A Validated Reversed-phase HPLC Assay for the Determination of Meloxicam in Human Plasma

A simple and precise reversed-phase high performance liquid chromatography (HPLC) method for the determination of meloxicam in human plasma was developed and validated. Using piroxicam as an internal standard (IS), separation was achieved on Symmetry shield RP-18 column. 0.5 ml plasma samples were prepared by protein precipitation using trifluoroacetic acid and acetonitrile. The mobile phase consisted of 0.025 M dibasic potassium phosphate (pH=6.0, adjusted with phosphoric acid), methanol, and acetonitrile (73:5:22, v:v:v) and was delivered at a flow rate of 1.5 ml/min. Eluents were measured using photodiode array detector set at 355 nm. Under these conditions, no interference in blank plasma or of commonly used drugs was observed. The relationship between the concentration of meloxicam in plasma and peak height ratio of meloxicam to the IS was linear over the range of 0.05-2.0 μg/ml. Intra-day and inter-day coefficient of variations (CV) and biases were ≤ 6.0% and ≤ 8.6%, and ±5.9% and ±5.3%, respectively. Extraction recovery of meloxicam and the IS from plasma was ≥80% and 98%, respectively. The method was applied to assess the stability of meloxicam under various clinical laboratory conditions. In processed samples, meloxicam was stable for at least 24 hours at room temperature (≥ 82%) and 48 hours at -20C (≥ 95%). In unprocessed sample it was stable for at least 24 hours at RT (≥ 82%), 16 weeks at -20ºC (≥ 87%), and after three freeze-thaw cycles (≥ 90%). The method is suitable for clinical and bioavailability investigation involving meloxicam concentration in the therapeutic range.