The influence of lithium on fluvoxamine therapeutic efficacy and pharmacokinetics in depressed patients on combined fluvoxamine-lithium therapy.

The influence of lithium on fluvoxamine therapeutic efficacy, plasma concentrations and pharmacokinetics was studied in 12 depressed inpatients. Six patients were on fluvoxamine monotherapy and six were on combined fluvoxamine-lithium therapy. The treatment response was determined using 17-item Hamilton Rating Scale for Depression. Blood samples were collected during 48 h after a single dose administration of 100 mg fluvoxamine, and five times at steady state after repeated doses of 100 mg fluvoxamine per day. The evaluation of 17-item Hamilton Rating Scale for Depression Scores showed a significant clinical improvement 2 and 4 weeks after the beginning of the therapy in both groups (p < 0.01). However, 2 weeks after the administration of the drug(s) had started, significant differences (p < 0.05) in efficacy between the two treatments in favour of the fluvoxamine-lithium combination were found. Plasma concentrations of fluvoxamine were measured by high-performance liquid chromatography. The comparison of the measured concentrations of fluvoxamine showed a similar course of the plasma concentration-time curves in both groups of patients. Pharmacokinetic parameters of fluvoxamine did not show any significant difference on the comparison between the groups. According to the results from this study, it is evident that lithium does not affect plasma concentrations and pharmacokinetics of fluvoxamine in depressed patients on concomitant treatment with these two drugs. However, the effect achieved with the combination was better.