Determination of pravastatin by high performance liquid chromatography.

BACKGROUND: Pravastatin is a hydrophilic liver-specific inhibitor of the enzyme 3-hydroxy-3-methylglutaryl coenzyme A reductase. It effectively lowers plasma cholesterol and low-density lipoprotein concentrations in humans. Pharmacokinetic studies of pravastatin have been mostly performed by means of radioactively labelled drug or by measuring plasma concentrations with gas chromatography and mass spectrometry. AIMS OF THE STUDY: Aim of our study was to develop a simple, but reliable method which allows the determination of pravastatin plasma concentrations under clinical routine conditions. SUBJECTS,
MATERIALS AND METHODS: Samples were prepared by solid-phase extraction on cyclohexyl bond elut cartridges. Chromatography was carried out on an octyl matrix. Triamcinolone acetonide was used as internal standard. The method was linear within the range of 5 to 200 microg/l pravastatin. The coefficient of variation depended on the pravastatin concentration, but was less than 10% throughout. The pharmacokinetics of pravastatin were determined in healthy individuals. Five healthy subjects received single oral doses of pravastatin (60 mg) and one of these subjects additionally received a dose of 80 mg at three different study days. In all subjects blood was sampled 0, 30, 60, 90, 120, 150, 180, 240 and 300 min after drug intake.
RESULTS: Peak plasma concentrations of pravastatin were found between 60 min and 120 min after oral administration of 60 mg and reached values between 37 microg/l and 126 microg/l. The calculated AUCs were between 52 ng/ml x h and 311 ng/ml x h and the corresponding plasma elimination half-life times were between 95 min and 165 min. In all subjects plasma concentrations of pravastatin 5 hours after oral drug administration were near the detection limit of the method (5 microg/l). Intraindividually, there was only little variation in the kinetics of pravastatin. However, marked differences were encountered between the subjects studied.
CONCLUSION: The data suggest that the determination of pravastatin plasma concentrations by means of a HPLC system can be used for routine analysis of pravastatin plasma concentrations. The obtained pharmacokinetic data in healthy individuals stand in ample agreement with the results of prior studies in which the concentrations of pravastatin were determined by other more sophisticated methods.