Aim: To determinate tramadol and O-desmethyltramadol in human plasma and amniotic fluid by LC/MS/MS, and distribution of tramadol and O-desmethyltramadol in maternity and fetus were studied.
Methods: Samples containing tramadol, O-desmethyltramadol and diphenhydramine (internal standard, IS ) were extracted using liquid-liquid extraction, followed by liquid chromatographic separation and on-line MS/MS using atmospheric pressure chemical ionization as an interface detection. The analytes were detected in the selected reaction monitoring mode.
Results: The calibration curves for tramadol and O-desmethytramadol in plasma and amniotic fluid were linear in the range from 8.0 to 800.0 microg x L(-1) (plasma) and 1.0 to 400.0 microg x L(-1) (amniotic fluid). The method was applied to the measurement of tramadol and O-desmethytramadol concentrations in maternal vein, umbilical vein, umbilical artery and amniotic fluid. Following intramuscular pre-operative administration 1.5 mg x kg(-1) doses of tramadol to parturients, plasma concentrations of tramadol were significantly higher than those in amniotic fluid. The concentrations of O-desmethyltramadol in plasma were lower, and were not detected in amniotic fluid.
Conclusion: The method is shown to be accurate, robust and convenient, and suitable for clinical pharmacokinetics studies of tramadol and O-desmethyltramadol.