Fluorimetric Determination of Sulfametoxazole in Pharmaceutical Preparations in Combination with Trimethoprim by Inclusion in β-Cyclodextrin/Urea

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Abstract
The inclusion complex of sulfametoxazole in β-cyclodextrin has been investigated. A 1:1 stoichiometry of the complex has been established and a 226 M−1 formation constant has been calculated by using the changes produced on the fluorescence of the drug when included on the hydrophobic cyclodextrin cavity. An enhancement of the fluorescence emission of sulfametoxazole and protection of the drug against photochemical reactions has been attained upon inclusion. To avoid the problem of the low solubility of β-cyclodextrin in water, solutions of β-cyclodextrin in 8 M urea have been used. A fluorimetric method of determination of sulfametoxazole has been proposed and applied in several pharmaceutical preparations containing trimethoprim, without interference from this compound.