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The stability of active pharmaceutical ingredients (APIs) and the corresponding pharmaceutical formulations are nowadays of great importance in pharmaceutical research and technology. The quality of an API or of finished pharmaceutical products (FPPs) is time dependent under the influence of several parameters, such as light and air exposure, temperature, and humidity. Additionally, the stability profile of an API is influenced by the formulation composition, due to the presence of excipients or by the characteristic of the packaging materials. In this sense, the main objective of this study was to analyze the degradation kinetics of the antihypertensive drug moxonidine as a pure ingredient (MOX) and in two different solid mixtures, one corresponding to a pharmaceutical formulation (MOXTAB) and the other to an enriched pharmaceutical formulation in MOX (MOXMIX). As investigation techniques, FTIR (Fourier transform infrared) spectroscopy and TG/DTG/HF analysis were employed, while the thermoanalytical data were processed according to the ASTM E698 kinetic method and the isoconversional methods of Flynn–Wall–Ozawa (FWO) and Friedman (FR). The kinetic methods revealed that the excipients have a stabilizing effect on MOX (in terms of Ea values), but the decomposition mechanism of the samples is complex, according to the results suggested by the analysis of Ea vs. α values. [ABSTRACT FROM AUTHOR]

Entacapone, a selective and reversible inhibitor of catechol-O-methyltransferase, is used in the treatment of Parkinson’s disease in combination with levodopa/carbidopa to treat the symptoms of end-of-dose “wearing-off” effect. Considering that new formulations are researched constantly, proper knowledge of the active pharmaceutical ingredients is crucial in the preformulation stages. Kinetic analysis was performed using three methods: one integral—Flynn-Wall-Ozawa method, one differential—Friedman method, and modified nonparametric kinetics method (NPK). The thermoanalytical curves were registered at five different heating rates: β = 5, 7, 10, 12, and 15 °C min−1. Analysis was conducted in the dynamic air atmosphere to highlight potential thermooxidative processes. This paper deals with the investigation of solid-state stability and compatibility of binary mixture of entacapone with various pharmaceutical excipients by two instrumental techniques, such as universal attenuated total reflection Fourier transform infrared and thermal analysis (TG/DTG/HF). The excipients used in the mixture were: mannitol, silicon dioxide, talc, sorbitol, magnesium stearate, and povidone. [ABSTRACT FROM AUTHOR]

This paper describes the thermal investigations and kinetic analysis regarding the solid-state degradation of three compounds used as mental disorder therapeutic agents (antidepressants), namely amitriptyline, desipramine and imipramine. The study was carried according to ICTAC 2000 recommendations, by using three isoconversional methods, namely Flynn-Wall-Ozawa, Kissinger-Akahira-Sunose and Friedman. The differential method of Friedman indicated multistep degradation, which was later confirmed by the nonparametric kinetic method (NPK). NPK method showed that all three tricyclic antidepressants are degraded by two processes. In terms of apparent activation energies for decomposition, the NPK method indicated 123.4 kJ mol for imipramine, 112.3 kJ mol for desipramine and 82.9 kJ mol for amitriptyline, and the results are in good agreement with the ones suggested by isoconversional methods. [ABSTRACT FROM AUTHOR]

Even if up to date, betulonic acid (BA) was not investigated for biological activities as much as other triterpenic derivatives like betulinic acid, and there are several papers describing the synthesis, isolation and investigations-both instrumental and biological-of this compound. In this paper, the kinetic behavior associated with thermal decomposition of BA in oxidative conditions is presented. The kinetic study was realized on the main decomposition process which occurs in the 200-300 °C temperature range, according to the ICTAC 2000 protocol, namely employing three isoconversional methods, one differential (Friedman) and two integral (Kissinger-Akahira-Sunose and Flynn-Wall-Ozawa). In order to separate the multistep contributions to the degradation process of BA, the NPK method was employed. This method suggested that the degradation occurs by two parallel processes, with different energetic contributions, with a mean value of 162.1 ± 5.5 kJ mol. [ABSTRACT FROM AUTHOR]

This paper reports on the synthesis and characterization of two Schiff bases bearing 1,2,4-triazolic moieties, namely 4H-4-(2-hydroxy-benzylidene-amino)-5-benzyl-3- mercapto-1,2,4-triazole and 4H-4-(4-nitro-benzylidene-amino)-5-benzyl-3-mercapto-1,2,4- triazole using thin layer chromatography, melting interval, elemental analysis, spectroscopy and thermal stability studies. [ABSTRACT FROM AUTHOR]

Thermal analysis is one of the most widely used methods for studying the solid state of pharmaceutical substances. TG/DTG and DSC curves provide important information regarding the physical properties of the pharmaceutical compounds (stability, compatibility, polymorphism, kinetic analysis, phase transitions etc.). The purpose of a kinetic investigation is to calculate the kinetic parameters and the kinetic model for the studied process. The results are further used to predict the system’s behaviour in various circumstances. A kinetic study regarding the diazepam, nitrazepam and oxazepam thermal decomposition was performed, under non-isothermal and isothermal conditions and in a nitrogen atmosphere, for the temperature steps: 483, 498, 523, 538 and 553 K. The TG/DTG data were processed by three methods: isothermal model-fitting, Friedman’s isothermal-isoconversional and Nomen-Sempere non-parametric kinetics. In the model-fitting methods the kinetic triplets ( f(α), A and E a) that defines a single reaction step resulted in being at variance with the multi-step nature of diazepines decomposition. The model-free approach represented by isothermal and non-isothermal isoconversional methods, gave dependences of the activation energies on the extent of conversion. It is very difficult to obtain an accord with the similar data which resulted under non-isothermal conditions from a previous work. The careful treatment of the kinetic parameters obtained in different thermal conditions was confirmed to be necessary, as well as a different strategy of experimental data processing. [ABSTRACT FROM AUTHOR]

The aim of this work was to assess the impact of an excipient in a pharmaceutical formulation containing candesartan cilexetil over the decomposition of the active pharmaceutical ingredient and to comparatively investigate the kinetics of degradation during thermolysis in an oxidative atmosphere under controlled thermal stress. To achieve this, the samples were chosen as follows: pure candesartan cilexetil and a commercial tablet of 32 mg strength. As a first investigational tool, Universal attenuated total reflection Fourier transform infrared (UATR-FTIR) spectroscopy was chosen in order to confirm the purity and identity of the samples, as well as to check if any interactions took place in the tablet between candesartan cilexetil and excipients under ambient conditions. Later on, samples were investigated by thermal analysis, and the elucidation of the decomposition mechanism was achieved solely after performing an in-depth kinetic study, namely the use of the modified non-parametric kinetics (NPK) method, since other kinetic methods (American Society for Testing and Materials—ASTM E698, Friedman and Flynn–Wall–Ozawa) led to inadvertencies. The NPK method suggested that candesartan cilexetil and the tablet were degraded by the contribution of two steps, the main being represented by chemical degradation and the secondary being a physical transformation. The excipients chosen in the formulation seemed to have a stabilizing effect on the decomposition of the candesartan cilexetil that was incorporated into the tablet, relative to pure active pharmaceutical ingredient (API), since the apparent activation energy for the decomposition of the tablet was 192.5 kJ/mol, in comparison to 154.5 kJ/mol for the pure API. [ABSTRACT FROM AUTHOR]

In this paper, the thermal stability of pure l -thyroxine (THY) and l -thyroxine sodium salt hydrate (THYSS) vs. two pharmaceutical solid formulations commercialized on both Romanian and European market (with a content of 100 μg, respectively 200 μg THYSS per tablet) were investigated. In order to determine whether the presence of excipients affects the thermal stability of the active pharmaceutical ingredient (API), the preliminary study of thermal stability in air atmosphere was completed with an in-depth solid-state kinetic study. By kinetic analysis, the non-isothermal degradation of the selected active pharmaceutical ingredients vs . the solid formulation with strength of 200 μg THYSS per tablet was investigated. Isoconversional methods (Kissinger–Akahira–Sunose, Flynn-Wall-Ozawa and Friedman) were employed for the estimation of activation energies values, at five different heating rates, β = 5, 7, 10, 12 and 15 °C min −1 . Also, a fourth method was applied in the processing of data, namely NPK, allowing an objective separation in the physical and chemical processes that contribute to the thermal degradation of the selected compounds. A discussion of thermal stability from the kinetic point of view is also presented. [ABSTRACT FROM AUTHOR]