Choline chloride-based DESs with citric acid, tartaric acid, malonic acid and PEG-400 as hydrogen bond donors were prepared. The equilibrium solubility of sparingly water-soluble pyrazinamide was measured in aqueous mixtures of binary and ternary DESs at different DES concentrations in temperature range 293.15–313.15 K. DES of choline chloride/malonic acid/PEG composition showed the strongest solubilizing effect and increased the drug solubility to 46.8 mg∙ml−1 at standard temperature, which is 2.6 times higher than its solubility in water. It was found that increasing the DES content in the mixture and increasing the temperature contribute to improving the drug solubility. Intermolecular interactions in DES/pyrazinamide systems were studied by FTIR spectroscopy. It is shown that Hansen solubility parameters can be used to predict drug compatibility with eutectic solvents. The densities of DES aqueous mixtures are measured in the range of 0.0–1.0 mass fractions of the eutectic solvent at different temperatures and the excess volumes are calculated. It is concluded that with decreasing density of binary DESs, their solubilizing ability for the studied drug increases. In addition, the thermodynamic functions of drug dissolution in the studied DESs are discussed.
