ABSTRACT The triple fixed‐dose triple combination of bimatoprost, brimonidine, and timolol was proved to treat glaucoma and eye hyperpressure. The separation and simultaneous evaluation of timolol, brimonidine, and bimatoprost was not described till now in any reported work. An efficient method using HPLC and photodiode array detector (PDA) was established herein to evaluate timolol, brimonidine, and bimatoprost. The method we established herein is competent of measuring timolol, brimonidine, and bimatoprost across a linear dynamic range of 5.00–75.00, 0.10–1.50, and 1.50–22.50 µg/mL, respectively, using an ODS C18 column (4.6 mm × 150 mm; particle size 3.5 µm) kept at an ambient temperature and mobile phase consisted of a fixed isocratic ratio of 40:60 (v/v) of acetonitrile to 0.1% (v/v) trimethylamine. The analyses were conducted at an operational wavelength of 240 nm using a PDA detector. Validated successfully and thoroughly the HPLC conditions for analysis employing ICH guidelines. The stress study is carried out to prove stability and indicative nature of assay method of ophthalmic solutions containing bimatoprost, brimonidine, and timolol. The sample solution was stressed by different conditions like hydrolytic (acid/base/neutral), thermal, oxidative, and photolytic. The sample of, when subjected to neutral hydrolytic conditions, the three drugs demonstrated greater stability. Timolol and brimonidine had the highest susceptibility to oxidation, whereas bimatoprost showed a higher susceptibility to hydrolysis with alkali. All degradation products can be efficiently separated from timolol, brimonidine, and bimatoprost using our established evaluation approach. This developed method may be efficiently used in routine analysis of assay of timolol, brimonidine, and bimatoprost drug product samples as well as stability study samples.
Zaheer et al. (Sun,) studied this question.