Pioglitazone (PGZ) or 5-[[4-[2-(5-ethylpyridin-2-yl)-ethoxy]phenyl]methyl]-1,3-thiazolidine-2,4-dione with CAS registry number of 111025-46-8 is a low water-soluble oral hypoglycemic agent which is used as its hydrochloride salt. The solubility of the hydrochloride salt (PGZ-HCl, for its chemical structure, see Fig. 1) is still low and may cause problems in many practical applications.1) Different methods for increasing the aqueous solubility of drugs are; cosolvency, addition of surface active agents, salt formation, complexation, hydrotropism, crystal engineering, preparation of soluble prodrug and more recently addition of ionic liquids.
2-8)Solubilization of poorly soluble drugs is essential for preparation of many commercially available oral solutions, parenteral, soft gelatin and topical pharmaceutical formulations.9) Ethanol is one of the most important and common cosolvents in the pharmaceutical industry and is used in many commercially available oral, parenteral and soft gelatin formulations.9) Propylene glycol (PG) is a stable and low toxic cosolvent which is used in many commercially available oral and parenteral formulations.9,10) Polyethylene glycols (PEGs) are neutral polyethers which are freely soluble in water due to strong hydrogen-bonding with water molecules. Their low toxicity and high aqueous solubility make PEGs as a suitable solvent for various applications in the pharmaceutical, chemical, cosmetic and food industries.11) N-Methyl-2-pyrrolidone (NMP) is very strong solubilizing agent 9) and is an important solvent in extraction, purification and crystallization of drugs. 12,13) Experimental solubility data of many pharmaceutical compounds in both water 14) and waterϩcosolvent mixtures 15) are available in comprehensive published data compilations. It is impossible to experimentally determine the solubility of every drug or potential drug candidate in different water-cosolvent mixtures, and considerable effort has been devoted to the development of mathematical models for estimation of drug solubility in water-cosolvent mixtures. These models were reviewed and their advantages and limitations were discussed. 16) One of these models is the Jouyban-Acree model which was used in predicting the solubility of many pharmaceutical and chemical compounds in binary and ternary solvent mixtures at different temperatures. In addition to the solubility prediction, the model has been used to calculate several physicochemical properties in mixed solvent systems.
16)Available solubility data of PGZ and PGZ-HCl was summarized and the solubility of PGZ-HCl in aqueous mixtures of ethanol, PG and NMP at 25°C was reported in previous publications. 17,18) In this work, the solubility of PGZ-HCl in the binary mixtures of PEG 400 with water, ethanol, PG and NMP at 25°C is reported which extends the solubility database of pharmaceutically interested systems.15) The fitness of the data to the Jouyban-Acree model is also investigated.
ExperimentalMaterials PGZ-HCl (with purity of 0.998 in mass fraction) was purchase...