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Determination of serum reboxetine enantiomers in patients on chronic medication with racemic reboxetine.

The chiral compound reboxetine is used as a selective noradrenaline reuptake inhibitor (NARI) for the treatment of major depressive disorders. The pharmacokinetic variability of the enantiomers of the drug (S,S- and R,R-reboxetine) was studied using stereoselective high-performance liquid chromatography with mass spectrometric detection in a controlled clinical monotherapy situation (trial I) and a naturalistic clinical setting (trial II). Trial I included patients receiving racemic reboxetine as 6-month monotherapy for treatment of major depressive disorder. Trough level serum samples in steady state were analyzed for the concentration of the reboxetine enantiomers in study weeks 4, 12, and 24. In a therapeutic drug monitoring setting (trial II), 47 patients on doses ranging from 4 to 16 mg daily, including much polypharmacy, trough level steady-state serum samples were analyzed by the same bioanalytical method. Data from trials I and II were assessed to determine the inter- and intraindividual pharmacokinetic outcomes. The results showed that the median S,S/R,R ratio in steady state was 0.5 and ranged from 0.22 to 0.88. It was also shown that women have an approximately 30% higher S,S/R,R ratio than men. The S,S/R,R ratios of reboxetine were not found to correlate with reboxetine concentrations. To investigate the NARI activity of a circulating serum reboxetine concentration, a recalculation of the determined enantiomeric concentrations to previously demonstrated experimental NARI potencies of the drug enantiomers was performed. This partly novel concept of estimating pharmacodynamic activity showed that the serum NARI activity in women tended to be higher than in men at a given reboxetine concentration. In conclusion, the variability in the NARI activity per nmol/L reboxetine and the variability in the concentration outcome of the reboxetine enantiomers may justify the use of enantioselective drug monitoring in the clinic. The gender aspects of the drug have to be further assessed.

Adrenergic Uptake Inhibitors↗

Clinical pharmacokinetics of reboxetine, a selective norepinephrine reuptake inhibitor for the treatment of patients with depression.

Reboxetine is a novel selective norepinephrine inhibitor that has been evaluated in the treatment of patients with depression. Reboxetine is a racemic mixture, and the (S,S)-(+)-enantiomer appears to be the more potent inhibitor. However, the ratio of the areas under the concentration-time curves of the (S,S)-(+)- and (R,R)-(-)-enantiomers in vivo is approximately 0.5. There is no evidence for chiral inversion. Differences in the clearances of the 2 enantiomers may be explained by differences in protein binding. The pharmacokinetics of reboxetine are linear following both single and multiple oral doses up to a dosage of 12 mg/day. The plasma concentration-time profile following oral administration is best described by a 1-compartment model, and the mean half-life (approximately 12 hours) is consistent with the recommendation to administer the drug twice daily. Reboxetine is well absorbed after oral administration. The absolute bioavailability is 94.5%, and maximal concentrations are generally achieved within 2 to 4 hours. Food affects the rate, but not the extent, of absorption. The distribution of reboxetine appears to be limited to a fraction of the total body water due to its extensive (>97%) binding to plasma proteins. The primary route of reboxetine elimination appears to be through hepatic metabolism. Less than 10% of the dose is cleared renally. A number of metabolites formed through hepatic oxidation have been identified, but reboxetine is the major circulating species in plasma. In vitro studies show that reboxetine is predominantly metabolised by cytochrome P450 (CYP) 3A4; CYP2D6 is not involved. Reboxetine plasma concentrations are increased in elderly individuals and in those with hepatic or renal dysfunction, probably because of reduced metabolic clearance. In these populations, reboxetine should be used with caution, and a dosage reduction is indicated. Ketoconazole decreases the clearance of reboxetine, so that the dosage of reboxetine may need to be reduced when potent inhibitors of CYP3A4 are coadministered. Quinidine does not affect the in vivo clearance of reboxetine, confirming the lack of involvement of CYP2D6. There is no pharmacokinetic interaction between reboxetine and lorazepam or fluoxetine. Reboxetine at therapeutic concentrations has no effect on the in vitro activity of CYP1A2, 2C9, 2D6, 2E1 or 3A4. The lack of effect of reboxetine on CYP2D6 and CYP3A4 was confirmed by the lack of effect on the metabolism of dextromethorphan and alprazolam in healthy volunteers. Thus, reboxetine is not likely to affect the clearance of other drugs metabolised by CYP isozymes.

Administration, Oral↗

Ketoconazole inhibits the clearance of the enantiomers of the antidepressant reboxetine in humans.

BACKGROUND: Ketoconazole is a potent inhibitor of the cytochrome P450 3A4 enzyme. Reboxetine, a selective norepinephrine reuptake inhibitor, is metabolized by cytochrome P450 3A4. The potential interaction of reboxetine with this representative from the azole derivative class was examined. METHODS: Eleven healthy volunteers received (1) 4 mg reboxetine orally on the second day of a 5-day regimen of 200 mg ketoconazole once daily and (2) 4 mg reboxetine orally in a crossover design. Plasma concentrations of reboxetine enantiomers [R,R(-)-reboxetine and the more active S,S(+)-reboxetine] were measured by high-performance liquid chromatography-tandem mass spectrometry. Effects of ketoconazole on enantiomer pharmacokinetics were assessed by ANOVA. RESULTS: Ketoconazole increased R,R(-)-reboxetine and S,S(+)-reboxetine mean area under the plasma concentration-time curves (AUC) by 58% and 43%, respectively (P < .02). Oral clearance of both enantiomers was consequently decreased 34% and 24%, respectively, by ketoconazole (P < .005). Ketoconazole did not significantly affect maximal plasma concentrations (P > .1). Mean terminal half-life after administration of ketoconazole (21.5 hours and 18.9 hours) was significantly longer than after reboxetine alone (14.8 hours and 14.4 hours; P < or = .005). The AUC ratio for R,R(-)-reboxetine to S,S(+)-reboxetine was reduced by ketoconazole administration (2.76 after ketoconazole versus 2.39; P < .003). CONCLUSION: Ketoconazole decreases clearance of both reboxetine enantiomers. Although the adverse effect profile for reboxetine was not altered by ketoconazole, the results of this study suggest that caution should be used and that a reduction in reboxetine dose should be considered when the two are coadministered.

Adult↗

Reboxetine: attenuation of intravenous nicotine self-administration in rats.

The ability of reboxetine, a selective inhibitor of the norepinephrine transporter and noncompetitive antagonist at neuronal nicotinic receptors, to alter nicotine self-administration in rats was compared with that of mecamylamine, a classical noncompetitive antagonist at nicotinic receptors. The ability of reboxetine to alter sucrose-maintained responding was also examined to assess the specificity of the effect on nicotine self-administration. Rats were trained on a fixed ratio 5 schedule to self-administer nicotine (0.02 mg/kg/infusion i.v.) or to respond for sucrose pellets. Upon reaching a stable baseline, rats were pretreated 15 min before the session with vehicle, reboxetine (racemic), (+)-(S,S)-reboxetine (0.3-30 mg/kg s.c.) or mecamylamine (0.5-4 mg/kg s.c). To assess the effect of repeated administration, reboxetine (5.6 mg/kg) was injected once daily for 14 consecutive sessions before either nicotine self-administration or sucrose-maintained responding. Specificity was further assessed by examining the ability of repeated administration of reboxetine (5.6 mg/kg) to alter nicotine-induced hyperactivity (0.8 mg/kg). Reboxetine, (+)-(S,S)-reboxetine, and mecamylamine dose dependently decreased nicotine self-administration by ~60%, whereas reboxetine and (+)-(S,S)-reboxetine decreased sucrose-maintained responding to a lesser extent (~20%). Repeated administration of reboxetine (5.6 mg/kg) decreased nicotine self-administration and sucrose-maintained responding across the 14 sessions, suggesting that tolerance did not develop to these effects of reboxetine. Additionally, reboxetine did not alter baseline locomotor activity, indicating that the decrease in operant responding for nicotine and sucrose was not the result of a nonspecific decrease in activity. The reboxetine-induced decrease in nicotine self-administration and sucrose-maintained responding may be the result of inhibition of norepinephrine transporters and/or neuronal nicotinic receptor function.

Adrenergic Uptake Inhibitors↗

Reboxetine: a review of antidepressant tolerability.

The tolerability of reboxetine was evaluated in 2613 adult (aged 18-65 years) or elderly (aged > 65 years) patients with depressive illness treated with reboxetine, comparator agents or placebo, who entered both short- and long-term, controlled and uncontrolled clinical trials. The reboxetine adverse-event profile in acute depression was established by comparison with placebo in 746 patients. Overall, 69% of 373 patients treated with reboxetine experienced adverse events compared with 57% of 373 patients in the placebo group. The majority of adverse events were moderate in severity, and discontinuation because of adverse events was low and comparable in both the reboxetine (8%) and the placebo (7.5%) group. When compared with imipramine, reboxetine was better tolerated. Most side-effects were less common in the reboxetine than the imipramine cohort, and fewer patients receiving reboxetine (10% in adult patients; 11% in elderly patients) discontinued treatment because of adverse events than those receiving imipramine (14% in adult patients; 16% in elderly patients). Compared with fluoxetine, the total frequency of adverse events was similar in reboxetine-treated patients (67%) and fluoxetine-treated patients (65%). In the fluoxetine group, 7% discontinued because of adverse events compared to 12% in the reboxetine group and 12% in the corresponding placebo group. In a 12-month placebo-controlled study, discontinuation because of adverse events in both groups was low (reboxetine 4%; placebo 1%), and the total frequency of adverse events was only marginally higher with reboxetine (28%) than with placebo (23%). Overall, no consistent changes were found in laboratory tests or electrocardiogram recordings and there was no indication of withdrawal symptoms upon abrupt reboxetine discontinuation. Reboxetine, a novel selective noradrenaline reuptake inhibitor, is well tolerated by adults and the elderly during short- and long-term treatment for depression.

Adrenergic Uptake Inhibitors↗

Effects of reboxetine on sympathetic neuroeffector transmission in rabbit carotid artery.

The effect of reboxetine on sympathetic neuroeffector transmission in rabbit isolated carotid artery was examined. Reboxetine (10-8-3 x 10-6 M) and cocaine (10-6-3 x 10-5 M), but not desipramine (10-8-3 x 10-7 M), increased contractions evoked by electrical field stimulation. At higher concentrations, reboxetine (10-4 M), cocaine (3 x 10-4 M), and desipramine (3 x 10-7-10-5 M) inhibited the neurogenic contractions. The enhancement seen with reboxetine and cocaine was partially reversible, whereas the inhibition was readily reversible. Reboxetine (10-7 M) and cocaine (10-5 M) prevented the inhibitory action of bretylium (10-6 M). Reboxetine (10-8-10-5 M), desipramine (10-7-10-4 M), and cocaine (10-6-10-5 M) increased the stimulation-evoked [3H]norepinephrine release. Pargyline (5 x 10-4 M) augmented the facilitatory effect of reboxetine (3 x 10-9-10-6 M) and cocaine (10-7-3 x 10-5 M). Reboxetine (10-8-10-6 M), desipramine (10-8-10-6 M), and cocaine (3 x 10-8-10-5 M) reduced the [3H]norepinephrine (10-8 M) uptake. Reboxetine (10-7 M) and cocaine (10-5-2 x 10-4 M) enhanced the contractions evoked by phenylephrine and norepinephrine. Higher concentrations of reboxetine antagonized the contractions. Reboxetine (10-5-6 x 10-5 M) antagonized the contractions evoked by potassium. The contractions evoked by tyramine (3 x 10-6-10-3 M) was reduced by reboxetine (3 x 10-8-10-6 M) and by cocaine (10-7-10-5 M). We conclude that reboxetine inhibits the membrane amine pump (uptake-1) in the terminals of postganglionic adrenergic neurons in a cocaine-like manner.

Animals↗

Reboxetine: additional benefits to the depressed patient.

Reboxetine is a new selective noradrenaline reuptake inhibitor that has been shown to be effective in both the short-(4-8 weeks) and long-term (up to 12 months) treatment of depression. Four positive placebo-controlled studies showed reboxetine to have significant antidepressant efficacy; the response rate (> or = 50% decrease in HAM-D total score) with reboxetine ranging from 56-74%. Comparator-controlled trials showed reboxetine to be at least as efficacious as imipramine and desipramine in both adults and elderly patients. Reboxetine is also as effective as fluoxetine in the overall depressed population. However, subset analysis showed reboxetine to be significantly superior to fluoxetine in severely depressed patients. Reboxetine also showed significant advantages over fluoxetine in terms of social functioning, positively affecting patients' self perception and motivation towards action. The therapeutic effect of reboxetine is maintained for at least up to 1 year. During long-term therapy, 78% of patients receiving reboxetine were in remission at last assessment compared with only 45% of patients in the placebo group. Fewer reboxetine-treated patients relapsed (22%) compared with those receiving placebo (56%). In summary, reboxetine is effective in both the short- and long-term treatment of depression, and is at least as efficacious as traditional tricyclic antidepressant drugs and selective serotonin reuptake inhibitors. The additional benefits offered by reboxetine to the depressed patient include effective long-term treatment, efficacy in all grades of depression (including severe cases) and, importantly, specific advantages on social functioning. These additional benefits make reboxetine a favourable choice in the management of depression.

Adrenergic Uptake Inhibitors↗

Pharmacokinetics of reboxetine in healthy volunteers with different ethnic descents.

RATIONALE: Ethnicity can affect the pharmacokinetics and pharmacodynamics of psychopharmacologic drugs. OBJECTIVES: Reboxetine disposition differences among Asians, blacks, and Caucasians were examined. METHODS: Healthy subjects (12 Asians, 12 blacks, 12 Caucasians) received a single oral dose of one 4-mg reboxetine tablet in an open label, parallel study design. Plasma concentrations of reboxetine enantiomers [R,R(-) reboxetine and predominantly active S,S(+) reboxetine] were quantified using HPLC-MS-MS. Plasma unbound fractions of reboxetine enantiomers were evaluated by equilibrium dialysis. Ethnic group effects on pharmacokinetic parameters were assessed by ANOVA. RESULTS: Mean S,S(+) reboxetine CLPO for blacks was significantly greater, compared to Asians and Caucasians (154+/-82 ml/min, 101+/-19 ml/min and 101+/-18 ml/min, respectively). Mean S,S(+) reboxetine free fractions (fu) were significantly greater for Asians and blacks, compared to Caucasians (3.04+/-1.28%, 2.89+/-0.69%, and 1.99+/-0.58%, respectively). S,S(+) Reboxetine unbound clearance (CLu) was significantly less for Asians, compared to blacks and Caucasians (3742+/-1468 ml/min, 5187+/-2027 ml/min, and 5294+/-1163 ml/min, respectively). S,S(+) Reboxetine mean unbound AUC (AUCu) in these groups were 20.2+/-7.1 ng.h/ml, 14.6+/-5.1 ng.h/ml, and 13.2+/-3.2 ng.h/ml, respectively. AUCu was significantly greater for Asians. CLu and AUCu did not differ significantly between blacks and Caucasians. Ethnic effects of R,R(-) reboxetine were similar to those observed for S,S(+) reboxetine. CONCLUSIONS: The AUCu difference between Asian and black and Caucasian subjects was modest. Tolerability differences among groups were not observed. No dosage adjustment is necessary for Asians or blacks.

Adrenergic Uptake Inhibitors↗

Studies on the acute and chronic effects of reboxetine on extracellular noradrenaline and other monoamines in the rat brain.

1 The effect of reboxetine, a novel antidepressant drug that potently and selectively inhibits neuronal noradrenaline (NA) uptake, on brain extracellular monoamines was studied by microdialysis. 2 Fifteen mg kg-1 i.p. reboxetine raised extracellular NA in the frontal cortex (by 242%) and dorsal hippocampus (by 240%). 3 Idazoxan (1 mg kg-1 s.c.), given 60 min after 15 mg kg-1 reboxetine, markedly potentiated the effect on extracellular NA in the frontal cortex (by 1580%) and dorsal hippocampus (by 1360%), but had no effect by itself. 4 Twenty-four hours after the last injection of a chronic schedule (15 mg kg-1 i.p. once daily for 14 days) reboxetine had no effect on basal extracellular concentrations of NA in the dorsal hippocampus and a challenge dose of reboxetine (15 mg kg-1) raised extracellular NA similarly in rats treated chronically with reboxetine (by 353%) and saline (by 425%). 5 Ten and 20 microg kg-1 i.p. clonidine dose-dependently reduced hippocampal extracellular NA similarly in rats given chronic reboxetine (by 32% and 57%) and saline (by 42% and 56%). 6 Extracellular concentrations of dopamine and 5-HT in the striatum were similar in rats treated chronically with reboxetine and saline. A challenge dose of reboxetine (15 mg kg-1) had no effect on striatal extracellular dopamine and slightly increased striatal extracellular 5-HT to a similar extent in rats treated chronically with reboxetine (by 137%) and saline (by 142%). 7 The results suggest that combining reboxetine with an alpha2-adrenoceptor antagonist may facilitate its antidepressant activity. Repeated treatment confirmed that reboxetine is fairly selective for the noradrenergic system but provided no evidence of adaptive changes in that system that could facilitate its effect on extracellular NA.

Adrenergic alpha-Agonists↗

Reboxetine: a pharmacologically potent, selective, and specific norepinephrine reuptake inhibitor.

BACKGROUND: Reboxetine is a potent antidepressant, with efficacy comparable to that of imipramine, desipramine, and fluoxetine, and has improved side-effect profile. The basis of its efficacy and improved tolerability is sought through studies of reboxetine in a number of pharmacological models of depression. METHODS: Pharmacological selectivity for uptake systems was defined by uptake and binding assays for the three monoamine uptake sites. Specificity was determined in 39 different receptor and 6 enzyme assays. In vivo selectivity was defined by measurement of neuronal firing rates in the locus coeruleus, dorsal raphe, and substantia nigra. Reserpine-induced blepharospasm and hypothermia, clonidine-induced hypothermia, defined reboxetine's in vivo pharmacology. Reboxetine's antidepressant potential was evaluated behaviorally by the tail-suspension test, forced swimming, and the DRL72 operant responding test. RESULTS: Reboxetine is a potent, selective, and specific norepinephrine reuptake inhibitor (selective NRI) as determined by both in vitro and in vivo measurements. Unlike desipramine or imipramine, reboxetine has weak affinity (Ki > 1,000 nmol/L)for muscarinic, histaminergic H1, adrenergic alpha1, and dopaminergic D2 receptors. In vivo action of reboxetine is entirely consistent with the pharmacological action of an antidepressant with preferential action at the norepinephrine reuptake site. Reboxetine showed an antidepressant profile in all tests of antidepressant activity used. Significant decreases in immobility were observed in the tail suspension test and behavioral despair test. Increased efficiency in responding was observed in the DRL72 test. CONCLUSIONS: Reboxetine is a potent, selective, and specific noradrenergic reuptake inhibitor. It has a superior pharmacological selectivity to existing tricyclic antidepressants and selective serotonin reuptake inhibitors when tested in a large number of in vitro and in vivo systems. Given the pharmacological profile, reboxetine is expected to be a selective and potent tool for psychopharmacological research. The use of reboxetine in the clinic will also help clarify the role norepinephrine plays in depression.

Adrenergic Uptake Inhibitors↗

Mirtazapine decreases stimulatory effects of reboxetine on cortisol, adrenocorticotropin and prolactin secretion in healthy male subjects.

Reboxetine is a selective noradrenaline reuptake inhibitor, whereas mirtazapine acts as an antagonist at noradrenergic alpha(2), serotonin (5-HT(2)), 5-HT(3) and histamine H(1) receptors. In a former study we could demonstrate an inhibitory impact of mirtazapine on cortisol secretion. In the present investigation, the influence of combined administration of 15 mg mirtazapine and 4 mg reboxetine on the cortisol (COR), adrenocorticotropin (ACTH), growth hormone (GH), and prolactin (PRL) secretion was examined in 12 healthy male subjects, compared to reboxetine alone (4 mg). In a randomized order, the subjects received reboxetine (4 mg) alone or the combination of reboxetine (4 mg) and mirtazapine (15 mg) at 8:00 a.m. on two different days. After insertion of an intravenous catheter, blood samples were drawn 1 h prior to the administration of single reboxetine or the combination (reboxetine and mirtazapine), at time of administration, and during the time of 5 h thereafter in periods of 30 min. Serum concentrations of COR, GH, and PRL as well as plasma levels of ACTH were determined in each blood sample by means of double antibody RIA, fluoroimmunoassay and chemiluminescence immunometric assay methods. The area under the curve (AUC) was used as parameter for the COR, ACTH, GH, and PRL response. For statistical evaluation, the Wilcoxon signed-ranks test was performed. There was a pronounced stimulation of COR, ACTH, GH, and PRL concentrations after single administration of reboxetine. When reboxetine was given in combination with mirtazapine, a significant reduction of the COR, ACTH, and PRL stimulation was observed whereas GH secretion patterns remained unchanged, compared to single administration of reboxetine. Apparently, the stimulatory effects of reboxetine on pituitary hormone secretion via noradrenergic mechanisms are counteracted in part by the alpha(2)-blocking properties of mirtazapine and its inhibitory influence on cortisol secretion.

Adrenergic Uptake Inhibitors↗

Absolute bioavailability of reboxetine enantiomers and effect of gender on pharmacokinetics.

The absolute bioavailability of reboxetine enantiomers was assessed in six male and six female volunteers. In a two-way crossover study, subjects received 1.0 mg reboxetine orally and 0.3 mg reboxetine as an intravenous bolus. The R,R(-) and S,S(+) enantiomers in serial plasma and urine samples were determined by a validated LC-MS-MS method. There were no significant differences between treatments for clearance or dose-corrected AUC(0-infinity) values. The absolute bioavailability was 0.919 and 1.02 for R,R(-) reboxetine and S,S(+) reboxetine, respectively. A secondary objective of the study was to assess gender effects on pharmacokinetics of the enantiomers. Significant differences in volume of distribution between genders were observed, but differences in weight-corrected volumes were not significant. Weight-corrected systemic clearance and oral clearance tended to be lower in males, but this difference reached statistical significance only for weight-corrected oral clearance of R,R(-) reboxetine. C(max) after oral administration was 40 and 48% higher in women than men for R,R(-) reboxetine and S,S(+) reboxetine, respectively. These results indicate that reboxetine enantiomers are well absorbed after oral administration and that little first-pass metabolism occurs. There are no clinically significant effects of gender on the pharmacokinetics of reboxetine enantiomers.

Administration, Oral↗

Hemodynamic effects of reboxetine in healthy male volunteers.

BACKGROUND: Reboxetine [(R,S)-2[(R,S)-alpha-(2-ethoxyphenoxy)benzyl]morpholine methanesulfonate] is a racemic compound that consists of equal proportions of R,R- and S,S-enantiomers. This study investigated the hemodynamic effects of reboxetine and the R,R-enantiomer compared with placebo in volunteers. The pharmacokinetics of reboxetine and its enantiomers were also investigated in the study. METHODS: Nine healthy, male volunteers received single doses of 4 mg reboxetine, 2 mg R,R-enantiomer, and placebo at weekly intervals. Reboxetine and the R,R-enantiomer were well tolerated in all volunteers. RESULTS: The heart rates of patients in the supine and standing positions were increased after reboxetine administration compared with the R,R-enantiomer (P < .05, except supine heart rate at 6 hours) and placebo (P < .05). Supine systolic and diastolic blood pressure was also increased by 3 +/- 4 and 1 +/- 4 mm Hg, respectively, after reboxetine compared with R,R-enantiomer (-2 +/- 4 and -4 +/- 3 mm Hg) and placebo (-4 +/- 4 and -4 +/- 4 mm Hg) administration. The systolic and diastolic blood pressure measurements for subjects while standing did not differ significantly among treatments. There was no significant difference between the maximum plasma concentration, mean time to maximum plasma concentration, plasma half-life, or area under the plasma concentration-time curve (AUC) of the R,R-enantiomer after reboxetine or R,R-enantiomer administration. The ratio of the mean AUC values for the R,R- and S,S-enantiomers was 2.1. CONCLUSION: These findings suggest that the S,S-enantiomer is responsible for the hemodynamic effects of reboxetine in humans. Increases in supine blood pressure after reboxetine administration may be interpreted as regression to the mean value and not caused by any treatment effect.

Adrenergic Uptake Inhibitors↗

Noradrenergic lesions differentially alter the antidepressant-like effects of reboxetine in a modified forced swim test.

The novel antidepressant reboxetine is a selective norepinephrine reuptake inhibitor. In this study, the antidepressant-like effects of reboxetine were characterized in a modified rat forced swim test. Further, in order to investigate the role of the locus coeruleus and lateral tegmental noradrenergic systems in the mediation of reboxetine's effects, the impact of different chemical lesions of these two pathways was examined on the behavioral responses induced by reboxetine in the forced swim test. Reboxetine (5-20 mg/kg, s.c.) dose-dependently decreased immobility and swimming behavior in the forced swim test while it simultaneously increased climbing behavior. These effects were similar to those previously demonstrated with tricyclic antidepressants and are indicative of reboxetine's effects on the noradrenergic system. Discrete local injections of the neurotoxin 6-hydroxydopamine were employed to lesion the ventral noradrenergic bundle arising from cells located in the lateral tegmentum. This resulting lesion completely prevented reboxetine (10 mg/kg, s.c.)-induced decreases in immobility and increases in climbing behavior, demonstrating that an intact ventral noradrenergic bundle is required for the manifestation of reboxetine-induced antidepressant-like behavior in the test. In contrast, lesions of the dorsal noradrenergic bundle which consists of neurons arising from the nucleus locus coereleus, were achieved by systemic pretreatment with the selective noradrenergic neurotoxin N-(2-chloroethyl)-N-2-bromobenzylamine (DSP-4; 50 mg/kg, i.p.). The ability of reboxetine (10 mg/kg, s.c.) to increase climbing and decrease immobility was augmented by DSP-4 pretreatment. Furthermore, neither lesions of the dorsal noradrenergic bundle nor the ventral noradrenergic bundle altered baseline immobility scores in the forced swim test. Taken together, these data suggest that forebrain regions innervated by these two distinct noradrenergic pathways exert opposing influences on the behavioral response to reboxetine in the rat forced swim test.

Animals↗

Double-blind, placebo-controlled study with reboxetine in inpatients with severe major depressive disorder.

The efficacy and tolerability of reboxetine, a unique selective noradrenaline reuptake inhibitor, were compared with those of placebo in a 6-week, randomized, double-blind study of hospitalized patients with a DSM-III-R diagnosis of major depressive disorder. Fifty-two patients (25 in the placebo group, 27 in the reboxetine group) were included in the efficacy analysis. Sixteen (64%) of those in the placebo group and four (15%) in the reboxetine group were withdrawn during the study because of lack of efficacy. Improvement in the mean Hamilton Rating Scale for Depression (HAM-D) total score at last assessment was significantly greater in the reboxetine group than in the placebo group (p < 0.001). Similarly, the response rate to treatment, defined as > or =50% reduction in HAM-D total score, was 74% for patients who received reboxetine compared with 20% for those who received placebo (p < 0.001). A significantly greater response with reboxetine than with placebo was seen as early as day 10 of treatment (p = 0.006). The therapeutic efficacy of reboxetine was substantiated by improvement in mean scores on the Zung Self-Rating Scale and on the Clinical Global Impression Severity of Illness and Global Improvement scales. Reboxetine was well tolerated, and only one patient in each group withdrew because of adverse events. Dry mouth, insomnia, blurred vision, sweating, and constipation were recorded more frequently in the reboxetine group than in the placebo group. There was a tendency toward orthostatic changes in the systolic blood pressure, but this was not clinically significant. This study demonstrated that reboxetine is significantly more effective than placebo in the treatment of hospitalized patients with severe major depressive disorder and is well tolerated.

Adolescent↗

Efficacy and tolerability of reboxetine compared with citalopram: a double-blind study in patients with major depressive disorder.

The objective of this study was to compare efficacy and tolerability of the selective noradrenaline reuptake inhibitor reboxetine with the selective serotonin reuptake inhibitor citalopram, in the treatment of major depressive disorder (MDD). In total, 357 outpatients with MDD were randomized to treatment with reboxetine 8-10 mg or citalopram 20-40 mg per day during 24 weeks. Primary end-point was change from baseline in the Hamilton Depression Rating Scale (HAM-D, 21 items). Sexual function/dysfunction was measured by the Sexual Function scale (SF). Observed case analysis showed that both treatments yielded a gradual reduction of HAM-D scores: reboxetine with -21.4 and citalopram with -22.1 points (NS). LOCF analysis showed a greater reduction of the HAM-D scores with citalopram compared with reboxetine (-19.6 vs. -17.8; P = 0.034). The response rate was 90.3% for reboxetine and 92.7% for citalopram (NS). The most common side effect in the reboxetine group was dry mouth, and in the citalopram group sexual dysfunction. At week 24, anorgasmia was reported by 5.9% of the sexually active women in the reboxetine group vs 39% in the citalopram group. The dropout number was 91 in the reboxetine group, and 54 in the citalopram group. To summarize, both treatments gave a satisfactory antidepressant effect. The side effect profile differed between the groups, with a notably high prevalence of sexual dysfunctions in the citalopram group. The high number of dropouts in the reboxetine group, is considered as a result of the non-titration starting dose of 8 mg reboxetine per day, which gave a high incidence of early side-effects.

Adolescent↗

Resolution of sexual dysfunction during double-blind treatment of major depression with reboxetine or paroxetine.

The selective noradrenaline re-uptake inhibitor reboxetine may have advantages over the selective serotonin re-uptake inhibitors fluoxetine and citalopram, in effects on sexual function and satisfaction. The effects of reboxetine and paroxetine on sexual function were compared by examining data from the UK centres in an international double-blind flexible-dose parallel-group multi-centre randomized controlled trial of acute treatment of patients with DSM-IV major depression. Patients were randomly assigned to receive reboxetine (4 mg b.d.) or paroxetine (20 mg mane) using a double-dummy technique to preserve the blind. The dosage could be increased at day 28 (to reboxetine 4 mg mane, 6 mg nocte; or paroxetine 20 mg b.d.). Antidepressant efficacy was assessed by the 21-item Hamilton Rating Scale for Depression (HAM-D) and Clinical Global Impression Scale for Severity (CGI-S) at all study visits, and the Clinical Global Impression of Improvement (CGI-I) at each visit after randomization. Sexual function and satisfaction was assessed by visual analogue scale (VAS) items of the Rush Sexual Inventory completed at baseline and days 28 and 56. There were no significant differences between groups in demographic or clinical features at baseline. There was a gradual reduction in severity of depressive symptoms (reboxetine, 14.3; paroxetine, 12.0: observed case analysis), with no significant differences between groups. There were significant differences (p 0.05), with advantages for reboxetine, at Week 4 and Week 8 on the VAS item assessing ability to become sexually excited, and non-significant trends with advantages for reboxetine, in frequency of sexual thoughts at Week 4 (p 0.05) and Week 8 (p 0.08); and in desire to initiate sexual activity at Week 4 (p 0.09). Exclusion of patients who had ever experienced sexual dysfunction with any medication prior to participation in this study (n 10) reduced the statistical significance of the findings, although there were still numerical advantages for reboxetine. Sexual function and satisfaction in depressed patients improves during double-blind acute treatment with reboxetine or paroxetine, but this improvement is greater and more rapid with reboxetine.

Adult↗

Reboxetine, a unique selective NRI, prevents relapse and recurrence in long-term treatment of major depressive disorder.

BACKGROUND: The long-term efficacy and tolerability of the antidepressant reboxetine, a unique selective norepinephrine reuptake inhibitor (selective NRI), were assessed in an international study. METHOD: Two hundred eighty-three patients with recurrent DSM-III-R major depression who responded to 6 weeks of reboxetine treatment (> or =50% decrease in Hamilton Rating Scale for Depression [HAM-D] total score) were randomly assigned to receive reboxetine or placebo for 46 weeks in a double-blind phase. Relapse (> or =50% increase in HAM-D total score and/or a HAM-D total score > or =18) rate was the principal assessment criterion and included patients who experienced relapse or recurrence. Only patients who remained relapse-free at the end of the first 6-month treatment period were included in the relapse rate assessment at the end of the second 6-month treatment period. RESULTS: Reboxetine was associated with a markedly lower relapse rate than placebo (22% vs. 56%; p<.001) and a greater cumulative probability of a maintained response (p = .0001) during long-term treatment. Patients in remission (HAM-D total score < or =10) at the time of random assignment were less likely to relapse (16% reboxetine, 48% placebo; p<.001). The proportion of patients who were relapse-free and therefore remained in the study was significantly (p< or =.001) higher among those on reboxetine treatment than on placebo at the end of the first (61% vs. 40%) and second (88% vs. 59%) 6 months of treatment. Additional efficacy measures supported these findings. The incidence of adverse events with reboxetine was low and comparable with that for placebo. Discontinuation due to adverse events occurred infrequently. CONCLUSION: Reboxetine treatment over 1 year is more effective than placebo in the prevention of relapse in patients with recurrent depression. The low relapse rates at the end of the second 6 months of treatment further suggest that reboxetine effectively prevents recurrence of depressive symptoms following episode resolution. Reboxetine is well tolerated in long-term treatment of depression, a finding that bodes well for long-term patient compliance.

Adrenergic Uptake Inhibitors↗