19 research outputs found
Application of thermal analysis to ibuprofen and associated formulation excipients
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Controlled Microwave Processing Applied to the Pharmaceutical Formulation of Ibuprofen
The first successful development of controlled microwave processing for pharmaceutical
formulations is presented and illustrated with a model drug (ibuprofen) and two excipients (stearic acid
and polyvinylpyrrolidone). The necessary fine temperature control for formulation with microwave
energy has been achieved using a uniquely modified microwave oven with direct temperature
measurement and pulse-width modulation power control. In addition to comparing microwave and
conventional heating, the effect of the presence of liquid (water) in aiding the mixing of the drug and
excipient during formulation was also investigated. Analysis of the prepared formulations using
differential scanning calorimetry and dissolution studies suggest that microwave and conventional
heating produce similar products when applied to mixtures of ibuprofen and stearic acid. However, the
differences were observed for the ibuprofen and polyvinylpyrrolidone formulation in terms of the
dissolution kinetics. In all cases, the presence of water did not appear to influence the formulation to any
appreciable degree. The application of controllable microwave heating is noteworthy as fine temperature
control opens up opportunities for thermally sensitive materials for which microwave methods have not
been feasible prior to this work
Thermal Stability Investigation and the Kinetic Study of Folnak® Degradation Process Under Nonisothermal Conditions
The nonisothermal degradation process of Folnak® drug samples was investigated by simultaneous thermogravimetric and differential thermal analysis in the temperature range from an ambient one up to 810°C. It was established that the degradation proceeds through the five degradation stages (designated as I, II, III, IV, and V), which include: the dehydration (I), the melting process of excipients (II), as well as the decomposition of folic acid (III), corn starch (IV), and saccharose (V), respectively. It was established that the presented excipients show a different behavior from that of the pure materials. During degradation, all excipients increase their thermal stability, and some kind of solid–solid and/or solid–gas interaction occurs. The kinetic parameters and reaction mechanism for the folic acid decomposition were established using different calculation procedures. It was concluded that the folic acid decomposition mechanism cannot be explained by the simple reaction order (ROn) model (n = 1) but with the complex reaction mechanism which includes the higher reaction orders (RO, n > 1), with average value of <n > = 1.91. The isothermal predictions of the third (III) degradation stage of Folnak® sample, at four different temperatures (Tiso = 180°C, 200°C, 220°C, and 260°C), were established. It was concluded that the shapes of the isothermal conversion curves at lower temperatures (180–200°C) were similar, whereas became more complex with further temperature increase due to the pterin and p-amino benzoic acid decomposition behavior, which brings the additional complexity in the overall folic acid decomposition process