A RAPID AND SENSITIVE BIOANALYTICAL HPLC METHOD FOR DETERMINING DICLOFENAC SODIUM IN HUMAN PLASMA FOR BIOEQUIVALENCE STUDIES

A simple, rapid, and sensitive HPLC method for determination of diclofenac sodium (DS) in human plasma was developed and properly validated according to US-FDA. One-step extraction of DS was carried out by protein precipitation using acetonitrile. Butyl paraben was used as an internal standard (IS). Chromatographic separation was achieved using C18 reversed-phase column. The mobile phase was acetonitrile: water (pH 4) using isocratic elution at a flow rate of 1.0mL/min. The IS and DS were detected at 282 nm and eluted at 3.3 and 5.6 min, respectively. The lower limit of detection (LLOD), lower and upper limits of quantification (LLOQ and ULOQ) were 0.01, 0.02, and 2.00 mu g/mL, respectively. All the aspects of stability studies (stock solution, freeze-thaw, benchtop, long-term DS stability in plasma) were satisfactory and safe guard the validity and robust of the developed method. The drug in plasma and stock solution in methanol were stable for 5 weeks and 3 months at -20 degrees C, respectively. This method was successfully applied for determination of DS plasma concentrations during a pharmacokinetic study in a healthy human male volunteer after an oral administration of Voltaren 100 mg/tablet manufactured in two different sites (Novartis-Egypt and Switzerland) in a cross-over design.