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Background: The norepinephrine transporter in the brain has been targeted in the treatment of psychiatric disorders. Duloxetine is a serotonin and norepinephrine reuptake inhibitor that has been widely used for the treatment of depression. However, the relationship between dose and plasma concentration of duloxetine and norepinephrine transporter occupancy in the human brain has not been determined. In this study, we examined norepinephrine transporter occupancy by different doses of duloxetine., Methods: We calculated norepinephrine transporter occupancies from 2 positron emission tomography scans using (S,S)-[18F]FMeNER-D2 before and after a single oral dose of duloxetine (20 mg, n = 3; 40 mg, n = 3; 60 mg, n =2). Positron emission tomography scans were performed from 120 to 180 minutes after an i.v. bolus injection of (S,S)-[18F]FMeNER-D2. Venous blood samples were taken to measure the plasma concentration of duloxetine just before and after the second positron emission tomography scan., Results: Norepinephrine transporter occupancy by duloxetine was 29.7% at 20 mg, 30.5% at 40 mg, and 40.0% at 60 mg. The estimated dose of duloxetine inducing 50% norepinephrine transporter occupancy was 76.8 mg, and the estimated plasma drug concentration inducing 50% norepinephrine transporter occupancy was 58.0 ng/mL., Conclusions: Norepinephrine transporter occupancy by clinical doses of duloxetine was approximately 30% to 40% in human brain as estimated using positron emission tomography with (S,S)-[18F]FMeNER-D2., (© The Author 2017. Published by Oxford University Press on behalf of CINP.)

Objective: Aprepitant is a neurokinin 1 receptor antagonist approved for prevention of chemotherapy-induced and post-operative nausea and vomiting. Early studies demonstrated promising antidepressant activity as monotherapy, although this was unsupported by subsequent phase 3 trials. This phase 2 study evaluated whether aprepitant potentiated the antidepressant effects of paroxetine., Methods: Outpatients with major depressive disorder were randomized to aprepitant 200 mg + paroxetine 20 mg, paroxetine + placebo, or aprepitant + placebo for 6 weeks. The primary endpoint was change in HAMD-17 total score. Secondary/exploratory endpoints included changes in HAMA, CGI-S, CGI-I, and HAMD Item-1 scores at week 6., Results: A total of 79, 78, and 79 patients received aprepitant + paroxetine, paroxetine + placebo, and aprepitant + placebo, respectively. At week 6, mean changes in HAMD-17 were -11.0 (95% confidence interval [CI]: -12.7, -9.4), -11.7 (95% CI: -13.3, -10.0), and -9.5 (95% CI: -10.9, -8.1), respectively. Pairwise comparisons of HAMD-17 change with combination therapy versus paroxetine alone demonstrated no significant difference (p = 0.567). Changes in CGI-S, CGI-I, and HAMD Item-1 scores were also comparable, although there was a greater reduction in anxiety (HAMA) with paroxetine alone than aprepitant + paroxetine (p = 0.045). Adverse events were generally more common with the combination than either monotherapy., Conclusion: Concomitant use of aprepitant + paroxetine for 6 weeks did not provide greater antidepressant benefit compared with paroxetine + placebo in patients with major depression., (Copyright © 2014 John Wiley & Sons, Ltd.)

Antidepressants used for treatment of depression exert their efficacy by blocking reuptake at serotonin transporters (5-HTT) and/or norepinephrine transporters (NET). Recent studies suggest that serotonin and norepinephrine reuptake inhibitors that block both 5-HTT and NET have better tolerability than tricyclic antidepressants and may have higher efficacy compared to selective serotonin reuptake inhibitors. Previous positron emission tomography (PET) studies have reported >80% 5-HTT occupancy with clinical doses of antidepressants, but there has been no report of NET occupancy in patients treated with antidepressants. In the present study, we investigated both 5-HTT and NET occupancies by PET using radioligands [(11)C]DASB and (S,S)-[(18)F]FMeNER-D(2), in six patients, each with major depressive disorder (MDD), using various doses of milnacipran. Our data show that mean 5-HTT occupancy in the thalamus was 33.0% at 50 mg, 38.6% at 100 mg, 60.0% at 150 mg and 61.5% at 200 mg. Mean NET occupancy in the thalamus was 25.3% at 25 mg, 40.0% at 100 mg, 47.3% at 125 mg and 49.9% at 200 mg. Estimated ED(50) was 122.5 mg with the dose for 5-HTT and 149.9 mg for NET. Both 5-HTT and NET occupancies were observed in a dose-dependent manner. Both 5-HTT and NET occupancies were about 40% by milnacipran at 100 mg, the dose most commonly administered to MDD patients.

Background: A single 115-mg dose of fosaprepitant, the IV prodrug of the NK(1) receptor antagonist aprepitant, is bioequivalent to a 125-mg dose of oral aprepitant. Thus far, fosaprepitant/aprepitant has not shown a meaningful effect on QTc intervals; in this study, we sought to confirm these findings., Methods: This double-blind, active-controlled, randomized, three-treatment, three-period, crossover study in healthy young subjects evaluated the effect of a 200-mg dose of fosaprepitant on QTc prolongation. In each period, subjects received 400 mg moxifloxacin per os, 200 mg fosaprepitant IV, or placebo in randomized sequence. The effect of fosaprepitant on QTc interval was assessed by 12-lead electrocardiograms (ECGs). The baseline value for QTc interval for each subject during each period was defined as the average of five replicate baseline QTc intervals extracted from predose ECGs. ECGs were performed at predose, 2, 5, 10, 15, 20, 30, 45 min; and 1, 1.5, 2, 3, 4, 6, and 8 h postinfusion. Values for individual QTc change from baseline were evaluated in a repeated-measures mixed model appropriate for a crossover design. A two-sided 90% confidence interval (CI) for the true difference in QTc interval change from baseline at each timepoint was calculated for fosaprepitant versus placebo and for moxifloxacin versus placebo., Results: After fosaprepitant 200-mg administration, the mean (95% CI) QTc interval change from baseline at T(max) was -1.45 (-4.67 to 1.77) ms, and the placebo-corrected mean (90% CI) QTc interval change from baseline was -1.37 (-4.78 to 2.05) ms. Neither was statistically significant at alpha = 0.05. After 400 mg moxifloxacin administration, the mean (95% CI) QTc interval change from baseline at 2 h was 9.71 (6.49-12.93) ms, and the placebo-corrected mean (90% CI) QTc interval change from baseline at moxifloxacin T(max) was 10.50 (7.09-13.92) ms. Both were statistically significant at alpha = 0.05. The maximum aprepitant concentration after fosaprepitant 200 mg administration was 6300 ng/mL (approximately twofold, fourfold, and ninefold higher than that observed historically with fosaprepitant 115 mg [3095 ng/mL], aprepitant 125 mg [1600 ng/mL], and aprepitant 40 mg [675 ng/mL])., Conclusions: In subjects receiving fosaprepitant 200 mg, no clinically meaningful increases in QTc were seen at any timepoint, whereas after moxifloxacin 400 mg, increases were observed at the approximate T(max) of moxifloxacin and additional timepoints. The lack of QTc increase at this high dose of fosaprepitant and resulting aprepitant plasma exposures support the expectation that clinical doses of fosaprepitant or aprepitant will not be associated with significant QTc prolongation.

Objectives: The noradrenaline-selective antidepressant reboxetine in vitro is a weak inhibitor of both cytochrome P450 (CYP) 2D6 and CYP3A4. Thus, in this study the pharmacokinetics of reboxetine in relation to pharmacogenetics and the effects of reboxetine compared to paroxetine treatment on the CYP2D6 and CYP3A4 phenotype were analyzed in healthy control subjects., Methods: Healthy male volunteers were treated with either 6 mg reboxetine (n = 26) or 30 mg paroxetine (n = 25). On Days 10/11 of treatment, serum concentrations of the antidepressants were measured and pharmacokinetic parameters calculated. Volunteers were phenotyped at the end of treatment and after at least 3 weeks washout (true phenotype) using 30 mg dextromethorphan (DM) hydrobromide given orally and measuring DM and metabolites in serum 2 h after intake. CYP2D6 and CYP2C19 genotypes were determined in parallel., Results and Conclusion: Reboxetine serum concentrations showed no correlation with the CYP2D6 genotype and the CYP2D6 phenotype, whereas paroxetine concentrations showed some dependence on CYP2D6. In contrast to in vitro investigations, indicating a major role of CYP3A4 in reboxetine metabolism, reboxetine concentrations in serum showed no correlation with the respective DM metabolic ratios. There was also no correlation between paroxetine concentrations and the CYP3A4 phenotype data. The CYP2C19 genotype (only heterozygosity) had no influence on reboxetine and paroxetine pharmacokinetics. There were only minor changes in the DM metabolite pattern on treatment with reboxetine and no evidence of enzyme inhibition was obtained. In contrast and as expected, paroxetine strongly inhibited CYP2D6. Thus, reboxetine treatment has no effect on the CYP2D6 genotype and no clinically relevant drug interactions involving CYP2D6 are anticipated.

Brain extracellular fluid (ECF) concentration of YM992, a novel antidepressant, was determined using brain microdialysis to investigate the high partition of this drug to the brain after systemic administration to rats. Plasma, cerebrospinal fluid (CSF), ECF and brain concentrations were determined at the steady-state after intravenous infusion to rats. The concentration ratio of brain to plasma at the total concentration base was 71.3, while those of ECF to plasma and CSF to plasma at the free concentration base were comparable. The distribution volume in brain was 375 ml/g brain and in vitro binding of YM992 to rat brain was 98.1-98.5%, suggesting a high binding in the brain. The carotid artery injection study showed that the brain uptake index of YM992 was 141%, furthermore, the uptake clearance into brain after i.v. dosing to rats was 0.6 ml/min/g brain, indicating a high permeability at the blood-brain barrier (BBB). These findings suggest that the high partition of YM992 to rat brain is attributed to its high level of binding in the brain as well as its high permeability at the BBB., (Copyright 2002 John Wiley & Sons, Ltd.)

Reboxetine is a new norepinephrine reuptake inhibitor (NRI) drug recently introduced in the therapy for depressed patients. It is effective in the treatment of severe depression and safer to use than traditional tricyclic antidepressants. In this paper an original high-performance liquid chromatography (HPLC) method with ultraviolet detection for the determination of reboxetine in human plasma is described. It uses a C8 reversed-phase column and a mobile phase composed of acetonitrile and aqueous tetramethylammonium perchlorate. For the analysis of plasma samples containing very low levels of reboxetine, another HPLC method with fluorimetric detection was developed (limit of quantitation, LOQ=11 ng ml(-1); limit of detection, LOD=4 ng ml(-1)). The fluorimetric method is based on precolumn derivatisation of reboxetine with 9-fluorenylmethyl chloroformate. An accurate sample pretreatment of human plasma samples has been implemented by means of solid-phase extraction (SPE) on Oasis HLB (hydrophilic-lipophilic balance) cartridges with very high extraction yields (>95%). Both methods were applied to the analysis of plasma samples from depressed patients undergoing therapy with reboxetine and gave satisfactory results in terms of precision (RSD<4.5%) and accuracy (mean recovery>94%).

Background: Moclobemide, an antidepressant with selective monoamine oxidase-A inhibitory action, is known to be metabolized by CYP2C19 and is also reported to be an inhibitor of CYP2C19, CYP2D6, and CYP1A2. To confirm the involvement of CYP2C19, we performed a pharmacokinetic interaction study., Methods: The effect of omeprazole on the pharmacokinetics of moclobemide was studied in 16 healthy volunteers. The volunteer group comprised 8 extensive metabolizers and 8 poor metabolizers of CYP2C19, which was confirmed by genotyping. Subjects were randomly allocated into two sequence groups, and a single-blind, placebo-controlled, two-period crossover study was performed. In study I, a placebo was orally administered for 7 days. On the eighth morning, 300 mg of moclobemide and 40 mg of placebo were coadministered with 200 mL of water, and a pharmacokinetic study was performed. During study II, 40 mg of omeprazole was given each morning instead of placebo, and pharmacokinetic studies were performed on the first and eighth day with 300 mg of moclobemide coadministration., Results: The inhibition of moclobemide metabolism was significant in extensive metabolizers even after a single dose of omeprazole. After daily administration of omeprazole for 1 week, the pharmacokinetic parameters of moclobemide and its metabolites in extensive metabolizers changed to values similar to those in poor metabolizers. In poor metabolizers, no remarkable changes in the pharmacokinetic parameters were observed., Conclusion: Our results show that CYP2C19 is an important enzyme in the elimination of moclobemide and that it is extensively inhibited by omeprazole in extensive metabolizers, but not in poor metabolizers.

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.

Objective: To review the pharmacology, pharmacokinetics, efficacy, and tolerability of reboxetine in the treatment of major depressive illness., Data Sources: A MEDLINE search restricted to English-language literature was conducted (1966 to July 1999). Abstracts and posters presented at meetings were also reviewed. DATA EXTRACTION/STUDY SELECTION: Studies currently available were conducted in Europe. Data from clinical trials were reviewed to gather information specific to efficacy analysis, pharmacokinetic parameters, tolerability profiles, and drug-drug interactions. Information on reboxetine was compared with other antidepressant therapies when appropriate data were available., Data Synthesis: Reboxetine is a selective norepinephrine reuptake inhibitor shown to be an effective agent in the treatment of major depressive illness. In clinical trials, reboxetine was effective in decreasing mean total scores of the Hamilton Rating Scale for Depression in adult populations. Improvements were similar between reboxetine and desipramine and imipramine, as well as fluoxetine. Reboxetine is relatively well tolerated, with insomnia, sweating, constipation, and dry mouth being commonly reported adverse events. Hypotension and urinary hesitancy occur at lower rates than with the tricyclics, and compared with fluoxetine, reboxetine is associated with lower rates of nausea, somnolence, and diarrhea. Dosage adjustments may be appropriate in elderly patients and those with renal and hepatic impairment., Conclusions: Reboxetine has received two letters of approval from the Food and Drug Administration for the treatment of major depression in adults. Upon completion of an additional US clinical study, reboxetine is likely to become a first-line agent in the management of depressive illness and a promising alternative for patients who have failed treatment with or do not tolerate serotonergic antidepressants.

The pharmacokinetic characteristics of reboxetine, a unique selective noradrenaline reuptake inhibitor (selective NRI) for the treatment of depression, were studied in 12 healthy, elderly volunteers (mean age 81 years +/- 9 years). All subjects received a single 4-mg dose of reboxetine, and plasma reboxetine concentrations were measured by HPLC. Reboxetine was well tolerated by all subjects. Exposure to reboxetine was higher in this group of very elderly subjects, compared with data obtained in a similar study of young, healthy volunteers. Cmax in the elderly was 271 +/- 86 ng/ml, compared with 111 +/- 28 ng/ml in the young subjects after a single 4-mg dose, although in both groups Cmax was observed after 2 h. The AUC infinity was nearly four times that in the younger subjects (8345 +/- 3107 ng.h/ml vs. 2106 +/- 881 ng.h/ml) and the t1/2 was twice as long (24 +/- 6 h vs. 12 +/- 3 h). Renal clearance was also reduced. Reboxetine 8-10 mg/day has been effective and well tolerated in clinical trials in non-elderly depressed patients. The increased exposure to reboxetine observed in our very elderly subjects supports a reduction of the starting dose to 4 mg/day (in two divided doses) in the elderly.

The selective serotonin reuptake inhibitors (SSRIs) have obtained global attention but have not demonstrated superior efficacy in major depression compared with older tricyclic antidepressants. From a pharmacological viewpoint the noradrenergic system in the brain appears to have a central role in neurotransmitter organization. The importance of noradrenaline in depression is supported by its association with clinical parameters such as vigilance and drive. Reboxetine is a selective noradrenaline reuptake inhibitor--the first in its class to be marketed. In both preclinical and clinical studies reboxetine has been found to be an effective and safe antidepressant. Furthermore, reboxetine restores a patients' social functioning, producing a better quality of remission than fluoxetine.

Reboxetine is a new antidepressant acting by selective inhibition of noradrenaline reuptake (NARI) at the synaptic cleft. The efficacy of reboxetine is similar to other antidepressants such as tricyclic and Selective Serotonin reuptake inhibitors once (SSRI). A faster onset of action (in a mean of 10 days) is suggested by preliminary studies. Reboxetine seems also to improve social adjustment of the treated depressed patients. Due to its selectivity, reboxetine presents a favourable safety profile. Treatment of depression will certainly benefit from this new compound. However, some issues need to be clarified such as the use of reboxetine in combination with other antidepressants.

In vitro studies were conducted to identify the hepatic cytochrome P-450 (CYP) enzymes responsible for the oxidative metabolism of the individual enantiomers of reboxetine. In human liver microsomes, each reboxetine enantiomer was metabolized to one primary metabolite, O-desethylreboxetine, and three minor metabolites, two arising via oxidation of the ethoxy aromatic ring and a third yet unidentified metabolite. Over a concentration range of 2 to 200 microM, the rate O-desethylreboxetine formation for either enantiomer conformed to monophasic Michaelis-Menten kinetics. Evidence for a principal role of CYP3A in the formation of O-desethylreboxetine for (S, S)-reboxetine and (R,R)-reboxetine was based on the results from the following studies: 1) inhibition of CYP3A activity by ketoconazole markedly decreased the formation of O-desethylreboxetine, whereas inhibitors selective for other CYP enzymes did not inhibit reboxetine metabolism, 2) formation of O-desethylreboxetine correlated (r(2) = 0.99; p <.001) with CYP3A-selective testosterone 6-beta-hydroxylase activity across a population of human livers (n = 14). Consistent with inhibition and correlation data, O-desethylreboxetine formation was only detectable in incubations using microsomes prepared from a Baculovirus-insect cell line expressing CYP3A4. Furthermore, the apparent K(M) for the O-desethylation of reboxetine in cDNA CYP3A4 microsomes was similar to the affinity constants determined in human liver microsomes. In addition, (S,S)-reboxetine and (R,R)-reboxetine were found to be competitive inhibitors of CYP2D6 and CYP3A4 (K(i) = 2.5 and 11 microM, respectively). Based on the results of the study, it is concluded that the metabolism of both reboxetine enantiomers in humans is principally mediated via CYP3A.

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.

Reboxetine is a racemic mixture of FCE 22071 and FCE 21684 enantiomers. The pharmacokinetics of the enantiomers of reboxetine were observed to be linear in male healthy subjects (n = 6) after the administration of 1.5, 3, 4.5 mg dose of reboxetine as solutions. Kinetic analysis was based on chiral HPLC assay of the enantiomers in plasma collected up to 72 h after each administration. C(max) and AUC were more than double for FCE 22071 (C(max): 38.3+/-13.5, 76. 6+/-26.3, 99.8+/-24.1 ng/mL and AUC(infinity): 605.8+/-233.2, 1288. 3+/-796.4, 1780.7+/-669.3 ng. h/mL for 1.5, 3, 4.5 mg, respectively) than for FCE 21684 (C(max): 15.2+/-5.3, 34.6+/-14.0, 43.1+/-12.3 ng/mL and AUC(infinity): 247.0+/-103.9, 529.1+/-278.4, 773.0+/-355.3 ng. h/mL), whatever the administered dose. The half-lives of the enantiomers were similar (FCE 22071: 13.1, 11.0, 12.6 h and FCE 21684: 12.8, 11.2, 12.2 h after 1.5, 3, 4.5 mg, respectively) and not substantially affected by the dose level., (Copyright 1999 John Wiley & Sons, Ltd.)

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.

Indeloxazine hydrochloride (IDX), a cerebral activator, has a bitter astringent taste. To prepare powders of IDX without this bitter taste, microparticles (median diameter, 130 microns) of IDX were coated with a mixture comprising hydrogenated oil and surfactants in a fluidized bed using the side-spray method. Drug release from the resulting coated particles was significantly delayed. Dissolution rate was remarkably enhanced, however, by heat-treating the coated particles at a temperature above the melting point of the surfactant in the coated layer. The results of differential scanning calorimetry measurements show that part of the surfactant in the coated layer exists separately. Further, surface changes in the coated layer before and after heat treatment showed that this enhancement of dissolution rate was due to rediffusion of the surfactant in the coated layer followed by melting of the surfactant. This effect allows the design of powders of IDX which release the drug quickly and with bioequivalence to the commercial IDX 20 mg tablets while sufficiently suppressing the bitter taste.

The pharmacokinetics and metabolism of reboxetine, a selective noradrenaline reuptake inhibitor, in humans and animal models are reviewed here. Reboxetine has potent antidepressant activity, low affinity for alpha-adrenergic and muscarinic receptors and low toxicity in animals. It is a mixture of (R,R) and (S,S) enantiomer, the latter being more potent but no qualitative differences in pharmacodynamic properties are observed between the two. Humans rapidly absorb reboxetine (tmax about 2 h) with a terminal half-life of elimination (t1/2) of 13 h, allowing twice-daily administration. Animal models also rapidly absorb reboxetine (tmax 0.5-2 h) but t1/2 was 1-2 h. Food does not affect bioavailability. There were no major inter-species differences in the metabolic profile of reboxetine. Elimination is principally renal in humans and monkeys. Reboxetine has linear pharmacokinetics in young, healthy males for single doses of 1-5 mg and in elderly, female depressed patients (up to 4 mg b.i.d.). Multiple dosing, gender or liver insufficiency had no significant effects on the pharmacokinetics. Elderly (particularly frail elderly) patients and patients with severe renal impairment may need dose reduction. Reboxetine shows no clinically relevant interaction with lorazepam and has no inhibitory effects on the major enzymes involved in drug metabolism. It may be possible to use reboxetine in combination with monoamine oxidase inhibitors as it has no inhibitory effect on this enzyme; in addition, it may protect patients against tyramine-induced reactions. In conclusion, reboxetine seems to be an antidepressant with negligible interference with the pharmacokinetics of other drugs thus fewer drug-drug interactions are expected.

Reboxetine, (RS)-2-[(RS)-alpha-(2-ethoxyphenoxy)benzyl]morpholine methanesulphonate, is a racemic compound and consists of a mixture of the (R,R)- and (S,S)-enantiomers. The pharmacokinetics of reboxetine enantiomers were determined in a crossover study in three male beagle dogs. Each animal received the following oral treatments, separated by 1-week washout period: 10 mg/kg reboxetine, 5 mg/kg (R,R)- and 5 mg/kg (S,S)-. Plasma and urinary levels of the reboxetine enantiomers were monitored up to 48 h post-dosing using an enantiospecific HPLC method with fluorimetric detection (LOQ: 1.1 ng/ml in plasma and 5 ng/ml in urine for each enantiomer). After reboxetine administration mean tmax was about 1 h for both enantiomers. Cmax and AUC were about 1.5 times higher for the (R,R)- than for the (S,S)-enantiomer, mean values +/- SD being 704 +/- 330 and 427 +/- 175 ng/ml for Cmax and 2,876 +/- 1,354 and 1,998 +/- 848 ng.h/ml for AUC, respectively. No differences between the (R,R)- and (S,S)-enantiomers were observed in t1/2 (3.9 h). Total recovery of the two enantiomers in urine was similar, the Ae (0-48 h) being 1.3 +/- 0.7 and 1.1 +/- 0.7% of the enantiomer dose for the (R,R)- and the (S,S)-enantiomers, respectively. No marked differences in the main plasma pharmacokinetic parameters were found for either enantiomer on administration of the single enantiomers or reboxetine. No chiral inversion was observed after administration of the separate enantiomers, as already observed in humans.

The pharmacokinetics of reboxetine have been investigated in 12 healthy male volunteers after a single 2 mg dose of reboxetine and at steady state, following the last administration of a multiple-dose regimen (2mg twice a day for 5 1/2 d). Reboxetine was analysed in plasma and urine samples collected up to 72 h post-dosing using an HPLC method with UV detection. The urinary excretion rate of 6-beta-hydroxycortisol, used as a marker for cytochrome P450IIIA activity, was also tested, and any possible alteration was correlated to reboxetine plasma levels. The dosing regimen was well tolerated by all subjects. Reboxetine pharmacokinetic parameters, calculated after the single dose using non-compartmental analysis, were in good agreement with those obtained in previous studies. Following the multiple-dosing regimen, no significant deviations from expectation based on linear superposition was observed. The accumulation ratio, based on repeated-dose/single-dose ratios of Cmax, AUC(0-12 h), and C(12 h) was approximately two. A slight rise was recorded for the average excretion rate of 6-beta-hydroxycortisol over 48 h by the end of treatment; however, the difference was not statistically significant and the mean excretion rates were within the normal reference range. Thus a significant induction of P450IIIA was not indicated.

The pharmacokinetics of reboxetine, a new antidepressant agent, were found to be close to linear in a crossover study comparing administration of single 2, 3, 4, and 5 mg capsule doses in 15 healthy male volunteers, and in the same study the capsules were bioequivalent to the proposed therapeutic tablet formulation (4 mg). Kinetic analysis was based on HPLC assay of reboxetine in plasma and urine collected up to 72 h after each administration. Plasma levels indicated a rapid absorption (tmax approximately equal to 2 h) and an elimination half-life of about 13 h. Clearance and volume of distribution were modest (ratios to bioavailability: CL/F approximately equal to 29 mL min-1; Vz/F approximately equal to 32 L); urinary excretion was approximately 9% of dose, corresponding to a renal clearance of only 3 mL min-1 (a value consistent with the rate of glomerular filtration of unbound drug). In vitro, binding to plasma proteins, estimated from radioactivity levels following dialysis of 14C-labelled reboxetine, appeared to be dominated by alpha 1-acid glycoprotein without marked saturation up to plasma concentrations of over 500 ng mL-1 (2.8-3.1% unbound with human plasma from three additional volunteers; 1.8-2.0% for 2 gL-1 orosomucoid alpha 1-acid glycoprotein, and 46.4-47.4% for 40 g L-1 albumin), whilst the mean Cmax in the current study was much lower (164 ng mL-1 after a 5mg dose).

Reboxetine, (RS)-2-[(RS)-alpha-(2-ethoxyphenoxy)benzyl]morpholine methanesulphonate, is a racemic compound and consists of a mixture of the (R,R)- and (S,S)-enantiomers. In this study, brain and plasma levels of both enantiomers were determined in mice and rats after oral administration of reboxetine at doses (1.1 mg/kg, mouse; 20 mg/kg, rat) twice the respective ED50 values in the antireserpine test. Plasma and brain concentrations of each enantiomer were measured up to 6 h postdosing using an HPLC method with fluorimetric detection after derivatization with a chiral agent (FLEC). In mice and rats, brain and plasma levels of the (R,R)-enantiomer were always higher than those of the (S,S)-enantiomer. After normalization for dose, the mean AUC0-tz values of both the (R,R)- and (S,S)-enantiomers in mouse brain were about 23 and 32 times higher than in rat brain, respectively. In plasma, the corrected mean AUC0-tz values were about 5 (R,R) and 10 (S,S) times higher in mice than in rats. These results provide evidence for the higher bioavailability and/or lower clearance of both enantiomers in mice than in rats, and for a higher penetration of both enantiomers into mouse brain compared to rat brain.

A case of severe poisoning in a 2 year-old child who ingested 150 mg of oxaflozane, a non-tricyclic antidepressant, is reported. After loss of consciousness, opisthotonos and coma, recovery was obtained with conservative treatment. Atropine-like symptoms were noted. The maximal plasma concentration of oxaflozane was 63 ng/mL. The elimination half-life for N-dealkyloxaflozane was 4.8 h.

The purpose of this study was to compare the disposition and the metabolic pattern of Reboxetine in several species, including man. [14C]-Reboxetine was given orally to the rat, the dog, the monkey (5 mg/kg) and man (2 and 4 mg/kg). Radioactivity was eliminated both by the renal and faecal route in the rat and the dog, mainly in urine in the monkey and man. Reboxetine was extensively metabolized. A number of urinary metabolites were quantified by radio-HPLC and tentatively identified by comparison with the retention times of reference compounds. Suggested routes of metabolic transformation are: 2-O-dealkylation; hydroxylation of the ethoxyphenoxy ring; oxidation of the morpholine ring; morpholine ring-opening; and combinations of these. Metabolites were partially or completely conjugated with glucuronic acid and/or sulphuric acid.

The pharmacokinetics of befol at different routes of administration to animals and humans was studied. The therapeutic level of the drug concentration was established.

The structure of the urinary metabolites formed after moclobemide administration in human was elucidated, and the pattern compared with that in the plasma. The metabolic pathways of moclobemide were also compared with those of structurally related substances. After oral moclobemide administration, on average 95% of the dose was recovered in the urine within 4 days, with a mean of 92% being excreted during the first 12 h. The drug is extensively metabolized: less than 1% of the dose was excreted unchanged. A total of 19 metabolites, accounting together for about 64% of the dose, was isolated and all metabolites accounting for more than 1% of the dose were identified. Consistent with other morpholine-containing compounds, metabolic pathways of moclobemide include mainly oxidative attack on the morpholine moiety, leading to a multitude of oxidation products. Four primary metabolic reactions were identified: morpholine N-oxidation, aromatic hydroxylation, morpholine C-oxidation and deamination. The major metabolites in urine are 4 carboxylic acids (M7A and M7B, M8, M9) that account for 49% of the dose. Only 2 metabolites (M3, M10) were found to be hydroxylated on the aromatic nucleus. They were excreted completely as conjugates of glucuronic and/or sulfuric acid. Conjugation in general, however, seems to be of minor importance in the overall biotransformation of the drug. The metabolite pattern in plasma was found to be qualitatively but not quantitatively similar to that observed in urine. Almost all of the main urinary metabolites were found in plasma as well. The unchanged parent compound and 2 primary oxidation products of the morpholine ring (M1, M15), which were present in urine only in trace amounts, could easily be detected in plasma.