A SIMPLE AND SENSITIVE HPLC ASSAY FOR PIROXICAM IN PLASMA AND ITS APPLICATION TO BIOAVAILABILITY STUDY

A rapid, simple and selective method for the determination of piroxicam in human plasma is described. The sample was prepared by direct plasma protein precipitation. Isoxicam was used as the internal standard. For sample analysis, 100-mu-l of the internal standard (isoxicam 500-mu-g/ml) and 50-mu-l of 60% w/v trichloroacetic acid were added to the 500-mu-l of plasma. After brief vortex and centrifugation, the clear supernatant (70-mu-l) was injected onto the HPLC column. Chromatographic separation and quantitation was performed by reversed-phase HPLC using a 5-mu-m CN (Spherisorb) microbore column. The mobile phase consisted of an acetronitrile-water mixture (6 : 94, v/v) containing 10 mM Na2HPO4, adjusted to pH 2. The eluant was monitored at 363 nm. The lower limit of sensitivity for piroxicam is 0.05-mu-g/ml (i.e., 50 ng/ml). The standard curve was linear over the concentration range of 0.05 to 10-mu-g/ml. The intra- and interassay coefficients of variation were less than 8%. Applicability of the method is demonstrated by a bioavailability study in 18 healthy volunteers who received a single oral dose of 30 mg piroxicam.