Abstract: Hydrotropy is a solubilization process whereby addition of large amounts of a second solute results in an increase in the aqueous solubility of another solute. Traditionally hydrotropes occupied a niche somewhere between salts, counterions, surfactants, and cosolvents. There is a growing recognition that hydrotrope behavior is a sequence along the continuum of surfactant behavior and that a great deal of hydrotrope behavior can be understood by treating them as surfactants with very high critical micelle concentrations. Hydrotropic solubilization method is used in enhancement of solubility of various poorly water-soluble compounds.
Introduction
Solubility is defined in quantitative terms as the concentration of the solute in a saturated solution at a certain temperature and in qualitative terms, it may be defined as the spontaneous interaction of two or more substances to form a homogeneous molecular dispersion. A saturated solution is one in which the solute is in equilibrium with the solvent. The solubility of a drug may be expressed as parts, percentage, molarity, molality, volume fraction, and mole fraction.
Drug solubility is the maximum concentration of the drug solute dissolved in the solvent under specific condition of temperature, pH and pressure. The drug solubility in saturated solution in a static property where as the drug dissolution rate is a dynamic property that relates more closely to the bioavailability rate.
Solubilization may be defined as the spontaneous passage of poorly water-soluble solute molecules into an aqueous solution of surfactant. As different molecules interact both repulsive and attractive, forces are operative. The attractive forces are necessary to prevent interpretation of molecules.
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