Solution thermodynamics and solubilization behavior of diclofenac sodium in binary mixture of Transcutol-HP and water

Solution thermodynamics and solubilization behavior of diclofenac sodium (DS) in binary mixture of Transcutol-HP and water is not reported in the literature so far. Therefore, the aim of the present study was to investigate the solution thermodynamics and solubilization behavior of DS in mono-solvents and various Transcutol-water mixtures at 298.15-333.15 K. The mole fraction solubility of DS was determined by shake flask method and thermodynamic parameters (enthalpies and entropies) were calculated with the help of the modified Apelblat model. The experimental solubility data of DS in all sample matrices was found to be correlated well with the modified Apelblat model with correlation coefficients of 0.9950-0.9990. Absolute relative deviation was found to be less than 3% in most of the Transcutol-water mixtures at each temperature studied. The mole fraction solubility of DS was observed to be highest in pure Transcutol (0.139 at 298.15 K) as compared to pure water and other Transcutol-water mixtures. The enthalpies and entropies for DS dissolution were observed as positive values for all cosolvent mixtures which indicated that the dissolution of DS is endothermic and an entropy-driven process. Based on solubility data, DS was considered as sparingly soluble in pure water and freely soluble in Transcutol. These results indicated that Transcutol could be used as an alternate of ethanol, propylene glycol and polyethylene glycol to enhance aqueous solubility of DS. These preliminary studies could be useful in formulation development of DS especially in terms of liquid dosage forms and injectable formulations.