Thermal decomposition of D-cycloserine and terizidone in the air and in the inert helium and nitrogen media was studied using differential thermal analysis. It is shown that upon reaching 145 °C and 135 °C respectively, the intense exothermic decomposition begins. In the inert environment the substances retain ability to intensively exothermic decomposition, which is a required condition for the possibility of explosive transformation occurrence. To confirm the possibility of explosive transformation, the flash points of substances were calculated according to the formula, which is a consequence of the problem of thermal explosion during convective heat exchange with the environment. The obtained result is close to the experimental one (temperatures 102 and 104 °C, respectively). The calculations used the kinetic parameters determined by the Kissinger method and corresponding to the values obtained by the Ozawa — Flynn — Wall method. Densities of the substances found using an automatic pycnometer, and the heat of explosive transformation obtained experimentally and with the use of the computer thermodynamic program Real are also considered. It is concluded that both substances are prone to intense exothermic decomposition, and, under certain conditions, the development of a thermal explosion is possible. Recommendations on ensuring industrial safety when working with D-cycloserine and terizidone are sent to FGUP «GNTs «NIOPIK». Particular attention should be paid to temperature control at all the stages of the production process. Based on the results obtained in the study, it should not exceed 110 °C for D-cycloserine, and 120 °C for terizidone considering the error of measuring instruments.

The article studies the mechanism of thermal decomposition of two drugs from the group of isoxazolidines D-cycloserine, and terizidone, potentially exposed to the action of elevated temperatures in production (preparation and drying stages). As a result of series of the analytical experiments on the study of solid products of samples thermal decomposition by IR spectroscopy, including with the participation of a comparative sample (more thermally stable nootropic drug fonturacetam), it was established that the antibiotics D-cycloserine and terizidone containing in their molecular formula a five-membered heterocycle with the [–C–O–N–] group (absorption band in the area of 1461 cm–1) have low thermal stability associated with the ease of breaking N–O bond. It is noted that at the maximum degrees of decay, the specified absorption band weakened until it completely disappeared. The obtained results on thermal decomposition, apparently, can be interpolated to all the substances having specified heterocycle in the structure, which is explosiphoric. Before launching into production, when modeling substances with the specified pharmacological properties, it is required, if possible, to avoid structures with a similar heterocycle with a choice of more heat-resistant analogues that are not inferior in efficiency. Such solutions to reduce fire hazard at the stage of development of technological processes seem to be the most efficient. The study results confirming the propensity of the studied compounds to thermal decomposition at relatively low temperatures contributed to the creation of a safe technological process, storage and transportation conditions at the place of production of FGUP «GNTs «NIOPIK».