Fluorimetric study on a novel FDA-approved combination used for the treatment of overactive bladder syndrome in different matrices

For the first time, two spectrofluorimetric techniques were created for the concurrent determination of mirabegron (MBN) and solifenacin (SOL) in different matrices. This novel combination recently received FDA approval to treat overactive bladder syndrome and was marketed under the brand name MiragoTMS25. SOL has a native fluorescence and can be estimated directly in the presence of MBN without any interference at 290 nm after excitation at 230 nm. In contrast to SOL, MBN is a weak fluorescent substance that requires the use of a fluorogenic reagent (like NBD-Cl) to be measured simultaneously with SOL in their mixtures. So, we reacted MBN with NBD-Cl to yield a yellow-colored fluorophore that could be estimated at 546 nm after excitation at 471 nm without any preliminary separation or interference from SOL. All experimental conditions of the applied methods were tested and enhanced for the best results. The applied fluorimetric methods succeeded in determining both drugs in nanograms, making them applicable in biological fluids like human plasma. The linearity ranges of SOL and MBN were found to be 5-250 ng/mL and 50-600 ng/mL, respectively. The LOD values were 0.96 ng/mL and 5.09 ng/mL for SOL and MBN, in order. Excellent results were attained for both drugs during their analysis in spiked plasma samples employing the applied fluorimetric methods, confirming their suitability for use in real human plasma samples and paving the way for further bioequivalence studies on both drugs.