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Liquid chromatographic-mass spectrometric method for the determination of fluoxetine and norfluoxetine in human plasma: application to clinical study.

Djordjevic S, Kovacevic I, Miljkovic B, Vuksanovic J, Pokrajac M

Poison Control Center, Department of Toxicological Chemistry, Military Medical Academy, Belgrade, Serbia and Montenegro.

A selective, sensitive, simple, and rapid method for the simultaneous determination of fluoxetine (FL) and norfluoxetine (nor-FL) was developed and validated, and further applied to analyze plasma samples obtained from FL-treated patients with Parkinson disease (n = 18). After one step liquid-liquid extraction with ethyl acetate, plasma samples were chromatographed on a C8 column. The mobile phase was acetate buffer and acetonitrile (40:60 v/v). Determination of FL and nor-FL was performed with MS detection in selective ion monitoring (SIM) mode, so the other components did not interfere with this assay. FL, nor-FL and flumazenil as internal standard were eluted in 6 min. Recoveries ranged from 89.7 to 96.6% and from 80.2 to 85.3% for FL and nor-FL, respectively. The limit of quantitation under described conditions was 2.5 microg/l for FL and 10 microg/l for nor-FL. The method was found to be reproducible with coefficient of variation less than 9%. The parameters of the method were found to be acceptable to enable its routine use for clinical studies. The method was employed to analyze the Parkinsonian patients' plasma samples. A great deviation in plasma concentrations of FL and nor-FL found among 18 studied patients indicates high pharmacokinetic variability of the drug. Obtained results also indicate absence of the influence of Parkinson disease on the drug disposition.

Published 25 April 2005 in Farmaco, 60(4): 345-9.
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