QUANTIFICATION OF ACITRETIN IN HUMAN PLASMA BY MICROBORE LIQUID-CHROMATOGRAPHY NEGATIVE CHEMICAL IONIZATION MASS-SPECTROMETRY

A highly sensitive liquid chromatographic-mass spectrometric procedure has been developed to quantitate plasma concentrations of acitretin, a dermatologic agent used to treat severe psoriasis. The assay utilizes the combination of normal-phase microbore high-performance liquid chromatography, negative chemical ionization mass spectrometry, selective ion monitoring and stable isotope dilution. The method has been used to measure acitretin and its metabolite, 13-cis-acitretin, over a range of 1-20 ng/ml in human plasma. The inter-assay precision was 5.3% for acitretin and 3.9% for 13-cis-acitretin, while the intra-assay precisions for acitretin and 13-cis-acitretin were 10.8 and 12.7%, respectively. Reproducibility of the assay for acitretin and 13-cis-acitretin, which was determined by the relative standard deviation of multiple analyses of the same quality assurance sample, was 5.9 and 8.1%, respectively.