Abstract

This study aimed to develop and validate a high performance liquid chromatography with ultraviolet method for simultaneous quantification of sulfamethoxazole and trimethoprim in rat plasma after parenteral administration of nanoparticles coated with chitosan, supporting preclinical pharmacokinetic studies for toxoplasmosis treatment. The method used a C18 column at 30°, mobile phase (triethylamine, acetonitrile, water; 1:20:79, pH 5.9), flow rate of 1.0 ml/min, and detection at 268 nm (sulfamethoxazole) and 240 nm (trimethoprim). The validation was assessed by selectivity, linearity, precision, accuracy, and stability. Results showed symmetrical peaks with retention times of approximately 3.0 min (caffeine, internal standard), 4.0 min (trimethoprim), and 7.9 min (sulfamethoxazole), confirming no matrix interference and selectivity of the method. Linearity was achieved for sulfamethoxazole (0.5-50 μg/ml) and trimethoprim (0.1-10 μg/ml), with r2>0.97. Precision and accuracy were validated via relative standard deviation (RSD<15 %) and recovery was within the range of 95 to 103 % for both drugs. Stability was confirmed under controlled storage (CV<15 %), ensuring drug integrity. The validated method was applied to simultaneous determination of sulfamethoxazole and trimethoprim released by nanoparticles coated with chitosan in plasma of rats after parenteral administration. It supports preclinical studies for this innovative toxoplasmosis formulation.