Pharmaceutical hydrates

Probing Pseudopolymorphic Transitions in Pharmaceutical Solids using Raman Spectroscopy: Hydration and Dehydration of Theophylline

“…As can be seen, the spectral differences between the TPa and TPh forms spread out through almost the entire spectral range. According to a previous study, 65 these are related to the stretching modes of the oscillators C (8) All these spectral regions were evaluated for their suitability to be used in the relative quantification of the two forms, TPa and TPh, using physical mixtures of known TPa/TPh ratio. Two main criteria were considered.…”

“…6 This solid-state transformation can have significant effects on a variety of physical and chemical properties, and eventually modify the pharmaceutical properties, such as solubility, dissolution and bioavailability. 7,8 Thus, detection and understanding of the interactions of water and drugs is of utmost relevance in order to improve and control the quality of the final product.…”

Oiling out or molten hydrate—liquid–liquid phase separation in the system vanillin–water

“…If other solvents are considered, these numbers rise further. This multiplicity of paths available to the molecules in crystallization can lead to problems, as different polymorphs and solvates of a substance differ in their physical properties, such as rate of dissolution (affecting bioavailability), stability, toxicity, and formulation parameters such as powder flow, compactibility, lubricity and hardness 4,5 . Besides using different temperatures and cooling rates, manufacturing processes often involve different solvents; hence, understanding the thermodynamics and kinetics of crystallization for the particular system is of great importance.…”

Pseudopolymorphic transitions of niclosamide monitored by Raman spectroscopy

“…Furthermore, drug substances and drug products are submitted to different temperatures and relative humidities during storage (namely, due to climatic conditions), giving rise to unexpected hydration or dehydration aging phenomena that are known to affect several drug properties, such as solubility, dissolution rate, stability, and bioavailability. 12,44 As described above, the exposure to extreme RH values (0 and 100%) results in total NCa $ NCh interconversion in substantially less than 2 weeks. However, at intermediate RH values, the same processes were found to occur in a much larger time scale.…”

“…10,11 Hydration and dehydration processes of a pharmaceutical solid during formulation development or in a final dosage form may adversely affect the physical, chemical, and/or biological performance of a pharmaceutical product. 12 When polymorphism/pseudopolymorphism is known to occur, spectral methods of analysis can be of great value Ł Correspondence to: Paulo J. A. Ribeiro-Claro, CICECO, Departamento de Química, Universidade de Aveiro, P-3810-193 Aveiro, Portugal.…”