Fleming Martínez

Tetracycline is a first-line antibiotic used to treat various infections. Given its widespread use in human and veterinary medicine, it is a potentially hazardous emerging contaminant. This study aimed to perform a thermodynamic and preferential solvation analysis of tetracycline in 1,4-dioxane and water cosolvent mixtures. Equilibrium solubility was determined via UV/vis spectrophotometry using the shaking-flask method at temperatures ranging from T/K = 278.15 to T/K = 313.15. Apparent thermodynamic functions were calculated using van’t Hoff and Gibbs equations. Preferential solvation was evaluated using inverse Kirkwood-Buff integrals (IKBI). The results show that solubility increases with temperature and 1,4-dioxane concentration increases. The process is endothermic throughout the system; however, the enthalpy-entropy compensation analysis demonstrates an entropy-driven mechanism for drug transfer from more polar to less polar solvent systems. IKBI analysis confirmed preferential solvation by 1,4-dioxane in all cosolvent mixtures, peaking at a mole fraction of 0.55. 1,4-Dioxane increases solubility by mitigating the large solvent-excluded volume effect characteristic of pure water. This relieves the entropic penalty associated with cavity creation for the bulky drug molecule, while simultaneously promoting favorable specific interactions where tetracycline acts as a Lewis acid toward 1,4-dioxane oxygen atoms.

The main objective of this research was to determine and correlate the equilibrium solubility of sodium sulfamethazine (NaSMT) in several {ethanol (1) + water (2)} mixtures reported in mass/volume and mass/mass percentages at different temperatures, as well as the density of saturated solutions. NaSMT solubility decreases with decreasing temperature, and also decreases non-linearly with the addition of ethanol to water at every temperature. Logarithmic solubility was adequately correlated with a bivariate model involving temperature and mixture composition. Solubility values were also well correlated with some Jouyban–Acree-based models. Moreover, an adapted version of the Jouyban–Acree model was used to represent the density of the saturated systems at different temperatures. Furthermore, the apparent specific volumes of NaSMT at saturation were also calculated from densities of saturated solutions and cosolvent mixtures free of drug at every mixture composition and temperature. These findings provide valuable insights into the solubility and volumetric behavior of NaSMT that could be useful for improving pharmaceutical formulation processes.

Solubility studies are essential for developing more efficient dosing processes and systems. The solubility of INH in a mixture of PEG 300 (1) + water (2) was evaluated at various temperatures using UV/Vis spectrophotometry and the shaking flask method. Solubility increased by 150% at 288.15 K and 298% at 318.15 K, reflecting the temperature dependence of solubility when transitioning from pure water to pure PEG 300. Generally, the solubility of INH is an endothermic process favoured by entropy. Its affinity increases with PEG 300 proportion in the mixtures, transitioning from an enthalpic to an entropic mechanism as it approaches the pure solvent. Ultimately, it is concluded that PEG 300 acts as an excellent, eco-friendly cosolvent that could help to optimise more sustainable pharmaceutical systems.

Objective: Hepatitis C virus (HCV) infection remains a major global health challenge, contributing to chronic liver disease, cirrhosis, and hepatocellular carcinoma. Although direct-acting antivirals (DAAs) have markedly improved treatment outcomes, their high cost and potential adverse effects limit accessibility, particularly in low-resource settings. Consequently, there is increasing interest in exploring medicinal plants ...