Development and validation of an LC-MS-MS method for the determination of terfenadine in human plasma

A sensitive LC-MS-MS method capable of quantifying terfenadine at levels down to 100 pg ml-1 in human plasma is reported. The method was validated over a linear range from 0.1 to 5.0 ng ml-1 using a liquid-liquid extraction with a deuterium-labelled internal standard. The between-run precision and accuracy of the calibration standards were 2.6-6.0% RSD and -2.0 to +2.2% relative error (RE). The between-run and within-run precision and accuracy of quality control samples (0.3, 1.5 and 3.5 ng ml-1) were 1.0-5.9% RSD and +1.7 to +6.3% RE. This method was applied to the analysis of human plasma samples.