Simultaneous quantification of trimethoprim metabolites in pediatric plasma

The dual agent antibiotic, trimethoprim/sulfamethoxazole (TMP-SMX), has been prescribed to treat or prevent infections for over 50 years. However, there are no published validated analytical methods for the measurement of TMP metabolites in humans. We developed methodology enabling reliable quantification of TMP and 5 metabolites in human plasma. Chromatographic separation was achieved in less than 8 min using a biphenyl column. Analytes were detected in positive electrospray mode using a tandem Waters Xevo-TQ-XS mass spectrometer. Precision and accuracy values for all analytes were within 15% of nominal values during assay validation.