Modeling of drug release from delivery systems based on hydroxypropyl methylcellulose (HPMC).

https://onlinelibrary.wiley.com/doi/pdf/10.1021/js9601896

Characteristics and Significance of the Amorphous State in Pharmaceutical Systems

The molecular basis of moisture effects on the physical and chemical stability of drugs in the solid state

Clay and non-clay minerals in the pharmaceutical industry: Part I. Excipients and medical applications

Publisher Summary This chapter focuses on “food polymer science” approach and illustrates various recent examples of the way it has been used to define structure–function relationships in food products and processes and to assess and understand the effects of glass transitions and water plasticization on food quality, safety, and stability. The chapter reviews some theoretical principles from the field of synthetic polymer science that have been shown to be applicable to the studies of the glassy state phenomenon in foods and illustrates those applications by means of a broad overview focusing primarily on the most recent experimental studies by a number of groups that have been especially active in this rapidly growing field of research. The results of such studies have demonstrated the major opportunity offered by the food polymer science approach to expand not only the quantitative knowledge but also, of broader practical value in the context of industrial applications, the qualitative understanding of food products and processes with respect to (1) structure–functional property and water relationships and (2) the influences of nonequilibrium glassy and rubbery states on time-dependent mechanical and rheological properties related to quality and storage stability.

Glass transitions and water-food structure interactions

During formulation development work involving ibuprofen, a solid-state interaction between MgO and ibuprofen was observed. In this study the interaction of MgO and ibuprofen was investigated for 1:1 and 2:1 M mixtures of ibuprofen and MgO, which had been stored at 55 degrees C, using the differential scanning calorimetric (DSC), thermogravic analysis (TGA), and multiple internal reflectance infrared (MIR) techniques. Evidence for the reaction was the disappearance of the melting endotherm at 79 degrees C and appearance of a new endotherm at 161 degrees C after less than 1 day of storage at 55 degrees C and, also, the change in the physical appearance of the mixtures. Comparison of the DSC, TGA, and MIR data for the reacted ibuprofen and MgO mixtures and synthetic Mg(ibuprofen)2 indicated that MgO and ibuprofen react to form the Mg salt of ibuprofen. The interaction of ibuprofen and MgO was also studied at 30 and 40 degrees C, using 1:1 M mixtures. At 30 degrees C no significant interaction was observed for up to 80 days; however, at 40 degrees C a reaction was evident on day 1. NaHCO3, K2CO3 1.5H2O, CaO, and Mg(OH)2 also showed solid-state reactions with ibuprofen. MgCl2 and Al(OH)3 did not show this reaction.

Solid-state interaction of magnesium oxide and ibuprofen to form a salt.

The stability of misoprostol oil is significantly improved in a hydroxypropyl methylcellulose (HPMC) dispersion (1:100). In order to understand the enhanced stability of misoprostol oil in HPMC, the physical state of misoprostol oil in HPMC films was investigated using differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and transmission IR (TIR). Further, to determine the effect of polymer structure and the mobility of both water and misoprostol on misoprostol stability, the rate of misoprostol degradation was investigated in the misoprostol/HPMC dispersion (1:100) at 55 degrees C. The water sorption isotherm of the dispersion at 55 degrees C was determined, at seven different relative humidities, ranging from zero to 81%. The DSC and DMA measurements indicated that misoprostol oil, up to 29% in dry weight, is molecularly dispersed in the glassy HPMC. The TIR studies showed no evidence of complexation between misoprostol and HPMC. Stability studies of the misoprostol/HPMC (1:100) dispersion indicated that the first-order rate constants for misoprostol degradation increased in a concave-up fashion as the water content of the dispersion increased. Below two percent water content, the rate of misoprostol degradation was found to be minimal. Overall, it is suggested that misoprostol is stabilized in the dispersion by being molecularly dispersed in HPMC. Further, the glassy state of HPMC should reduce the mobility of misoprostol and water, leading to a minimal rate of degradation for misoprostol at low moisture levels.

Mechanism of misoprostol stabilization in hydroxypropyl methylcellulose.

Glass–Rubber Transitions of Cellulosic Polymers by Dynamic Mechanical Analysis

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Solid-state interaction of magnesium oxide and ibuprofen to form a salt.

Mechanism of misoprostol stabilization in hydroxypropyl methylcellulose.

Glass–Rubber Transitions of Cellulosic Polymers by Dynamic Mechanical Analysis