Simultaneous determination of simvastatin, lovastatin and niacin in human plasma by LC-MS/MS and its application to a human pharmacokinetic study.

A simple, sensitive and specific LC-MS/MS method for simultaneous determination of simvastatin (SV), lovastatin (LV) and niacin (NIA) in human plasma was developed and validated on API-4000 in positive ion mode. Nevirapine was used as internal standard (IS). The assay procedure involved a simple one-step liquid-liquid extraction of SV, LV, NIA and the IS from plasma into ethyl acetate. Separation of SV, LV, NIA and the IS was achieved on an Alltima C₁₈ column with a mobile phase consisting of 5 mm ammonium acetate (pH 4.5) and acetonitrile (20:80, v/v) pumped at a flow rate of 1 mL/min. Nominal retention times obtained for SV, LV, NIA and IS were 2.12, 1.67, 0.50 and 0.65 min, respectively. The lower limits of quantification (LLOQ) for SV, LV and NIA were 0.10, 0.10 and 25.2 ng/mL, respectively. The response function was established for the range of concentrations 0.10-101 ng/mL for SV and LV, and 25.2-5020 ng/mL for NIA, with a coefficient of correlation of >0.99 for all the compounds. Method validation was performed as per FDA guidelines and the results met the acceptance criteria. The proposed method was found to be applicable to clinical studies.