Desenvolvimento de metodologias analíticas para determinação de losartano potássico em cápsulas

Abstract

Losartan potassium is a non-peptide angiotensin II receptor (type AT1) antagonist for the treatment of hypertension. At the present moment, there is not an official method described for the quantification of the drug in pharmaceutical formulations. The aim of this study was to develop analytical methods for losartan potassium quantification in capsules and to establish conditions for accomplishment of the dissolution test for losartan potassium capsules 50 mg. Two spectrophotometric methods were proposed for quantification: direct and first order derivative spectrophotometry, with signals at 205 nm of the zero-order spectrum and 234 nm at the firstderivative spectrum. The employed solvent was distilled water. In addition to these methods, an HPLC method was developed, which the chromatographic parameters were optimized from multivariate approach through the employment of a 25-1 fractional factorial design and the Doehlert matrix. Under optimized conditions, the mobile phase was a potassium phosphate buffer (pH 6.2; 58 mmol L-¹) – acetonitrile (65:35, v/v), pumped at a flow rate of 1.0 mL min-¹ The column was 100 mm × 4.6 mm C8 packed with 5 μm particles and the temperature was fixed in 35 °C. UV detection was performed at 254 nm. To establish the conditions for accomplishment of the dissolution test for losartan potassium in pharmaceutical capsules products tests A, B and C, purchased from three local drugstores were used. Optimal dissolution conditions were obtained from multivariate design through a 24 full factorial design. The use of 72 mmol L-¹ potassium phosphate buffer pH 6.8 as dissolution medium, baskets as apparatus at the stirring speed of 50 rpm and time of 30 min were considered satisfactory. The dissolution sample solutions were quantified by UV spectrophotometric method at 205 nm and by HPLC. The described analytical methods and dissolution procedures were validated presenting selectivity, linearity, precision, accuracy, robustness and desirable limits of detection and limits of quantitation. Finally, all the methods were used for quality control assays of the products tests A, B and C, which demonstrated to be in accordance to regulatory demands.