Authors:Márcia Pinto, Elisana de Moura, Fábio de Souza, and Rui Macêdo
Nitroimidazoles are heterocycle imidazoles with a nitrogen group incorporated in its structure. The objective of this study
was to develop a model to characterize possible interactions between active substances and excipients using: Thermogravimetry,
Differential Thermal Analysis, Differential Scanning Calorimetry, and DSC coupled to photovisual system. It was used three
nitroimidazoles (metronidazole, secnidazole, and tinidazole) and two types of microcrystalline cellulose with different particle
size (Microcel and Avicel). The binary mixtures were prepared in proportion (w/w) 1:1 (nitroimidazole:excipient). Thermogravimetric
data demonstrated that the tinidazole was the nitroimidazole with better uniformity. The nitroimidazoles obeyed the zero order
kinetic reaction, evidencing its vaporization processes. Differential thermal analysis data showed nitroimidazoles compatibility
with the different microcrystalline celluloses studied, showing that microcrystalline celluloses stabilized the active substances.
Calorimetric data of secnidazole showed two melting points, characteristic of the polymorphs presented in raw material. The
vaporization constants values of nitroimidazoles studied were secnidazole > metronidazole > tinidazole and for the binary
mixtures these values followed the order tinidazole > metronidazole ≥ secnidazole.
Authors:Elisana Moura, Lidiane Correia, Márcia Pinto, José Procópio, Fábio de Souza, and Rui Macedo
This article had studied the thermal characterization of the raw material and different fluconazole crystals, obtained through
recrystallization with different solvents using thermoanalytical techniques (TG, DTA, DSC-50, DSC Photovisual, DSC-60) and
Pyr-GC/MS. The results confirmed that the fluconazole volatilizes without decomposition until 250 °C. Pyr-GC/MS showed hexachlorobenzene
like impurities in fluconazole raw material.
Authors:Ana Santos, I. Basílio, F. de Souza, A. Medeiros, Márcia Pinto, D. de Santana, and R. Macêdo
Thermal analysis is an essential analytical tool in development of new formulations as well as to study the interaction between
drugs and excipients. This work aims to investigate the possible interactions between metformin and excipients as microcrystalline
cellulose (Microcel MC101®), starch sodium glycolate (Explosol®), sodium croscarmellose (Explosel®), PVP K30, magnesium stearate,
starch and lactose, usually employed in pharmaceutical products. TG, DSC and DTA techniques were used for the thermal characterization
to track if the thermal properties of the drug substance were modified in the mixture. Disregard of the starch and lactose
systems, no changes in thermal behavior of mixtures were found. Thermogravimetric studies (TG) of metformin and its binary
mixtures showed different thermal behavior.
Authors:Antonilêni Medeiros, Ana Santos, F. de Souza, J. Procópio, Márcia Pinto, and R. Macêdo
Stability of drugs
and products has a great practical interest, which is facing to strict regulation.
Thermal studies, besides the determination of the thermal properties of the
investigated product allow the verification of possible interactions between
the drug substances and excipients. The objective of this work was to obtain
solid pre-formulates of paracetamol (PC) by spray drying (SPDR), as well as
to investigate their thermal behavior. Dynamic and isotherm TG, conventional
DSC and DSC-photovisual coupled methods were used to characterize the conventional
and pre-formulated mixtures obtained by SPDR. The results of both DSC investigations
showed slight alterations in melting temperatures, which suggests incompatibilities.
The TG decomposition data of the mixtures evidenced that the dry process via
SPDR leads to stability enhancement of the pre-formulated mixtures.
Authors:Agna Hélia de Oliveira, Elisana Afonso de Moura, Márcia Ferraz Pinto, José Valdilânio Virgulino Procópio, Valmir Gomes de Souza, Fábio Santos de Souza, and Rui Oliveira Macêdo
This work studied the thermal characterization of the pentoxifylline raw material through thermoanalytical techniques (TG, DSC, DSC-photovisual) and analysis of degradation products by Pyr-GC/MS. The picture obtained with DSC-photovisual showed the total vaporization of pentoxifylline at 230.0 °C. The TG dynamical curve presented only one step for the loss of mass evidencing to be a kinetic process of zero order reaction. The pyrograms obtained for pentoxifylline sample in the solid state and solution in the temperatures of 250.0, 300.0, and 400.0 °C, showed only one peak identifying the pentoxifylline.