HPLC-UV METHOD DEVELOPMENT FOR ATORVASTATIN CALCIUM MICRO-EMULSION DETERMINATION IN RAT PLASMA AND ITS APPLICATION TO ELUCIDATE PHARMACOKINETIC BEHAVIOR AFTER ORAL ADMINISTRATION TO RATS

A simple, rapid and validated high performance liquid chromatography (HPLC) method with UV detection for the quantification of atorvastatin Calcium microemulsions (ATC-MEs) in rat plasma was developed. The assay procedure involved chromatographic separation using a C-18 chromatographic column (250 mm × 4.6 mm, i.d., 5 μm) and a mobile phase of methanol/water (containing 0.05 % glacial acetic acid) (70:30, v/v) 1.0 mL/min and detection wavelength of 248 nm. Plasma sample (200 μL) pretreatment was based on simple deproteinization by ethanol and centrifugation. The organic layer was evaporated under N₂ gas, reconstituted with 200 μL of mobile phase, and 20 μL portions of reconstituted sample were injected onto the column. Calibration curve was linear (r ≥ 0.9854) from 0.1 to 50 mg/L. Both intra- and inter-day assay precisions that are presented through RSD were lower than 12.4% for intra-day and lower than 12.5% for inter-day assessment. This method was omitting the use of expensive solid phase extraction and time consuming liquid extraction procedures. Moreover, the present method was successfully applied to study pharmacokinetic parameters of ATC-MEs after oral administration to healthy Sprague−Dawley rats. Pharmacokinetic parameters evaluated using the analysis method were T _1/2 2.77±1.06 h, T _max 1.83±1.17 h, C _max 8.34±3.66 mg/L and AUC _0–∞ 22.07±5.44 mg· h/ L