Browsing by Subject "DSC"

In pharmaceuticals amorphous state can be obtained either intentionally or unintentionally. Intentional production is used, for example, to improve the dissolution of poorly soluble compounds, to stabilize the structure of proteins, or to improve the mechanical properties of excipients (e.g., lactose). Unintentional introduction of amorphous phases can result from general manufacturing procedures of pharmaceuticals, such as coating, granulation, drying, milling, and compression. The presence of amorphous regions, even in small quantities, can exhibit a significant influence on the physical and chemical stability of pharmaceutical products. Molecular mobility in formulation with amorphous content is believed to be the key factor of their stability. Therefore, evaluating of molecular mobility is an important step in pharmaceutical product development. The aim of this study was to estimate molecular motions in amorphous disaccharides using calorimetric approach at temperatures below the glass transition temperature (Tg), where relaxation process is very slow as compared to the time of experiment. When temperature is low enough, the initial relaxation time parameter (τi) can be used as an estimate for relaxation process on the timescale of pharmaceutical product shelf life. The results of the present study revealed similar trend in stability of amorphous forms for the disaccharides (sucrose experiencing the fastest structural relaxation), which can be assumed on the basis of Tg alone, where higher Tg would result in more stable glassy state (Tg of sucrose is the lowest). Storage temperature of Tg - 55oC or lower would suffice for amorphous trehalose, melibiose and cellobiose to achieve at least 2 year's relaxation time, while for sucrose the temperature is Tg - 70oC. Fragility has been used as a helpful mean for classifying amorphous materials. All the compounds can be classified as fragile. Fragility ranking in the present study contains some degree of uncertainty, while 3 different approaches revealed somewhat different results for ranking the disaccharides. The variation in the results can be attributed to the overall sensitivity of DSC. The method described in the present study is quite difficult to apply without supportive information from other techniques. The results, obtained with the method, are very dependent on the slope in plotting ln q vs. 1/Tg, and even small fluctuations in the estimation can lead to different fragility values and consequently to different relaxation times. However, the final results reveal values for relaxation times well below Tg, which are in reasonable agreement with modern theoretical understanding of glassy state dynamics.

The pet medication industry is growing but there are still challenges especially in feline medication. Palatable flavours, efficient taste masking technologies and easily administrable dosage forms are needed to facilitate feline medication. Based on the literature review, there is only little information about cat's preference to individual flavours. The methods for palatability testing should be improved to achieve reliable results. Most common taste masking technologies are flavouring and tablet coating. In experimental section different flavours for taste masking were studied. Five main flavours were selected: phenylalanine, leucine and methionine as possibly good flavours and arginine and denatonium benzoate as bad flavours. In preformulation experiments tableting characteristics, thermal behaviour and crystal structure of flavours were analysed. The aim was also to study their possible incompatibilities with tablet excipients. The main compatilibility study method was X-ray powder diffraction (XRPD), but differential scanning calorimetry (DSC) was also used. Excipient povidone (PVP) was incompatible with nearly all of the main flavours. The use of lactose as an excipient was excluded because of the risk of the Maillard reaction. In tableting studies a tablet mass containing microcrystalline cellulose (MCC), calcium hydrogen phosphate dihydrate, mannitol, hydroxypropyl cellulose (HPC), crospovidone, talc and sodium stearyl fumarate was produced. Minitablets of diameter 3 mm without any flavours were compressed. Also minitablets with flavours phenylalanine and denatonium benzoate were compressed. Minitablets complied with the European Pharmacopoeia tests for uniformity of mass, disintegration and friability. However, characterization and handling of minitablets was found to be challenging due to very small size of the tablets. Minitablets are a promising technology for facilitating feline medication in the future.