A highly sensitive, simple and rapid spectrofluorimetric method was developed for the determination of Amlexanox (AMX) in its bioadhesive buccal tablets. The proposed method is based on measuring the native fluorescence of the methanolic solution of AMX at 400 nm after excitation at 242 nm in 0.2 M borate buffer (pH 10) and 0.5% w/v sodium dodecyl sulfate (SDS) solution. The interaction of AMX with SDS was studied, and the enhanced fluorescence intensity was exploited to develop an assay method for the determination of AMX. The relative fluorescence intensity-concentration plot was rectilinear over the range 5.0-80.0 ng/mL, with a lower detection limit of 0.57 ng/mL and a lower quantification limit of 1.74 ng/mL. The proposed method was successfully applied to the analysis of AMX in its commercial tablets. Moreover, content uniformity testing was conducted by applying official USP guidelines. Statistical evaluation and comparison of the data obtained using the proposed and comparison methods revealed good accuracy and precision for the proposed method.

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A highly sensitive, simple and rapid spectrofluorimetric method was developed for the determination of lacidipine (LCP) in tablets. The proposed method is based on the investigation of the fluorescence spectral behavior of LCP in both sodium dodecyl sulphate (SDS) and the tween-80 micellar system. In aqueous solutions of acetate buffer (pH 4.5), the fluorescence intensities of LCP were greatly enhanced (ca. 2.4 and 4.3 folds) in the presence of either SDS or tween-80, respectively. The fluorescence intensity was measured at 444 nm after excitation at 277 nm using either SDS or tween-80 as a surfactant. The fluorescence-concentration plots were rectilinear over the ranges of 50.0-500.0 ng/ml and 5.0-200.0 ng/ml with lower detection limits of 5.11 and 2.06 ng/ml and lower quantification limits of 17 and 6.87 ng/ml using SDS and tween-80, respectively. The method was successfully applied to the analysis of LCP in commercial tablets and the results were in good agreement with those obtained with the comparison method. Furthermore, content uniformity testing of pharmaceutical tablets was also conducted.

A highly sensitive and simple spectrofluorimetric method was developed for the determination of cyproheptadine hydrochloride (CYP) in its pharmaceutical formulations. The proposed method is based on the investigation of the fluorescence spectral behaviour of CYP in a sodium dodecyl sulphate (SDS) micellar system. In aqueous solution, the fluorescence intensity of CYP was greatly enhanced (150 %) in the presence of SDS. The fluorescence intensity was measured at 410 nm after excitation at 280 nm. The fluorescence-concentration plot was rectilinear over the range 0.2-2.0 μg/mL, with lower detection limit of 0.06 μg/mL. The proposed method was successfully applied to the assay of commercial tablets as well as content uniformity testing. The application of the proposed method was extended to test the in-vitro drug release of CYP tablets, according to USP guidelines. The results were statistically compared with those obtained by official USP method and were found to be in good agreement.

Two simple, accurate and highly sensitive spectrofluorometric methods were developed for the determination of ethamsylate (ETM). Method I is based on measuring the native fluorescence of ethamsylate in water at 354 nm after excitation at 302 nm. The calibration plot was rectilinear over the range of 0.05-1 μg/mL for ETM with limits of detection and quantitation of 7.9 and 26 ng/mL, respectively. Method II involved synchronous and first derivative synchronous fluorometric methods for the simultaneous determination of ethamsylate (ETM) and hydroquinone (HQ) which is considered as an impurity and/or acidic degradation product. The synchronous fluorescence of both the drug and its impurity were measured in methanol at Δ λ of 40 nm. The peak amplitudes ((1)D) were estimated at 293.85 or 334.17 nm for ETM and at 309.05 nm for HQ. Good linearity was obtained for ETM over the ranges 0.1-1.4 μg/mL and 0.1-1.0 μg/mL at 293.85 and 334.17 nm, respectively. For HQ, the calibration plot was rectilinear over the range of 0.01-0.14 μg/mL at 309.05 nm. Limits of detection were 20, 2.01 ng/mL and limits of quantitation were 60, 6.7 ng/mL for ETM and HQ by method II, respectively. Both methods were successfully applied to commercial ampoules and tablets. The results were in good agreement with those obtained by the reference method. Method I was utilized to study the stability of ETM and its degradation kinetics using peroxide. The apparent first-order rate constant, half-life times and activation energy of the degradation process were calculated. Method I was further extended to the in-vitro and in-vivo determination of ETM in spiked and real plasma samples. The mean% recoveries were 99.57 ± 3.85 and 89.39 ± 5.93 for spiked and real human plasma, respectively.