Determination of meloxicam in human plasma by liquid chromatography-tandem mass spectrometry following transdermal administration.

A highly sensitive and selective liquid chromatography-tandem mass spectrometry (LC-MS-MS) method was developed to determine meloxicam of low concentration in human plasma. After a simple sample preparation procedure by one-step protein precipitation with methanol, meloxicam and the internal standard piroxicam were chromatographed on a Zorbax SB C(18) column. The mobile phase consisted of acetonitrile-water-formic acid (80:20:0.2, v/v/v). Detection was performed on a triple quadrupole tandem mass spectrometer by selected reaction monitoring (SRM) mode via electrospray ionization (ESI) source. The method had a lower limit of quantification of 0.10 ng/ml. The calibration curve was demonstrated to be linear over the concentration range of 0.10-50.0 ng/ml. The assay was specific, accurate (percentage deviations from nominal concentrations were within +/-2.5%), precise (intra- and inter-day relative standard deviation (R.S.D.) <7%). The validated method was successfully applied to the determination of meloxicam in human plasma collected up to 180 h after a transdermal administration of 30 mg meloxicam for evaluation of the pharmacokinetics.