Solubility study of tolbutamide in monocomponent and dicomponent solutions of water

Abstract

Solubility of tolbutamide was studied in different monocomponent (aqueous solutions of surfactant or β-cyclodextrin) and dicomponent solutions (aqueous solutions of surfactant with β-cyclodextrin). Surfactants used were Tween 20 (Polysorbate 20), Brij 35 (Poloxyl 23 lauryl ether) and sodium lauryl sulphate. In dicomponent solutions, surfactant/ β-cyclodextrin ratios were 1:1, 1:2, 1:3 mol/mol. Results of drug solubility from demineralised water and monocomponent solutions containing different surfactants in various concentrations were almost the same, even though most of the used concentrations were above the critical micelle concentrations of some of the surface active agents. Although tolbutamide/ β-cyclodextrin inclusion compound was formed in the monocomponent solutions of β-cyclodextrin, however, the formation of an inclusion compound was impeded in the Brij 35/ β-cyclodextrin and sodium lauryl sulphate/ β-cyclodextrin dicomponent solutions. Data indicate that surfactants compete with drug molecules to form inclusion compounds with β-cyclodextrin and eventually modify the drug solubility. Results also demonstrate that the resultant competitive binding depends on the chemistry of surface active agents.