A fully validated HPLC method for the simultaneous determination of acitretin and etretinate in plasma and its application to a pharmacokinetic study in healthy Korean subjects

OBJECTIVE: Acitretin is used for the treatment of psoriasis. The purpose of this study was to validate an HPLC method for the determination of acitretin and etretinate and to investigate the pharmacokinetic characteristics of acitretin in healthy Korean subjects. MATERIALS AND METHODS: Plasma samples or calibrators were mixed with acetonitrile and retinyl acetate (internal standard). Butanol: acetonitrile (1:1 v/v) and K2HPO4 were added later. After vortexing, 30 microl of the supernatant was injected directly into the analytical column of an HPLC system. The samples were separated by C18 reversed phase HPLC and UV detection was performed at 350 nm. Various assay performances were evaluated. RESULTS: The linearity of acitretin and etretinate was adequate up to 500 ng/ml (R2 = 0.9937 for acitretin and R2 = 0.9923 for etretinate). The accuracy was 89.5 - 113.5% and the precision was satisfactory (within-run CV, 4.4 - 15.8%; between-run CV, 3.3 - 17.4%). The LLOQ was 2 ng/ml and the stability and specificity were satisfactory. However, after storage at room temperature for 24 h under light exposure, the concentrations of acitretin and etretinate decreased by 26.0 - 66.5%. Extraction recovery was 75.1 - 91.5%. Nine healthy Korean subjects were evaluated to study the pharmacokinetics of acitretin. A single oral dose of 30 mg acitretin (Neotigason, Roche Pharmaceuticals) was given to all volunteers. The mean +/- SD pharmacokinetics of acitretin in Koreans were as follows: Cmax 148.7 +/- 93.0 ng/ml, tmax 3.2 +/- 1.3 h, t1/2 81.2 +/- 26.5 h, and AUClast 2641.9 +/- 1274.8 ng h/ml. CONCLUSION: A simple HPLC method for the simultaneous determination of acitretin and etretinate was validated, and the pharmacokinetic characteristics of acitretin in the Korean population were investigated.