As per the author’s concept, all substances whether solid, liquid or gas have solubilizing power. The effect of additive depends very much on the influence it has on the structure of water or its ability to compete with the solvent molecule. Melted PEG 4000, PEG 8000 (temperature less than 100°C) and melted urea (M.P.: 132-135°C) dissolves diclofenac sodium (M.P.: 283°C), this shows that PEGs and urea act as solvent for diclofenac sodium. Melted ibuprofen (M.P.: 78°C) dissolves diclofenac sodium (M.P.: 283°C), salicylic acid (M.P.: 159 °C) and niacinamide (M.P.: 132°C) which shows that melted ibuprofen acts as solvent for diclofenac sodium, salicylic acid and niacinamide. The solubility studies on a poorly water-soluble drug, salicylic acid when carried in the solution containing blends of hydrotropic agents (urea and sodium citrate), cosolvent (glycerin, propylene glycol, polyethylene glycol 300 and 400) and water soluble solids (polyethylene 4000 and 6000) individually as well as in ten randomly prepared blends keeping total concentration constant. The present study investigates use of mixed solvency approach in increasing transdermal permeation of Indomethacin.
