Determination of Pirfenidone in Rat Plasma by LC–MS-MS and Its Application to a Pharmacokinetic Study

A simple liquid chromatography-electrospray ionization-mass spectrometric (LC–ESI–MS-MS) method was developed for determination of pirfenidone in rat plasma. After addition of phenacetin as internal standard, protein precipitation with 10% perchloric acid was employed for the sample preparation. Chromatographic separation was achieved on a C18 column, with 40: 60 (v/v) acetonitrile-0.1% formic acid as mobile phase. The assay is linear over the range 2–2,000 ng mL−1, with a lower limit of quantitation of 2 ng mL−1. The developed method was successfully applied to pharmacokinetic studies of pirfenidone in rats following single oral administration dose of 15 mg kg−1.