Tracking of the behaviour of lidocaine base containing hydroxypropylcellulose free films with thermoanalytical method

Abstract

The excipients proved to exert strong effects on the physicochemical properties of the tested systems, and it is very important to study them intensively in preformulation studies in pharmaceutical technology. In our earlier paper, we already described the structure of Klucel®-containing films with various physicochemical examinations (tensile strength, surface properties and positron annihilation lifetime spectroscopy). The aim of our present investigations was to study the thermal behaviour of the film-forming polymers with two different chain lengths, of the taste-enhancing and plasticizing excipients and also of the films prepared from them. The thermal behaviour of Klucel® LF and Klucel® MF film-forming polymers was found to differ only in the range of 340–400 °C, which is due to the different chain lengths of the polymer molecules. Among the active ingredients and excipients used, glycerol had the smallest while xylitol showed the greatest thermal stability. The shape of the TG curves shows that the decomposition process changes with the increase in the concentration of the excipients. The TG curves open up more, which is probably due to the fact that the molecules built-in among the polymer chains loosen the structure, which in turn is decomposed more easily. The TG–MS examinations revealed that during decomposition, carbon dioxide was formed in the highest concentration and that acetic acid, isopropyl alcohol and acetone also developed. The shape of the TG curves shows that in the case of the 5 and 10 % systems, the presence of lidocaine did not result in a significant difference in thermal stability.