A preliminary pharmacokinetic study of the enantiomers of the terfenadine acid metabolite in humans

A stereoselective and sensitive achiral/chiral method for the determination of terfenadine acid metabolite in human plasma was developed. The metabolite was separated and quantitated using an achiral chromatographic procedure with a cyano column. The mobile phase was 1 m M sodium acetate buffer (pH 4.0) and acetonitrile (25:75% v/v) at a flow rate of 2 ml/min, at ambient temperature. The stereospecific resolution was accomplished using a chiral‐AGP column and a mobile phase consisting of sodium acetate (0.01 M ): methanol (98.7:1.3% v/v), and 20 m M di‐ n ‐butylamine at a flow rate of 1.2 ml/min. The column temperature was maintained at 32°C. The eluent was monitored at 230 nm (excitation) and 300 nm (emission) with a cut‐off filter at 270 nm. This assay was used for a pharmacokinetic study in five subjects after administration of a single dose of 60 mg of terfenadine. The t ½ values of the two enantiomers were similar, but the AUC values of the (+)‐enantiomer were 2.05–2.35 times higher than those of (−)‐enantiomer. © 1994 Wiley‐Liss, Inc.