The objective of present investigation was to measure the solubility and dissolution thermodynamics of N-(4-chlorophenyl)-2-(pyridin-4-ylcarbonyl)hydrazinecarbothioamide [isoniazid (INH) analog] in various propylene glycol (PG) + water co-solvent mixtures from (298.15 to 338.15)K. The experimental solubilities of INH analog were correlated with Apelblat and Yalkowsky models. The root mean square deviations were found to be (1.13-3.98)% and (1.45-5.73)% for Apelblat equation and Yalkowsky model, respectively. Good correlation was observed between experimental and calculated solubilities of INH analog with correlation coefficients in the range of 0.995-0.999. The mole fraction solubility of INH analog was found to be highest and lowest in pure PG (7.38 x 10(-3) at 298.15 K) and pure water (5.17 x 10(-7) at 298.15 K), respectively. The results of dissolution thermodynamics indicated endothermic and non-spontaneous dissolution of INH analog. (C) 2014 Elsevier B.V. All rights reserved.