A non-extracting procedure for the determination of meloxicam in plasma samples by HPLC-diode array detection

The bioequivalence of two formulations of 15 mg tablets of meloxicam (CAS 71125-38-7), Meloxicam (LaborMed Pharma) and a commercially available preparation as reference in 24 healthy male and female Caucasian volunteers was assessed based on a validated non-extractive HPLC-DAD method. The sample preparation procedure was based on protein precipitation with a mixture of methanol/acetonitrile, trifluoacetic acid and sodium sulfate solution. Piroxicam (CAS 36322-90-4) was used as internal standard. The stepwise gradient elution profile of the chromatographic method allows injection of a high volume of the sample (500 microL) with the focusing of both analytes in a Chromolith Performance RP-18e column. The mobile phase constituents are methanol and aqueous 20 mmol/L Na2HPO4 buffer solution brought to pH = 6 with H3PO4. A flow-rate of 2 mL/min achieves a complete chromatographic run (including column equilibration) within 12 min. UV detection at 356 nm allowed a quantitation limit around 30 ng/mL. Bioequivalence study was based on an open-label, randomized, two-period, two-sequence, single dose, crossover design with a 2-week wash-out period between consecutive oral administrations. The main pharmacokinetic parameters (C(max), t(max), t 1/2, AUD and AUC(0-infinity)) were considered as evaluation criteria for the bioequivalence of the test drug against the reference.