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VALIDATED SPECTROPHOTOMETRIC METHODS FOR SIMULTANEOUS DETERMINATION OF BRINZOLAMIDE AND TIMOLOL MALEATE IN THEIR PURE FORM AND OPHTHALMIC PREPARATION

Four sensitive, simple and precise spectrophotometric methods for the simultaneous determination of brinzolamide (BRZ) and timolol maleate (TML) in their pharmaceutical formulation are developed and validated. Method A is the ratio difference spectrophotometric method (RDSM) which can measure the difference in amplitudes between 251 and 265 nm of ratio spectrum for brinzolamide and between 285 and 306 nm of ratio spectrum for timolol. Method B is the mean centering of ratio spectra method (MCR) by measuring the peak amplitude at 252 nm for brinzolamide and 304 nm for timolol. Method C is area under the curve (AUC) in which the area under the curves for brinzolamide and timolol were selected over the ranges of (260265) and (282-288) nm. Method D is the bivariate method (BVM) which depended on the quantitative evaluation of the absorbances at 265 and 285 nm, respectively. Beer’s Lambert’s law for the adopted methods were obeyed over the concentration range of 636 μg/mL for Brinzolamide and 6-42 μg/mL for Timolol. The obtained results were statistically compared with those obtained by the reported methods, showing no significant difference. The suggested methods were validated according to the ICH guidelines and were successfully applied for simultaneous determination of brinzolamide and timolol maleate in bulk drug and in their ophthalmic preparation.