Thermodynamic Solubility Profile of Temozolomide in Different Commonly Used Pharmaceutical Solvents

The solubility parameters, and solution thermodynamics of temozolomide (TMZ) in 10 frequently used solvents were examined at five different temperatures. The maximum mole fraction solubility of TMZ was ascertained in dimethyl sulfoxide (1.35 × 10(−2)), followed by that in polyethylene glycol-400 (3.32 × 10(−3)) > Transcutol(®) (2.89 × 10(−3)) > ethylene glycol (1.64 × 10(−3)) > propylene glycol (1.47 × 10(−3)) > H(2)O (7.70 × 10(−4)) > ethyl acetate (5.44 × 10(−4)) > ethanol (1.80 × 10(−4)) > isopropyl alcohol (1.32 × 10(−4)) > 1-butanol (1.07 × 10(−4)) at 323.2 K. An analogous pattern was also observed for the other investigated temperatures. The quantitated TMZ solubility values were regressed using Apelblat and Van’t Hoff models and showed overall deviances of 0.96% and 1.33%, respectively. Apparent thermodynamic analysis indicated endothermic, spontaneous, and entropy-driven dissolution of TMZ in all solvents. TMZ solubility data may help to formulate dosage forms, recrystallize, purify, and extract/separate TMZ.