Equilibrium solubility of niclosamide in various mediums
Objective To determine the equilibrium solubility of niclosamide in different aqueous mediums,surfactants and organic solvents,thus providing further basis for the content determination,pharmacodynamics study and the design of new dosage forms of the drug.Methods High performance liquid chromatography was used to detect the equilibrium solubility of niclosamide in different aqueous mediums such as saline,5％ glucose solution,pH7.4 phosphate buffer and deionized water at 25 ℃ and 37 ℃.The effect of different surfactants including polysorbate 80(tween-80),sodium dodecyl sulfate(SDS) and sorbitane monooleate (span-80) on the equilibrium solubility of niclosamide were studied at the same time,and the equilibrium solubilities of niclosamide in some common organic solvents,e.g.petroleun ether,tetrahydrofuran were determined.Results Niclosamide was poorly soluble in aqueous mediums.The equilibrium solubilities of niclosamide in saline,5％ glucose solution,pH7.4 phosphate buffer and deionized water were (0.249 7±0.005 3),(0.232 0±0.001 2),(0.552 2±0.005 0),(0.233 9±0.000 6) μg/ml at 25 ℃ and (0.313 2±0.014 5),(0.253 3± 0.005 9),(1.254 0±0.008 6),(0.270 5±0.001 9) μg/ml at 37 ℃,respectively.The solubilizing power of different surfactants were tween-80＞SDS＞span-80.The equilibrium solubility of niclosamide in organic solvents was greater than that in aqueous mediums.Among them,the equilibrium solubility was the highest in tetrahydrofuran and the lowest in petroleum ether,which was(743 7.03±94.40) μg/ml and (50.67±0.66) μg/ml,respectively.Conclusion Niclosamide is a hydrophobic drug.The non-ionic surfactant polysorbate 80 can significantly increase the solubility of the drug.The equilibrium solubility is higher in some organic solvents such as tetrahydrofuran and acetone.
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