DETERMINATION OF FLUVOXAMINE CONCENTRATION IN PLASMA BY REVERSED-PHASE LIQUID-CHROMATOGRAPHY

Fluvoxamine, a serotonin re-uptake inhibitor, was quantified in plasma by modifying a previously published procedure for monitoring plasma c oncentrations of tricyclic antidepressants. Alkalinized plasma samples were extracted with n-hexane/isoamyl alcohol, followed by back-extrac tion with diluted phosphoric acid. The extracts were analysed by rever sed-phase liquid chromatography using a C-18 column, with phosphate/ac etonitrile as the mobile phase. The assay was linear from 10 to 800 mu g/L. Precision studies showed within-run and day-to-day coefficients of variation to be 4.5 and 6.8%, respectively. Desipramine interfered with the detection of fluvoxamine. The assay was used to measure a tot al of 8 plasma samples from 4 alcohol-dependent patients medicated wit h fluvoxamine as an adjunct to relapse prevention psychotherapy. In th ese patients, the plasma concentrations ranged from 54 to 241 mu g/L. Dosage of fluvoxamine, duration of treatment, interval between last do sage and blood collection were associated with effects on plasma conce ntrations that were consistent with the pharmacokinetic profile of flu voxamine.