n the single-dose crossover study, mean Cmax was 38% lower and relative bioavailability was 84% for LUVOX CR Capsules versus immediate-release fluvoxamine maleate tablets.
In a multiple-dose proportionality study, LUVOX CR Capsules were administered over a dose range of 100 mg/day to 300 mg/day to 20 healthy volunteers. Steady-state plasma concentrations were achieved within a week of dosing. Mean maximum plasma concentrations were 47 ng/mL, 161 ng/mL, and 319 ng/mL, respectively, at the 100 mg, 200 mg, and 300 mg administered dose levels. Fluvoxamine exhibited nonlinear pharmacokinetics producing disproportionately higher concentrations over the dose range. The AUC and Cmax values increased 5.7-fold following the 3-fold increase in dose from 100 mg to 300 mg.
Food caused the mean AUC and Cmax of fluvoxamine to increase only slightly; therefore, administration of LUVOX CR Capsules with food does not significantly affect the absorption of fluvoxamine.
Distribution/Protein Binding: The mean apparent volume of distribution for fluvoxamine is approximately 25 L/kg, suggesting extensive tissue distribution.
Approximately 80% of fluvoxamine is bound to plasma protein, mostly albumin, over a concentration range of 20 to 2000 ng/mL.
Metabolism: Fluvoxamine maleate is extensively metabolized by the liver; the main metabolic routes are oxidative demethylation and deamination. Nine metabolites were identified following a 5 mg radiolabelled dose of fluvoxamine maleate, constituting approximately 85% of the urinary excretion products of fluvoxamine. The main human metabolite was fluvoxamine acid which, together with its N-acetylated analog, accounted for about 60% of the urinary excretion products. A third metabolite, fluvoxethanol, formed by oxidative deamination, accounted for about 10%. Fluvoxamine acid and fluvoxethanol were tested in an in vitro assay of serotonin and norepinephrine reuptake inhibition in rats; they were inactive except for a weak effect of the former metabolite on inhibition of serotonin uptake (1-2 orders of magnitude less potent than the parent compound). Approximately 2% of fluvoxamine was excreted in urine unchanged (see DRUG INTERACTIONS [7]).
Elimination: Following a 14C-labelled oral dose of fluvoxamine maleate (5 mg), an average of 94% of drug-related products was recovered in the urine within 71 hours.
After administration of a 100 mg, single oral dose of LUVOX CR Capsules, the mean plasma half-life of fluvoxamine in healthy male and female volunteers was 16.3 hours.
Gender: In a study with 15 male and 13 female healthy volunteers who were administered LUVOX CR Capsules 100 mg, AUC and Cmax of fluvoxamine were increased by approximately 60% in females compared to males. There were no differences in the elimination half-life between males and females.
Elderly Subjects: In a study using immediate-release fluvoxamine maleate tablets at 50 mg and 100 mg and comparing elderly (ages 66-73 years) and young subjects (ages 19-35 years), mean maximum plasma concentrations in the elderly were 40% higher. The multiple-dose elimination half-life of fluvoxamine was 17.4 hours and 25.9 hours in the elderly compared to 13.6 hours and 15.6 hours in the young subjects at steady state for 50 mg and 100 mg doses, respectively.
In elderly patients administered immediate-release fluvoxamine maleate tablets, the clearance of fluvoxamine was reduced by about 50%; therefore, LUVOX CR Capsules should be slowly titrated during init |
