ABSTRACT
Objective: For the extraction and quantitation of plasma fluoxetin (FLX), simvastatin (ST) and simvastatin acid (STA), a rapid, robust and sensitive method using solid-phase extraction (SPE) cartridges and high pressure liquid chromatography (HPLC) with ultraviolet (UV) detection was developed.
Material and methods: Waters HLB cartridges were used for the sample clean-up and purification. Separation of analytes and internal standard (IS) mewastatin was achieved using Phenomenex C18 column (150 x 2 mm, 3 μm). Mobile phase consisted acetonitrile and phosphate buffer (65:35, v/v) in isocratic mode with a flow rate of 0.3 ml/min.
Results: The relative retention times for FLX, ST, STA and IS were 1.5, 8.5, 3.7 and 5.0 min respectively. The calibration curves were plotted by using peak area ratios of analytes to IS. The plots were linear from 10-1500 ng/ml for FLX and 10-1000 ng/ml for ST and STA. Intra and inter precision values for FLX ranged from 4.69 to 12.61, for ST 3.36-13.38 and for STA it ranged from 3.73 to 12.93% respectively. The 10 ng/ml was the lowest limit of quantitation (LLOQ) for FLX, ST, and STA.
Conclusion: The specificity and sensitivity of this method make it appropriate to estimate plasma level of FLX, ST, and STA in preclinical studies in a single run.

Keywords: RP-LC, Solid phase extraction, simvastatin, fluoxetin, simvastatin acid.