Quantification of Teprenone in Human Plasma by HPLC Coupled to Mass Spectrometry: Application to a Bioequivalence Study

A rapid, sensitive, and specific method has been developed for quantification of teprenone (TEP) in human plasma. The analytes were isolated from plasma by liquid–liquid extraction with t-butyl methyl ether. The extracts were analyzed by high-performance liquid chromatography coupled to mass spectrometry (HPLC–MS); gefarnate was used as internal standard (IS). HPLC separation of the analytes was performed on a C18 column with 1:54:45 (v/v) 1% aqueous acetic acid–methanol–acetonitrile as mobile phase; the flow rate was 0.2 mL min−1. The compounds were ionized by atmospheric-pressure chemical ionization (APCI). Calibration plots for TEP were linear in the range 20.0–2000.0 ng mL−1; correlation coefficients were >0.9981. The average extraction efficiency for TEP was >67%, method recovery was >95%, the limit of detection (LOD) was 1.0 ng mL−1, and the intraday and interday coefficients of variation were <7%. This HPLC–MS procedure was used to assess the bioequivalence of TEP tablet and capsule formulations. A single 150-mg dose of each formulation was administered to 18 healthy male volunteers. The study was conducted using an open, randomized, two-period crossover design with a 1-week wash-out interval. Because the 90% CI for Cmax and the ratios of the AUCs were all within the 80–125% range stipulated by the US Food and Drug Administration, it was concluded that the TEP tablet and capsule formulations were bioequivalent in terms of rate and extent of absorption.