Absence of discontinuation symptoms with agomelatine and occurrence of discontinuation symptoms with paroxetine: a randomized, double-blind, placebo-controlled discontinuation study

Cellular and molecular mechanisms in the long-term action of antidepressants

The hypotheses on the pathophysiology of depression/mood disorders and on antidepressant mechanisms have greatly changed in recent years. The classical monoamine hypothesis was revealed to be simplistic, in that it could not explain the temporal delay in the therapeutic action of antidepressants. Converging lines of evidence have shown that adaptive changes in the several mechanisms of neuroplasticity are likely to be the cellular and molecular correlates of therapeutic effect. In this article, several mechanisms of neuroplasticity are analyzed in relation to the mechanism of antidepressants, ranging from changes in gene expression (including neurotrophic mechanisms), to synaptic transmission and plasticity, and neurogenesis. We propose that the current version of the hypothesis of antidepressant mechanism simply be called the "hypothesis of neuroplasticity". In the final section, we also briefly review the main current novel strategies in the pharmacology of depression and the new putative targets for antidepressants, with particular emphasis on nonmonoaminergic mechanisms.

Bipolar disorder: candidate drug targets

Current pharmacotherapy for bipolar disorder is generally unsatisfactory for a large number of patients. Even with adequate modern bipolar pharmacological therapies, many afflicted individuals continue to have persistent mood episode relapses, residual symptoms, functional impairment, and psychosocial disability. Creating novel therapeutics for bipolar disorder is urgently needed. Promising drug targets and compounds for bipolar disorder worthy of further study include both systems and intracellular pathways and targets. Specifically, the purinergic system, the dynorphin opioid neuropeptide system, the cholinergic system (muscarinic and nicotinic systems), the melatonin and serotonin [5-hydroxytryptamine receptor 2C] system, the glutamatergic system, and the hypothalamic-pituitary adrenal axis have all been implicated. Intracellular pathways and targets worthy of further study include glycogen synthase kinase-3 protein, protein kinase C, and the arachidonic acid cascade.

Agomelatine treatment of major depressive disorder

OBJECTIVE

To review the efficacy, safety, pharmacologic, and pharmacokinetic data of agomelatine to better understand its potential role in the treatment of patients with major depressive disorder.

DATA SOURCES

A MEDLINE search (1966-October 2008) was conducted using the following terms: agomelatine, antidepressant, S20098, melatonin, serotonin, 5-HT(2C), MT, efficacy, safety, adverse effect, pharmacology, pharmacokinetic, receptor binding, depression, major depressive disorder, and mood disorder.

STUDY SELECTION AND DATA EXTRACTION

All articles in English identified from the data sources were evaluated. Randomized, controlled trials involving humans were prioritized in the review. The references of published articles identified in the initial search process were also examined for any additional studies appropriate for the review.

DATA SYNTHESIS

Agomelatine, a potent agonist at type 1 and 2 melatonin receptors, selectively inhibits serotonin. It is extensively metabolized via cytochrome P450 isoenyzmes 1A1, 1A2, and 2C9 to metabolites with less activity than the parent drug. Five randomized controlled studies were identified that examined the efficacy and safety of agomelatine in major depressive disorder. In general, agomelatine was found to produce significant improvements in depressive symptoms compared with placebo on many, but not all, rating scales. Three of the trials had active comparator arms (ie, venlafaxine, paroxetine). In these 3 investigations, agomelatine produced effects on depressive symptoms similar to those of the comparator drugs. A small number of studies have demonstrated sleep benefits with the use of agomelatine in depressed patients. Positive findings also exist for the use of agomelatine in seasonal affective disorder and bipolar depression. The most common adverse effects reported with agomelatine use were headache, nasopharyngitis, and gastrointestinal complaints. The magnitude of agomelatine-related adverse effects appears to be at least similar to some currently marketed antidepressants.

CONCLUSIONS

Overall, agomelatine is a promising and well-tolerated medication for the treatment of major depressive disorder. More large-scale controlled trials are needed to gain a better understanding of the relative efficacy and safety of agomelatine.

Efficacy of agomelatine in generalized anxiety disorder: a randomized, double-blind, placebo-controlled study

BACKGROUND

Agomelatine is a novel agent that acts on melatonergic (MT(1), MT(2)) receptors and serotonergic (5-HT(2C)) receptors. Preclinical data and data from clinical trials in major depression suggest that agomelatine may have anxiolytic properties. A randomized, double-blind, placebo-controlled trial was designed to assess the efficacy of agomelatine in generalized anxiety disorder (GAD).

METHODS

One hundred twenty-one patients with Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition GAD and no comorbid disorders were randomized to agomelatine (25-50 mg/d) or placebo for 12 weeks. The primary outcome measure was the Hamilton Anxiety Rating Scale, whereas secondary outcome measures included the Clinical Global Impression scales, the Leeds Sleep Evaluation Questionnaire, and the Sheehan Disability Scale. Safety measures included assessment of spontaneously reported adverse events, laboratory monitoring, and the Discontinuation Emergent Signs and Symptoms Scale to evaluate discontinuation symptoms.

RESULTS

Analysis of covariance of change in the last Hamilton Anxiety Rating Scale total score from baseline demonstrated significant superiority of agomelatine 25 to 50 mg as compared with placebo (E [SE] = -3.28 [1.58]; 95% confidence interval = -6.41 to -0.15; P = 0.040). Data on secondary outcome measures, including clinical response, symptoms of insomnia, and improvement in associated disability, were consistent with the efficacy of agomelatine. Safety analysis indicated that agomelatine was tolerated as well as placebo and was devoid of discontinuation emergent symptoms.

CONCLUSIONS

This study suggests that agomelatine is effective in the treatment of GAD and is well tolerated. Additional trials, using an active comparator and extending over a longer period, are needed to delineate the place of agomelatine in the contemporary pharmacotherapy for anxiety disorders.

Innovation translates into antidepressant effectiveness

Unipolar depression is a major cause of disability in developed societies. There is significant unmet need because existing treatments are neither as effective nor as free of adverse effects as we would hope. Agomelatine is a new antidepressant with a novel profile of pharmacological action. Its efficacy in major depression has been reported in short-term placebo-controlled trials and in direct head-to-head comparison with existing products. The pooling of data from the agomelatine short-term studies allows analysis of sub-groups within the study populations. There is a trend for a larger effect size to be seen with more severely ill patients as a consequence of placebo responses falling. Efficacy is also reported in the maintenance of effect seen after clinical response in a recently completed relapse prevention study, analysed initially after 6 months. What is unusual, certainly compared with the selective serotonin reuptake inhibitors (SSRIs) and venlafaxine, is the clear absence of an excess of early relapses soon after agomelatine withdrawal. This parallels the absence of an immediate withdrawal effect seen in the pattern of subjective symptoms in another study. It underlines the distinct and novel pharmacological properties of the product, and has evident clinical advantages for the patient. Agomelatine is well tolerated in other respects; only occasional dizziness emerges at significant rates higher than with placebo in the controlled data.

Efficacy, safety, and tolerability of desvenlafaxine 50 mg/day and 100 mg/day in outpatients with major depressive disorder

OBJECTIVE

To assess the efficacy, safety, and tolerability of 50- and 100-mg/day doses of desvenlafaxine (administered as desvenlafaxine succinate), a serotonin-norepinephrine reuptake inhibitor, for the treatment of major depressive disorder (MDD).

RESEARCH DESIGN AND METHODS

Patients with Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) MDD and 17-item Hamilton Rating Scale for Depression (HAM-D(17)) scores > or =20 were randomly assigned to double-blind placebo or desvenlafaxine treatment (fixed dose of 50 mg/day or 100 mg/day) for 8 weeks. The primary efficacy measure was the HAM-D(17). Changes from baseline in HAM-D(17) scores were analyzed using analysis of covariance. The final on-therapy evaluation was the primary endpoint for efficacy analyses, using last-observation-carried-forward data. MAIN OUTCOMES MEASURES AND RESULTS: The intent-to-treat population included 447 patients. Desvenlafaxine 50 mg was associated with a significantly greater adjusted mean change from baseline on the HAM-D(17) (-11.5) compared with placebo (-9.5, p=0.018); the 100-mg dose group (-11.0) did not achieve statistical significance (p=0.065). The 100-mg dose group experienced significant improvements compared with placebo on several secondary efficacy measures, including the 6-item Hamilton Depression Rating Scale (p=0.038) and the Visual Analog Scale-Pain Intensity total score (p=0.041). Both desvenlafaxine doses were generally well-tolerated. The most common adverse events (incidence > or =10% in either desvenlafaxine group and twice the rate of placebo) were dry mouth, constipation, insomnia, decreased appetite, hyperhidrosis, and dizziness.

CONCLUSIONS

These results demonstrate efficacy, safety, and tolerability of desvenlafaxine 50 mg/day for treating MDD. The significant findings on secondary measures support the efficacy of desvenlafaxine 100 mg, as seen in other trials. Conclusions may be limited by the exclusion of MDD patients with comorbid conditions and the short-term desvenlafaxine treatment duration.

Therapeutic potential of melatonin agonists

Melatonin, a hormone secreted by the pineal gland, has been successfully employed to improve sleep in both normal patients and insomniacs, and for the treatment of circadian rhythm sleep disorders. Melatonergic MT₁ and MT₂ receptors exist in high concentrations in the suprachiasmatic nucleus of the hypothalamus and have been shown to be instrumental for the sleep-promoting and circadian rhythm-regulating effects of melatonin. A lack of consistency among reports on the therapeutic efficacy of melatonin has been attributed to differences in melatonin's bioavailability and the short half-life of the hormone. In view of the need for longer acting melatonergic agonists that improve sleep efficiency without causing drug abuse or dependency, ramelteon (Rozerem™, Takeda) was developed. Ramelteon, which acts via MT₁/MT₂ melatonergic agonism, has been found clinically effective for improving total sleep time and sleep efficiency in insomniacs. Agomelatine (Valdoxan™, Servier) is another MT₁/MT₂ melatonergic agonist that also displays antagonist activity at 5-HT_2C serotonin receptors. Agomelatine has been found effective in treating depression and sleep disorders in patients with major depressive disorder. A slow-release preparation of melatonin (Circadin™, Neurim) has been shown to be effective in treating sleep disorders in the elderly population.

A review of the efficacy and tolerability of agomelatine in the treatment of major depression

Agomelatine is a novel agent that is under late-stage development as a potential antidepressant. Compared with available antidepressant agents, the drug may have a distinct mechanism of action, with significant interactions with melatonin receptors, in addition to serotonergic brain systems. Agomelatine has been shown to be active in preclinical models indicative of antidepressant activity and the results of a large-scale clinical trial programme, conducted in major depressive disorder, indicate both antidepressant activity and a favourable tolerability profile. As agomelatine may have a pharmacological profile and mechanism of action distinct from available agents, it may come to represent a valuable additional treatment option in those patients who do not respond fully or who prove unable to tolerate the side effects of existing antidepressants.

Limitations of current medical treatments for depression: disturbed circadian rhythms as a possible therapeutic target

The proportion of diagnosed depressives prescribed antidepressants has increased markedly over the last 20 years, mainly following the introduction of the selective serotonin reuptake inhibitors. However, currently available antidepressants have notable limitations, relating to their only moderate efficacy relative to placebo, relatively slow onset of action, possible withdrawal symptoms, and problems of compliance. Sleep disturbances are often used to identify newly presenting depressive patients, and may be part of a more general alteration of bodily rhythms. There are links between pharmacological treatments and circadian rhythms in depression, which might represent another, new option for the development of a therapeutic approach to depression treatment. Many antidepressants affect sleep, some are sedative, and others have been used specifically in severely insomniac depressives. Disturbances in circadian rhythms may be an integral part of depressive mechanisms, and normalising them via an innovative mechanism of antidepressant action may be a fruitful avenue in the search for improved antidepressant agents.

Non-REM sleep instability in patients with major depressive disorder: Subjective improvement and improvement of non-REM sleep instability with treatment (Agomelatine)

OBJECTIVE

To assess the importance of non-rapid eye movement (NREM) sleep disturbance in major depressive disorder (MDD) patients using cyclic alternating pattern (CAP) analysis, and to determine the usefulness of CAP analysis in evaluating treatment effect.

METHODS

Baseline sleep-staging data and CAP analysis of NREM sleep was compared in 15 MDD patients (Hamilton depression scale score>20) and normal controls. Longitudinal evaluation of sleep changes using similar analysis during a treatment trial was also performed.

ANALYSIS

A single-blinded researcher scored and analyzed the sleep of MDD and age-matched normal controls at baseline and during a treatment trial using the international scoring system as well as CAP analysis.

RESULTS

MDD patients had evidence of disturbed sleep with both analyses, but CAP analysis revealed more important changes in NREM sleep of MDD patients at baseline than did conventional sleep staging. There was a significant decrease in CAP rate, time, and cycle and disturbances of phase A subtype of CAP. NREM abnormalities, observed by CAP analysis, during the treatment trial paralleled subjective responses. Analysis of subtype A phase of CAP demonstrated better sleep improvement.

CONCLUSION

CAP analysis demonstrated the presence of more important NREM sleep disturbances in MDD patients than did conventional sleep staging, suggesting the involvement of slow wave sleep (SWS) in the sleep impairment of MDD patients. Improvement of NREM sleep paralleled subjective mood improvement and preceded REM sleep improvement. CAP analysis allowed objective investigation of the effect of treatment on sleep disturbances.

Efficacy of agomelatine, a MT1/MT2 receptor agonist with 5-HT2C antagonistic properties, in major depressive disorder

Current antidepressants used in major depressive disorder (MDD) are still not efficacious enough for many patients due to high levels of treatment resistance and bothersome side-effects. Using a novel blinding method (interactive voice response system), this flexible-dosing study examined the effects of therapeutic doses of agomelatine, a new approach to depressive therapy offering potent melatonergic MT1/MT2 receptor agonism with 5-HT2C receptor antagonist properties, in patients with moderate-to-severe MDD. This 6-wk, double-blind, parallel-group study randomized 238 patients to 25 mg/d agomelatine (with dose adjustment at 2 wk to 50 mg/d in patients with insufficient improvement) or placebo. Depression severity was assessed using the Hamilton Depression Rating Scale (HAMD) and the Clinical Global Impression (CGI) scale. Agomelatine was significantly more efficacious than placebo, with an agomelatine-placebo difference of 3.44 (p<0.001) using the HAMD final total score. Compared with placebo, agomelatine also had a significant positive impact on CGI - Improvement (treatment difference=0.45) and CGI - Severity (treatment difference=0.50) (both p=0.006), response rate (54.3% vs. 35.5% with placebo, p<0.05) and time to first response (p=0.008). Similar results were seen in patients with the most severe MDD. Depressed mood and sleep items of the HAMD were also significantly improved with agomelatine, which was well tolerated with a safety profile similar to placebo at both doses. This study confirms that agomelatine is effective in treating major depression, including the most severely depressed patients, with a good safety and tolerability profile, therefore providing physicians with an effective pharmacological approach to antidepressant therapy.

Evidence of agomelatine's antidepressant efficacy: the key points

Depressive disorders are of the highest socioeconomic and health-economic importance, as they are the psychiatric disorders that most frequently cause psychosocial disability. Despite the progress that has been made, currently available pharmacotherapies for depression still have a limited antidepressant efficacy with a delayed onset of several weeks, and still cause side effects; these unmet needs represent important reasons to continue to search for novel treatment options. A disorganization of circadian rhythms has been suggested to play an important role in the pathophysiology of major depression, and complaints regarding disturbed sleep are frequent in depressed patients. As endogenous melatonin secretion underlies the regulation of circadian rhythms, compounds with activity at melatonergic receptors have been proposed as potential novel therapeutics. Agomelatine (S-20098), a compound with agonistic properties at MT1 and MT2 receptors and antagonistic properties at the 5-HT2C receptor, has been shown preclinically to exhibit robust antidepressant effects in several experimental paradigms. Clinical trials, including phase III studies, have now demonstrated the superior efficacy of agomelatine in comparison with placebo, and a similar efficacy in comparison with active comparators, for the treatment of major depression. Agomelatine was even effective in severely depressed patients. In all studies published so far, agomelatine was found to be safe and its overall tolerability profile was superior to that of selective serotonin reuptake inhibitors and selective serotonin and noradrenaline reuptake inhibitors.

Agomelatine adjunctive therapy for acute bipolar depression: preliminary open data

OBJECTIVES

Agomelatine has been shown to be safe and efficient in the treatment of major depressive disorder at 25 mg daily. The aim of this study was to gather preliminary data regarding the antidepressant efficacy of agomelatine in patients with bipolar I disorder experiencing a major depressive episode.

METHODS

Bipolar I patients on lithium (n = 14) or valpromide (n = 7), with a Hamilton Rating Scale for Depression (HAM-D-17) total score > or = 18, were given adjunctive open-label agomelatine at 25 mg/day for a minimum of 6 weeks followed by an optional extension of up to an additional 46 weeks.

RESULTS

Using intent-to-treat data, 81% of patients met criteria for marked improvement (>50% improvement from baseline in HAM-D score) at study endpoint. Patients were severely depressed at study entry (HAM-D of 25.2) and 47.6% responded as early as at one week of treatment. Nineteen patients entered the optional extension period for a mean of 211 days (range 6-325 days). Eleven patients completed the one-year extension on agomelatine. There were no dropouts due to adverse events during the acute phase of treatment (6 weeks). Six patients experienced serious adverse events during the one-year period. Three lithium-treated patients experienced manic or hypomanic episodes during the optional extension period, one of which was treatment-related.

CONCLUSIONS

These results indicate the effectiveness of agomelatine 25 mg in the treatment of depressed bipolar I patients co-medicated with lithium or valpromide. A randomized controlled trial is planned to confirm these results.

Agomelatine: a preliminary review of a new antidepressant

Agomelatine is a new antidepressant that is a potent agonist of melatonin receptors and an antagonist of the serotonin 5-HT(2C) receptor subtype. It is in late-phase trials for the treatment of major depressive disorder (MDD). Symptoms of depression significantly improved with agomelatine compared with placebo in large placebo-controlled trials, and agomelatine appears to be as efficacious in treating MDD as other antidepressants but with fewer adverse effects. Agomelatine appears to improve sleep quality and ease of falling asleep, as measured subjectively in depressed patients. Polysomnographic studies have shown that agomelatine decreases sleep latency, decreases wake after sleep onset (WASO), and improves sleep stability as measured by changes in the cyclic alternating pattern. Agomelatine is generally well tolerated in patients with MDD; in clinical trials, adverse events were generally mild to moderate in nature, with an overall frequency close to that of placebo. Discontinuation of agomelatine because of adverse effects occurred at a similar rate to placebo.

Agomelatine: an antidepressant with a novel mechanism of action

Despite advances in understanding potential disease mechanisms in depression and in therapeutic approaches to the management of major depressive disorder, the disease continues to carry an enormous personal, social and economic burden. Agomelatine is a melatonergic antidepressant with melatonin (MT1 and MT2) agonistic and serotonin (5-HT2C) antagonistic properties. It represents a promising approach to treating depression through a unique synergistic mechanism. There is also preliminary evidence to suggest that agomelatine has anxiolytic properties in depressed patients. Clinical data confirm that agomelatine, in a dose range of 25–50 mg daily, is an effective antidepressant with a very favorable side-effect profile. In particular, sleep restorative effects in the absence of daytime sedation and a favorable effect on sexual function suggest that agomelatine will offer a high efficacy–tolerability index for patients with major depressive disorder. Such results have been anticipated based on preclinical studies using various animal models of both depression and anxiety.

Drug treatment of depression in the 2000s: An overview of achievements in the last 10 years and future possibilities

During the past 10 years our knowledge about the pharmacotherapy of depression has been consolidated, and a variety of very interesting new compounds launched onto the market. The pipeline of the pharmaceutical industry is still filled with an assortment of new developments and very promising new approaches towards the pharmacotherapy of depressive disorders. Future pharmacological treatments of depression will not only enhance serotonergic and noradrenergic neurotransmission: other systems, such as the melatonergic receptor system and the hypothalamus-pituitary-adrenal axis, are also the targets of newly developed and upcoming substances with putative antidepressant effects. The main advantages of the currently available newer pharmacotherapeutic options are the broadening of the spectrum of possible antidepressant treatments, which is of particular importance for the growing number of patients suffering from difficult-to-treat depression, and a far better tolerability profile in comparison to older compounds such as tricyclic antidepressants. Unresolved issues are the unacceptably high rate of non-responsiveness during antidepressant treatment, a latency of sometimes several weeks until clinical improvement and remission can be achieved, and a variety of possible side effects also present during treatment with modern compounds. This review mainly presents the development of antidepressant pharmacotherapies during the past 10 years, together with pharmacokinetic and pharmacodynamic information and a comparison of different pharmacological treatment principles evaluated in randomized controlled clinical trials. In addition, new pharmacological strategies that are not yet available on the market and strategies currently under development are reviewed in detail. The study of new treatment options is of major importance to provide better strategies for the clinical management of depression in the future, and is thus also of great socio-economic importance.

Potential Medical and Surgical Complications of Serotonergic Antidepressant Medications

Serotonergic antidepressants are the most widely used group of antidepressant medications. Although generally considered to have a favorable adverse-effect profile, serotonergic antidepressants are associated with potentially dangerous medical complications, some of which have only recently become apparent to patients and clinicians. This article reviews the association of serotonergic antidepressants and the following medical complications: syndrome of inappropriate antidiuretic hormone secretion, bleeding, serotonin syndrome, serotonin-discontinuation syndrome, and adverse pregnancy and neonatal effects. Physicians need to remain aware of these potential medical complications and integrate this information into their clinical decision-making, informed-consent process, baseline assessment, and follow-up monitoring.

Melatonin affects the immobility time of rats in the forced swim test: the role of serotonin neurotransmission

The efficacy of melatonin or its derivatives in depressive patients has been recently considered for clinical application. However, the evidence for its effect on experimental models of depression is not consolidated. Here, the effects of melatonin on the model of forced swim test (FST) paradigm were studied in male rats of the Wistar strain after acute intraperitoneal (i.p.) administration of 0.1, 0.5 or 1 mg/kg of the hormone. Melatonin at doses of 0.5 and 1 mg/kg, but not of 0.1 mg/kg, decreased the immobility of rats in the FST paradigm suggesting a possible antidepressant-like activity. The dose of 0.5 mg/kg appeared to be as potent as clomipramine 50 mg/kg in reducing the immobility time of rats in the FST paradigm. The effect of melatonin on immobility time of rats in the FST paradigm was abolished by the simultaneous injection of the non-selective melatonin antagonist, luzindole (0.25 mg/kg, subcutaneously). Similarly, administration of small quantities of serotonin (5-HT, 5 ng/1 microl) or of the 5-HT(2A)/5-HT(2C) receptor agonist 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (2 ng/1 microl) injected into the amygdale totally suppressed the reduction of immobility time in the FST paradigm induced by melatonin 0.5 mg/kg. These results may suggest that effects of melatonin on the behavioral reaction of rats in the FST paradigm are due to an interaction of the hormone with central 5-HT neurotransmission.

A double-blind, randomized, parallel-group, flexible-dose study to evaluate the tolerability, efficacy and effects of treatment discontinuation with escitalopram and paroxetine in patients with major depressive disorder

This multinational, randomized, double-blind, flexible-dose study evaluated the short- and long-term antidepressant tolerability and efficacy of escitalopram and paroxetine. Tolerability was assessed by monitoring adverse events throughout the study, and discontinuation events during brief treatment interruption and tapered withdrawal. Discontinuation-emergent effects were evaluated in two separate double-blind periods. First, to mimic the consequences of non-compliance, patients were randomized to one of two treatment interruption periods (placebo-substitution for 3-5 days). Second, patients were randomized to a 1-2-week tapered withdrawal period randomly scheduled between weeks 28 and 31. The pre-specified primary efficacy endpoint was the mean change from baseline in total Montgomery-Asberg Depression Rating Scale (MADRS) score at week 8, using the principle of last observation carried forward. A total of 323 patients entered 8 weeks of double-blind treatment and received at least one flexible dose of escitalopram (10-20 mg/day) or paroxetine (20-40 mg/day). Patients who demonstrated evidence of a significant clinical improvement (Clinical Global Impression-Improvement of 1 or 2) at week 8 entered a 19-week, double-blind maintenance period during which they were treated with the same dose they received at week 8, followed by a 1-2-week tapered withdrawal period. A total of 89 patients (28%) withdrew during the study; significantly (P<0.01) more patients withdrew from the paroxetine group (34%) than from the escitalopram group (21%), and significantly (P<0.05) more paroxetine patients withdrew due to lack of efficacy. The mean MADRS total score improved for both treatment groups from baseline to week 8, with no statistical difference between groups. In severely depressed patients (baseline MADRS total score >or=30), escitalopram was superior (P<0.05) to paroxetine at week 27 (end of maintenance treatment). There was a high prevalence of sexual dysfunction at baseline: the mean Arizona Sexual Experience Scale (ASEX) score was approximately 20 points in both treatment groups. Mean total ASEX scores increased slightly above baseline values during the acute period and declined slightly below baseline values towards the end of the maintenance period. During taper and cessation of treatment, patients in the paroxetine group demonstrated significantly more discontinuation symptoms relative to escitalopram based on the Discontinuation Emergent Signs and Symptoms scores.

Multi-target strategies for the improved treatment of depressive states: Conceptual foundations and neuronal substrates, drug discovery and therapeutic application

Major depression is a debilitating and recurrent disorder with a substantial lifetime risk and a high social cost. Depressed patients generally display co-morbid symptoms, and depression frequently accompanies other serious disorders. Currently available drugs display limited efficacy and a pronounced delay to onset of action, and all provoke distressing side effects. Cloning of the human genome has fuelled expectations that symptomatic treatment may soon become more rapid and effective, and that depressive states may ultimately be "prevented" or "cured". In pursuing these objectives, in particular for genome-derived, non-monoaminergic targets, "specificity" of drug actions is often emphasized. That is, priority is afforded to agents that interact exclusively with a single site hypothesized as critically involved in the pathogenesis and/or control of depression. Certain highly selective drugs may prove effective, and they remain indispensable in the experimental (and clinical) evaluation of the significance of novel mechanisms. However, by analogy to other multifactorial disorders, "multi-target" agents may be better adapted to the improved treatment of depressive states. Support for this contention is garnered from a broad palette of observations, ranging from mechanisms of action of adjunctive drug combinations and electroconvulsive therapy to "network theory" analysis of the etiology and management of depressive states. The review also outlines opportunities to be exploited, and challenges to be addressed, in the discovery and characterization of drugs recognizing multiple targets. Finally, a diversity of multi-target strategies is proposed for the more efficacious and rapid control of core and co-morbid symptoms of depression, together with improved tolerance relative to currently available agents.

Prospects for the treatment of depression

Antidepressant drugs represent the principal form of treatment for major depressive disorder. While there are a plethora of medications available for this task, current drugs have many shortcomings. In the face of these deficiencies there is an ongoing search for new agents. The search has been guided, in part, by drug design based on existing agents and their putative mechanism of action. This has been less than fruitful in addressing inadequacies of existing medications as it has not produced compounds which are novel in terms of pharmacological mechanisms. Recent insights from molecular biological approaches hold promise for the discovery of novel compounds, in particular the so-called neurogenesis hypothesis suggests novel therapeutic approaches. Although significantly modified over the years, the monoamine hypothesis of depression and antidepressant drug action still remains an important driving force behind the development of new compounds. Several recently marketed agents and some in early-phase development tend to conform to these existing mechanistic hypotheses. Clearly the place of these agents in the treatment of depression is dependent on issues such as short- and long-term safety and efficacy. Duloxetine has been developed as a dual monoamine re-uptake inhibitor. Agomelatine is a compound with major effects on the circadian system as well as effects on subtypes of the serotonin receptor system. While the mechanism of action of this compound is not certain, recent evidence would suggest that the drug exerts its effects through antagonist actions at serotonin receptors. Compounds based on the hypothalamic pituitary adrenal axis, substance P antagonism and other neuropeptides have potential application for the treatment of depression but require further development before that potential is realized.

Serotonin 5-HT2C receptors as a target for the treatment of depressive and anxious states: focus on novel therapeutic strategies

Serotonin (5-HT)2C receptors play an important role in the modulation of monoaminergic transmission, mood, motor behaviour, appetite and endocrine secretion, and alterations in their functional status have been detected in anxiodepressive states. Further, 5-HT2C sites are involved in the actions of several classes of antidepressant. At the onset of treatment, indirect activation of 5-HT2C receptors participates in the anxiogenic effects of selective 5-HT reuptake inhibitors (SSRIs) as well as their inhibition of sleep, sexual behaviour and appetite. Conversely, progressive down-regulation of 5-HT2C receptors parallels the gradual onset of clinical efficacy of SSRIs. Other antidepressants, such as nefazodone or mirtazapine, act as direct antagonists of 5-HT2C receptors. These observations underpin interest in 5-HT2C receptor blockade as a strategy for treating depressive and anxious states. This notion is supported by findings that 5-HT2C receptor antagonists stimulate dopaminergic and adrenergic pathways, exert antidepressant and anxiolytic actions in behavioural paradigms, and favour sleep and sexual function. In addition to selective antagonists, novel strategies for exploitation of 5-HT2C receptors embrace inverse agonists, allosteric modulators, ligands of homo/heterodimers, modulators of interactions with 'postsynaptic proteins', dual melatonin agonists/5-HT2C receptor antagonists and mixed 5-HT2C/alpha2-adrenergic antagonists. Intriguingly, there is evidence that stimulation of regionally discrete populations of 5-HT2C receptors is effective in certain behavioural models of antidepressant activity, and promotes neurogenesis in the hippocampus. This article explains how these ostensibly paradoxical actions of 5-HT2C antagonists and agonists can be reconciled and discusses both established and innovative strategies for the exploitation of 5-HT2C receptors in the improved management of depressed and anxious states.

Efficacy and tolerance profile of agomelatine and practical use in depressed patients

Agomelatine is a new agent with a unique pharmacological profile, as the first melatonergic antidepressant. Its antidepressant efficacy has been demonstrated in the treatment of major depressive disorder (MDD) at a dose of 25 mg/day. Expectations from antidepressant therapies now go beyond efficacy alone, to include advantages in tolerability and safety. Due to its pharmacological profile, agomelatine does not induce the side-effects typical of other therapies, such as selective serotonin reuptake inhibitors (i.e. gastrointestinal disorders, weight gain, serotonergic syndrome and insomnia). Moreover, a placebo-controlled trial in MDD comparing the effects of agomelatine and venlafaxine on sexual dysfunction (another significant side-effect with current antidepressant medications) indicated the very favourable profile of agomelatine; in the same study, there was similar antidepressant efficacy in the same two groups. A double-blind, placebo-controlled trial investigating the effect of abrupt cessation of treatment demonstrated the absence of discontinuation symptoms with agomelatine, which was in contrast with the results observed with paroxetine. The ability of an antidepressant to relieve sleep complaints with no sedative effects is a key advantage because sleep complaints are a major presenting feature of depression. Again due to its unique pharmacological profile, agomelatine has been shown to positively influence disturbed circadian rhythms in depressed patients by significantly improving all phases of disturbed sleep and the overall quality of sleep, with a favourable impact on daytime alertness. In conclusion, experience with agomelatine across a range of clinical studies suggests that this compound offers a novel approach to the treatment of depression combining efficacy, even in severe depression, with an extremely favourable side-effect profile and sleep regulation. These properties give agomelatine a definite clinical advantage in the treatment of depression.

Placebo-controlled trial of agomelatine in the treatment of major depressive disorder

The efficacy and safety of flexible dosing with the antidepressant agomelatine (25-50 mg/day) was evaluated in a 6-week, double-blind, randomized, placebo-controlled study involving 212 patients who met Diagnostic and Statistical Manual of Mental Disorders-Fourth Edition (DSM-IV) criteria for major depressive disorder-current major depressive episode. Patients receiving agomelatine (25 mg and 50 mg/day) had a significantly lower mean Hamilton Rating Scale for Depression (HAM-D) score at endpoint compared with those who received placebo (14.1 +/- 7.7 vs. 16.5 +/- 7.4, p = 0.026). Agomelatine significantly improved the response rate (49.1%; p = 0.03), time to first response (p = 0.032), and Clinical Global Impression-Severity of Illness score (p = 0.017), compared with placebo. These results were confirmed in a subgroup of patients with greater symptom severity. Agomelatine 50 mg also appeared to be effective and well tolerated in patients who failed to show improvement after 2 weeks on a dose of 25 mg/day. These results support the prescription of agomelatine 25 mg as the usual therapeutic dose, and suggest that increasing the dose to 50 mg may be beneficial for some patients without reducing tolerability.

Why do we need new and better antidepressants?

The range of available antidepressants is reviewed in relation to mechanisms of action and the evidence of efficacy in general and efficacy in severe depression in particular. In studies investigating efficacy in major depressive disorder, not all antidepressants have been shown to have clear-cut efficacy in severe depression. Here, the minimum standards for the necessary methodology to investigate efficacy in severe depression are reviewed and the methods that are needed to establish efficacy as a superior antidepressant or as an antidepressant with a faster than expected response are suggested. A review of the mechanisms of action of different antidepressants is accompanied by a critical review of the properties of an antidepressant likely to achieve either efficacy in severe depression or the status of a superior antidepressant.

Clinical efficacy of agomelatine in depression: the evidence

Despite the advances of recent decades, there is still an urgent need for antidepressants with improved efficacy, safety and tolerability. Agomelatine is a new antidepressant with an innovative pharmacological profile. It is the first melatonergic antidepressant, and is a potent agonist of melatonin receptors (MT1 and MT2) with 5-HT2C antagonist properties. The efficacy of 25 mg/day agomelatine in treating major depressive disorder (MDD) has been demonstrated in a number of placebo-controlled studies. Evidence of improvement in depressive symptoms was observed in a dose-ranging study in which 25 mg/day agomelatine was significantly better than placebo, whatever the rating scale used (Hamilton Rating Scale for Depression, Clinical Global Impression, and Montgomery-Asberg Depression Rating Scale). These results have been confirmed in two similarly designed placebo-controlled studies. Agomelatine also produces a significant improvement in anxiety compared to placebo, according to Hamilton Rating Scale for Anxiety scores. The efficacy of agomelatine has been studied in subpopulations with more severe depression, demonstrating its efficacy in these difficult-to-treat patients. In view of the available data on agomelatine, this antidepressant can be regarded as an innovative treatment for MDD patients, offering a new approach in the management of depressed patients.

Comment déveloper un antidépresseur au mécanisme d’action innovant : l’exemple de l’agomélatine

There are now many potentials for the development of more effective, better tolerated, and more rapidly acting antidepressants acting in association and/or beyond the monoamine hypothesis. One of these possibilities is the development of antidepressant drugs with melatonin agonist property. This holds much promise since various affective disorders, including depression, are characterized by abnormal patterns of circadian rhythms. In line with this, the melatoninergic agonist properties of agomelatine, an antidepressant with proven clinical efficacy, may represent a new concept for the treatment of depression. By way of behavioral studies in rodents, it has been shown that administration of agomelatine can mimic the action of melatonin in the synchronization of circadian rhythm patterns. Interest in agomelatine has increased in recent times due to its prospective use as a novel antidepressant agent, as demonstrated in a number of animal studies using well-validated animal models of depression (including the forced swimming test, the learned helplessness, the chronic mild stress). Interestingly, the melatoninergic agonist property of agomelatine may not, alone, be sufficient to sustain its clear antidepressant-like activity. Recent results from receptor binding and in vivo studies gave support to the notion that agomelatine's effects are also mediated via its function as a competitive antagonist at the 5-HT2C receptor. Finally, thanks to its absence of binding with a broad range of receptors and enzymes, agomelatine is particularly safe and devoid of all the deleterious effects reported with tricyclics and SSRIs.