Surface treatment of the hydrophobic drug danazol to improve drug dissolution

The adsorption of the surfactant docusate sodium USP from aqueous solution onto the hydrophobic drug danazol USP has been investigated in relation to wetting and drug dissolution. An adsorption isotherm was constructed after equilibration of the drug in surfactant solutions with initial concentrations in the range 0.1 to 10(4) mu M to determine docusate sodium uptake using the solution depletion technique. Danazol samples were treated with aqueous surfactant solutions at 30 degrees C for 24 h, followed by filtration and drying of the treated drug. The treated and untreated samples were compared using particle dispersion, microelectrophoresis, contact angle and in vitro drug dissolution techniques and the results used to elucidate mechanisms for adsorption and consequent changes in drug dissolution. In all cases, the adsorbed docusate sodium improved the wetting and dissolution of the hydrophobic drug danazol. Reduction in contact angle from 91 degrees for untreated danazol to 62 degrees was achieved at typically low (0.02% w/w) surfactant uptake values, with a corresponding increase in drug dissolution rate. (C) 1998 Elsevier Science B.V. All rights reserved.