 11% and finally 2-day exposure to the original high RH. At the end of each day, cake strength was measured using a force displacement tester and cake water content was also measured. All three powders sorbed much water when exposed to high relative humidities; however, their cake strengths were very different. Cake strength was influenced by glass transition and the ability of the powders to form sinter bridges. All three powders had similar water content profiles during the humidity cycle with water gain at high RH and loss at low RH. The cake strength profile of the amorphous maltodextrin powder and amorphous SMP were different even though the maltodextrin and lactose glass transition temperatures were reduced below the powder temperature during exposure to high RH. The cake strength of maltodextrin decreased during low RH exposure while it increased for SMP. The cake strength profile of the SMP was similar to the crystalline NaCl. The paper presents an interpretation of the caking mechanisms behind the caking behaviour of each powder.

In this paper, we report the possibility to form glassy molecular alloys (α-lactose)1−x(mannitol)x for x