Development and validation of an HPLC method to be used for simultaneous detection and quantification of different statins after ex vivo skin diffusion studies

A novel high performance liquid chromatography (HPLC) method was developed and validated to simultaneously analyse all statins currently available globally (atorvastatin, fluvastatin, lovastatin, mevastatin, pitavastatin, pravastatin, rosuvastatin, simvastatin). A Venusil XBP C₁₈(2) reverse phase column (150 x 4.6 mm) with a 5 μm particle size was used. The gradient conditions started at 25% acetonitrile, which linearly increased to 90% after 1.0 min, held at 90% until 6.5 min, and lastly, re-equilibrated to starting conditions. The mobile phase consisted of acetonitrile/water and 0.005 M (0.2%) octane sulphonic acid-Na (pH 3.5). The flow rate was set at 1.0 ml/min with a 10 μl injection volume. The HPLC method indicated linearity (R² =0.9999) within the concentration range of 0.2-206.4 μg/ml. The limit of detection (LOD) and limit of quantification (LOQ) values were found to be within the permissible criteria of ≤15% and ≤20%, respectively. Following an appropriate investigation of all the parameters for method validation, it was confirmed that the HPLC method was successfully validated and proven to be accurate to simultaneously quantify statins even in combination with other excipients used during the formulation of nano-emulsions and nano-emulgels.

UPLC-MS/MS method for the simultaneous quantification of pravastatin, fexofenadine, rosuvastatin, and methotrexate in a hepatic uptake model and its application to the possible drug-drug interaction study of triptolide

A rapid and specific UPLC-MS/MS method with a total run time of 3.5 min was developed for the determination of pravastatin, fexofenadine, rosuvastatin, and methotrexate in rat primary hepatocytes. After protein precipitation with 70% acetonitrile (containing 30% H2 O), these four analytes were separated under gradient conditions with a mobile phase consisting of 0.03% acetic acid (v/v) and methanol at a flow rate of 0.50 mL/min. The linearity, recovery, matrix effect, accuracy, precision, and stability of the method were well validated. We evaluated drug-drug interactions based on these four compounds in freshly suspended hepatocytes. The hepatic uptake of pravastatin, fexofenadine, rosuvastatin, and methotrexate at 4°C was significantly lower than that at 37°C, and the hepatocytes were saturable with increased substrate concentration and culture time, suggesting that the rat primary hepatocyte model was successfully established. Triptolide showed a significant inhibitory effect on the hepatic uptake of these four compounds. In conclusion, this method was successfully employed for the quantification of pravastatin, fexofenadine, rosuvastatin, and methotrexate and was used to verify the rat primary hepatocyte model for Oatp1, Oatp2, Oatp4, and Oat2 transporter studies. Then, we applied this model to explore the effect of triptolide on these four transporters.

Analysis of five HMG-CoA reductase inhibitors-- atorvastatin, lovastatin, pravastatin, rosuvastatin and simvastatin: pharmacological, pharmacokinetic and analytical overview and development of a new method for use in pharmaceutical formulations analysis and in vitro metabolism studies

A specific, accurate, precise and reproducible high-performance liquid chromatographic (HPLC) method was developed and validated for the simultaneous quantitation of five 3-hydroxy-3-methyglutaryl coenzyme A (HMG-CoA) reductase inhibitors, viz. atorvastatin, lovastatin, pravastatin, rosuvastatin and simvastatin, in pharmaceutical formulations and extended the application to in vitro metabolism studies of these statins. Ternary gradient elution at a flow rate of 1 mL/min was employed on an Intertisl ODS 3V column (4.6 x 250 mm, 5 microm) at ambient temperature. The mobile phase consisted of 0.01 m ammonium acetate (pH 5.0), acetonitrile and methanol. Theophylline was used as an internal standard (IS). The HMG-CoA reductase inhibitors and their metabolites were monitored at a wavelength of 237 nm. Drugs were found to be 89.6-105.6% of their label's claim in the pharmaceutical formulations. For in vitro metabolism studies the reaction mixtures were extracted with simple liquid-liquid extraction using ethyl acetate. Baseline separation of statins and their metabolites along with IS free from endogenous interferences was achieved. Nominal retention times of IS, atorvastatin, lovastatin, pravastatin, rosuvastatin and simvastatin were 7.5, 17.2, 21.6, 28.5, 33.5 and 35.5 min, respectively. The proposed method is simple, selective and could be applicable for routine analysis of HMG-CoA reductase inhibitors in pharmaceutical preparations as well as in vitro metabolism studies.

Electrochemical properties and square-wave voltammetric determination of pravastatin

The electrochemical reduction and adsorptive voltammetric behaviour of pravastatin have been studied by means of cyclic and square-wave voltammetry at a hanging mercury-drop electrode in electrolytes of different pH. Within the entire pH range (2.0-9.0) in Britton-Robinson buffer, pravastatin gave rise to a single voltammetric peak in the potential interval from -1.22 to -1.44 V, depending on pravastatin concentration. It was found that the reduction of pravastatin proceeds via a relatively stable intermediate, which is transformed to the final electroinactive product by a coupled chemical reaction or can be re-oxidized back to pravastatin. The rate of chemical transformation is controlled by the proton concentration. The electrode mechanism has the properties of a surface redox reaction. A sensitive analytical method for trace analysis of pravastatin based on the adsorptive stripping technique has been developed. The calibration plot was linear in the range 8x10(-8)-5x10(-7) mol L(-1). Application of the square-wave voltammetric method to determination of pravastatin in a pharmaceutical dosage form, without sample pretreatment, resulted in acceptable deviation from the stated concentration.

Fast analysis of pravastatin in production media

High throughput methods (high performance liquid chromatography and capillary electrophoresis) were developed to determine pravastatin in production media. The analyses were performed on particle column, monolithic column and silica capillary filled with borate buffer pH 9.3 containing 20 mM SDS. All three methods successfully separate pravastatin from interfering compounds (matrix, mevastatin and 6-epi pravastatin) and runtimes are shorter than 1 min. Solvent consumptions for methods using small particle column, monolith column and MECK were 132, 510 and 1.5 mL h(-1). The most sensitive was the method using particle column (LOD was about 10(-5) mg mL(-1)), followed by the system using monolith column (LOD was 2 x 10(-4) mg mL(-1)) and the MECK method (LOD was about 0.02 mg mL(-1)).

Determination of pravastatin in tablets by capillary electrophoresis

Pravastatin (PRA) is an inhibitor of HMG-CoA reductase enzyme, which is clinically used as a hypolipidemic agent to reduce cholesterol level. A capillary electrophoretic method for the determination of PRA in pharmaceutical tablet formulations is described. PRA and lansoprazole as an internal standard (IS) were well migrated in the background electrolyte of 10 mM borate buffer (pH 8.5) and 10% acetonitrile using a fused silica capillary. The separation was achieved by applying 27.5 kV, detecting at 200 nm and injecting the sample for 0.5 s and with an average migration time (tm) for PRA and IS of 4.7 and 3.9 min, respectively, at ambient temperature. The results were precise and repeatable for areas of the peaks and peak normalization ratio (PNPRA/PNIS). Linearity was found in the concentration range of 1.56-7.78 x 10(-5) M. Intra-day and Inter-day assays were performed and reliable results were obtained. Limit of detection and limit of quantitation were 8 x 10(-6) and 2.4 x 10(-5) M, respectively. The proposed method was successfully applied for the analysis of PRA in the pharmaceutical tablet formulation. The method proved simple, precise and fast since the analysis can be performed in less than 5 min.

[Determination of pravastatin in rat liver by RP-HPLC]

AIM

To establish a reverse-phase high performance liquid chromatographic method for the determination of pravastatin in rat liver.

METHODS

An aliquot of 5 g liver homogenates, spiked with triamcinolone acetonide (internal standard), was extracted by solid-phase extraction with Bond Elut C18 columns. Chromatography was performed using a C18 reverse-phase column with mobile phase of Na2HPO4 buffer sdution (0.035 mmol.L-1, pH 3.0)-acetonitrile (155:42).

RESULTS

The linear equation was Y = 0.1843X-4.238 x 10(-3) (gamma = 0.9934) in the range of 0.05-10 micrograms.g-1 liver. The limit of detection for pravastatin was 13 ng.mL-1 (signal-to-noise ratio of 3), and the limit of quantification for pravastatin in liver homogenate was 50 ng.g-1 liver (RSD < 20%). The average extraction recovery of pravastatin from liver at different concentrations was 80.8%, and the average inter-day precision was 11%. This procedure was applied to assay pravastatin in rat liver which were collected from Lewis rats at different times after administration of pravastatin (ig 20 mg.kg-1).

CONCLUSION

The method was sensitive and is feasible for the pharmacokinetic and distribution study of pravastatin.