Uniformity and physical states of troglitazone in solid dispersions determined by electron probe microanalysis and microthermal analysis

Methods to characterize the structure of food powders – a review

Food powders can exist in amorphous, crystalline or mixed structure depending on the order of molecular arrangement in the powder particle matrices. In food production, the structure of powders has a greatly effect on their stability, functionality, and applicability. The undesirable structure of powders can be accidentally formed during production. Therefore, characterization of powder structure as well as quantification of amorphous–crystalline proportions presenting in the powders are essential to control the quality of products during storage and further processing. For these purposes, many analytical techniques with large differences in the degree of selectivity and sensitivity have been developed. In this review, differences in the structure of food powders are described with a focus being placed on applications of amorphous powders. Essentially, applicability of common analytical techniques including X-ray, microscopic, vapor adsorption, thermal, and spectroscopic approaches for quantitative and qualitative structural characterization of food powders is also discussed.

Methods of amorphization and investigation of the amorphous state

The amorphous form of pharmaceutical materials represents the most energetic solid state of a material. It provides advantages in terms of dissolution rate and bioavailability. This review presents the methods of solid- -state amorphization described in literature (supercooling of liquids, milling, lyophilization, spray drying, dehydration of crystalline hydrates), with the emphasis on milling. Furthermore, we describe how amorphous state of pharmaceuticals differ depending on the method of preparation and how these differences can be screened by a variety of spectroscopic (X-ray powder diffraction, solid state nuclear magnetic resonance, atomic pairwise distribution, infrared spectroscopy, terahertz spectroscopy) and calorimetry methods.

Melt extrusion with poorly soluble drugs

Melt extrusion (ME) over recent years has found widespread application as a viable drug delivery option in the drug development process. ME applications include taste masking, solid-state stability enhancement, sustained drug release and solubility enhancement. While ME can result in amorphous or crystalline solid dispersions depending upon several factors, solubility enhancement applications are centered around generating amorphous dispersions, primarily because of the free energy benefits they offer. In line with the purview of the current issue, this review assesses the utility of ME as a means of enhancing solubility of poorly soluble drugs/chemicals. The review describes major processing aspects of ME technology, definition and understanding of the amorphous state, manufacturability, analytical characterization and biopharmaceutical performance testing to better understand the strength and weakness of this formulation strategy for poorly soluble drugs. In addition, this paper highlights the potential advantages of employing a fusion of techniques, including pharmaceutical co-crystals and spray drying/solvent evaporation, facilitating the design of formulations of API exhibiting specific physico-chemical characteristics. Finally, the review presents some successful case studies of commercialized ME based products.

Effect of physical properties of troglitazone crystal on the molecular interaction with PVP during heating

This study examined the effect of physical properties of troglitazone drug substance on the molecular interaction with polyvinylpyrrolidone K30 (PVP) during preparation by a closed melting method. Milling was conducted using impact and jet mills to change the physical properties of troglitazone, such as particle size, specific surface area, surface free energy and acidic-basic parameters. Solid dispersions (SDs) prepared from milled troglitazone, irrespective of milling method, showed almost 100% dissolution when not less than 7.5% of water was added during heating. SDs prepared from unmilled troglitazone showed almost 100% dissolution when not less than 12.8% of water was added during heating. Physical mixture (PM) containing unmilled troglitazone must be heated above at least 50 degrees C higher than the glass transition temperature (T(g)) of PVP to obtain an SD showing 100% dissolution, while PMs containing milled troglitazone could be heated above only 20 degrees C higher than the T(g) of PVP to obtain an SD showing 100% dissolution. The melting points of troglitazone in PMs containing milled troglitazone, irrespective of milling method, were lower than those in PMs containing unmilled troglitazone. These results indicated that specific interaction could occur more easily during heating between milled troglitazone and PVP during preparation by a closed melting method. In addition, Fourier transform infrared study indicated that hydrogen bonding could occur between the N-H of troglitazone and the C=O of PVP.

Analytical techniques for quantification of amorphous/crystalline phases in pharmaceutical solids

The existence of different solid-state forms such as polymorphs, solvates, hydrates, and amorphous form in pharmaceutical drug substances and excipients, along with their downstream consequences in drug products and biological systems, is well documented. Out of these solid states, amorphous systems have attracted considerable attention of formulation scientists for their specific advantages, and their presence, either by accident or design is known to incorporate distinct properties in the drug product. Identification of different solid-state forms is crucial to anticipate changes in the performance of the material upon storage and/or handling. Quantitative analysis of physical state is imperative from the viewpoint of both the manufacturing and the regulatory control aimed at assuring safety and efficacy of drug products. Numerous analytical techniques have been reported for the quantification of amorphous/crystalline phase, and implicit in all quantitative options are issues of accuracy, precision, and suitability. These quantitative techniques mainly vary in the properties evaluated, thus yielding divergent values of crystallinity for a given sample. The present review provides a compilation of the theoretical and practical aspects of existing techniques, thereby facilitating the selection of an appropriate technique to accomplish various objectives of quantification of amorphous systems.

Effects of water content in physical mixture and heating temperature on crystallinity of troglitazone-PVP K30 solid dispersions prepared by closed melting method

Troglitazone, which possesses two asymmetric carbons, is obtained as a mixture of four isomers present in equal amounts. Troglitazone (Lot T003) has two melting points, about 120 and 175 degrees C. To increase the bioavailability of insoluble troglitazone, troglitazone-polyvinylpyrrolidone K30 (PVP) solid dispersions (SDs) were prepared with water by a unique closed melting method. In this study, the effects of the water content in the physical mixture (PM) and the heating temperature on the apparent crystallinity of troglitazone in SDs prepared by this method were investigated. When the water content in the PM was controlled at 3%, although the apparent crystallinity of troglitazone in the SD prepared by heating at 105 degrees C did not decrease (99%), that of the SDs prepared by heating at 130 and 150 degrees C were reduced to 54 and 11%, respectively. This result indicated that the meltage of troglitazone varies depending on the heating temperature. The apparent crystallinity of troglitazone in the SDs decreased with increase in water content in the PM. In particular, SDs prepared by heating at 130 and 150 degrees C showed 0% apparent crystallinity when the water content in the PM were more than 13 and 8%, respectively. When the heating temperature used was higher than the glass transition temperature of PVP plasticized with water, troglitazone crystals were dissolved in the rubbery PVP. Therefore, even if the heating temperature is lower than the melting point of troglitazone during preparation, controlling the water content in the PM at a high level can produce a troglitazone SD with 0% apparent crystallinity.