Lovastatin (structure shown in Fig. 1), a highly effective cholesterol-lowering agent, belongs to a class of the most powerful lipid lowering agents generally called the statins and is a competitive inhibitor of the enzyme 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase.1) Furthermore, it has been reported that lovastatin has a good effect in reducing lethality in coronary heart disease.2) After oral administration of lovastatin, the plasma levels of the drug has been reported to be very low, which is mainly attributed to the documented extensive hepatic first-pass effect of the drug.
3,4)Although a series of sensitive and accurate methods have been described for determination of lovastatin in biological fluids, but all these methods require the use of sophisticated and relatively non-popular instrumentations such as gas chromatography/mass spectrometry [5][6][7] or, more recently, highperformance liquid chromatography/mass spectrometry, 8,9) the availability of a simple, popular and cost-effective method for this purpose remains a limiting factor against pharmacokinetic studies on this drug. The purpose of this investigation was to develop a rapid, popular, and sensitive analytical method, based on HPLC with UV detection of lovastatin in human plasma in order to, primarily, be used throughout a bioequivalence study. Preparation of Calibration Standards and Quality Control Samples In order to prepare stock standard solution of lovastatin, 100 mg of lovastatin was dissolved in 100 ml methanol. The stock solution was then further diluted with methanol to obtain the different working solutions ranging 40, 100, 200, 400, 1000, 2000, 4000 ng/ml, from which the spiked plasma samples were prepared by appropriate dilution. Quality control (QC) samples were prepared at low (10.0 ng/ml), medium (25.0 ng/ml) and high (50.0 ng/ml) concentrations in the same way as the plasma samples for calibration.
MATERIALS AND METHODS
ChemicalsSamples Preparation A liquid-liquid extraction procedure was used in this study for isolation of lovastatin from the plasma samples. For this purpose, 20 ml of atorvastatin (internal standard; IS) methanolic solution with concentration of 100 mg/ml was added to 2 ml plasma and after vortexmixing for 30 s, 4 ml of diethyl ether was added while the mixture was vortex-mixed for another 1 min. The organic and aqueous layers were then separated by centrifugation at 5000ϫg for 10 min, the organic supernatant was transferred to another tube and evaporated at 40°C to dryness. Finally, the residue was reconstituted in 200 ml mobile phase and following a brief orbital shaking, 50 ml was injected onto the HPLC system. Chromatographic Condition The analytical column was Symmetry C 18 (Waters, U.S.A.) (particle size 5 mm; 250ϫ4.6 mm) with the corresponding guard column An available, simple, sensitive, and rapid method has been developed for determination of the 3-hydroxy-3-methylglutaryl (HMG)-CoA reductase inhibitor, lovastatin in human plasma. The analytical procedure involves a one-step liquid-liquid extr...