A Reliable Method to Quantify Trimethoprim and Sulfamethoxazole in Plasma of Children by HPLC with Application in Pharmacokinetic Studies

Abstract

Aim: To develop a simple and sensitive high-performance liquid chromatography method to determine plasmatic levels of trimethoprim/sulfamethoxazole in paediatric population. Method: Chromatographic separation was carried out using a reverse phase column with detection ultraviolet at a wavelength of 225 nm. The mobile phase consists of phosphate buffer 0.1 M, acetonitrile and methanol, (65:20:15) with a flow of 1.0 ml/min. Results: Calibration curve was linear over the concentration range for trimethoprim of 0.25 to 5 μg/ml and 5 to 100 μg/ml for sulfamethoxazole. Precision were found to be within 15% for both compounds. The detection limits and quantifications for trimethoprim/sulfamethoxazole were 0.2 - 0.25 μg/ml and 3 - 5 μg/ml respectively. Conclusions: The developed method was applied for the quantification of both compounds in plasma samples of two patients resulting concentrations within the therapeutic ranges. The method is convenient for pharmacokinetic studies.