The goal of this study was to develop and validate a liquid chromatography (LC) method for the rapid determination of dipyrone (metamizole sodium) in solid and liquid formulations. Samples were extracted with water and filtered prior to LC analysis. The analytical procedure involved reversed phase LC with a Zorbax SB C-18 column (5 mu m particle size, 4.6 mm x 250 mm i.d.), isoctratic methanol/water (80/20, v/v) mobile phase with UV detection at 254 mn. The flow rate was 1 mL min(-1), injection volume was 100 mu L and retention time of dipyrone was 3.3 min. The method was validated with respect to linearity, precision and accuracy. Calibration curves were linear in the range 0.5-100 mu g mL(-1) for analyte and the recoveries at three levels (10, 15 and 25 mu g mL(-1)) ranged from 93 to 100%. All results for dipyrone were confirmed by liquid chromatography-mass spectrometry (LC-MS) and H-1 nuclear magnetic resonance (NMR) spectroscopy. Due to its simplicity and accuracy, the assay method is suitable for routine analysis of both solid and liquid formulations and seven retail samples were analyzed using the validated method. (c) 2004 Elsevier B.V. All rights reserved.