Does agomelatine have a place in the treatment of depression?

Agomelatine: An astounding sui-generis antidepressant?

Major depressive disorder (MDD) is one of the foremost causes of disability and premature death worldwide. Although the available antidepressants are effective and well tolerated, they also have many limitations. Therapeutic advances in developing a new drug's ultimate relation between MDD and chronobiology, which targets the circadian rhythm, have led to a renewed focus on psychiatric disorders. In order to provide a critical analysis about antidepressant properties of agomelatine, a detailed PubMed (Medline), Scopus (Embase), Web of Science (Web of Knowledge), Cochrane Library, Google Scholar, and PsycInfo search was performed using the following keywords: melatonin analog, agomelatine, safety, efficacy, adverse effects, pharmacokinetics, pharmacodynamics, circadian rhythm, sleep disorders, neuroplasticity, MDD, bipolar disorder, anhedonia, anxiety, generalized anxiety disorder (GAD), and mood disorders. Agomelatine is a unique melatonin analog with antidepressant properties and a large therapeutic index that improves clinical safety. It is a melatonin receptor agonist (MT1 and MT2) and a 5-HT2C receptor antagonist. The effects on melatonin receptors enable the resynchronization of irregular circadian rhythms with beneficial effects on sleep architectures. In this way, agomelatine is accredited for its unique mode of action, which helps to exert antidepressant effects and resynchronize the sleep-wake cycle. To sum up, an agomelatine has not only antidepressant properties but also has anxiolytic effects.

The preclinical discovery and development of agomelatine for the treatment of depression

INTRODUCTION

Under the treatment of commonly used antidepressants, many patients with major depressive disorder (MDD) do not achieve remission. All previous first-line treatments for depression have focused on the enhancement of monoaminergic activity. Agomelatine was the first antidepressant with a mechanism of action extending beyond monoaminergic neurotransmission.

AREAS COVERED

The aim of this case history is to describe the discovery strategy and development of agomelatine. The pharmacodynamic profile of the drug is briefly presented. The article summarizes (a) the preclinical behavioral data on agomelatine's effects on depressive-like behavior, anxiety, and circadian rhythmicity disruptions, and (b) the results of early preclinical studies on safety, efficacy in MDD, and the risk-benefit pharmacological profile. Furthermore, the article examines findings of post-marketing research on safety, efficacy, and cost-effectiveness of the drug.

EXPERT OPINION

There is now evidence supporting the clinical efficacy and safety profile of agomelatine in the acute-phase treatment of MDD. Agomelatine may be more effective in specific subgroups of MDD patients, those with severe anxiety symptoms or disturbed circadian profiles. Its antidepressant and anxiolytic activities are due to synergy between its melatonergic and 5-hydroxytryptaminergic effects. Since its discovery, novel compounds acting on the melatonergic system have been under investigation for the treatment of MDD.

Agomelatine for depression: expanding the horizons?

INTRODUCTION

Agomelatine is an antidepressant with unique pharmacological actions; it is both a melatonin agonist and selective serotonin antagonist. Both actions combined are necessary for antidepressant efficacy. Effects on melatonin receptors enable resynchronisation of disrupted circadian rhythms with beneficial effects on sleep patterns. Areas covered: The issue of use of an antidepressant for depression co-morbid with somatic disorders is covered by the authors. A review of the literature from 2000 to August 2018 was undertaken using Scopus and Web of Science with the key words: agomelatine, depression, medical illness. Depression in Parkinson's disease, cardiovascular illness and type II diabetes is reviewed with evidence of efficacy. Bipolar depression and seasonal affective disorder may also react favourably. Agomelatine may have specific efficacy on symptoms of anhedonia. Expert opinion: Despite approval in some major jurisdictions, the drug has failed to gain registration in the United States. A defining issue may be questions about longer term efficacy: unequivocal effectiveness in placebo-controlled relapse prevention studies has not always been demonstrated. Continuation studies suggest maintenance of clinical responsiveness. A major disadvantage of the drug is its' potential hepatotoxicity and the need for repeated clinical laboratory tests.

Motivational interviewing: living up to its promise?

Motivational interviewing is a form of psychotherapy in which ambivalence towards an aberrant behaviour is targeted. Rather than challenge the behaviour directly, the clinician encourages the patient to devise a list of problems that are caused by the behaviour and to identify solutions. There are many trials of motivational interviewing, although it has been most studied as treatment for substance misuse. The effect sizes for motivational interviewing are small, they probably diminish over time, the trials often use multiple outcome measures and the outcomes of some very large trials have been disappointing. Large effects are occasionally reported, although these tend to be from small trials conducted by highly motivated research groups and the results tend to diminish when the trials are repeated or enlarged. Nonetheless, motivational interviewing is a well-validated approach supporting and enabling engagement in therapeutic process. It could be argued that even though it might not be as efficacious as a primary/stand-alone means of changing patients’ behaviour, it can still be highly effective when combined with other approaches or used as a conduit to a more intensive therapy.

LEARNING OBJECTIVES

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DECLARATION OF INTEREST

None.

Drug and alcohol addiction: do psychosocial treatments work?

Methodological issues such as social desirability bias, subjective outcome measures, therapist enthusiasm and fidelity to the intervention remain a major problem in assessing the effectiveness of psychosocial treatments for substance misuse. Alcoholics Anonymous and other 12-step programmes are still widely used, although it is difficult to formally assess their effectiveness. Motivational interviewing is perhaps the most commonly used professional psychosocial treatment for substance misuse, but brief interventions based on this technique report a disappointing effect size (∼0.2). Contingency management is perhaps the most effective reported modality, although it remains politically controversial. Cognitive—behavioural therapy and community reinforcement have been widely studied, but the results are often disappointing (effect sizes seldom exceed 0.5, despite very large trials). Residential rehabilitation remains an established treatment, but patient selection prevents formal cost-effectiveness studies.

Therapeutic effects of melatonin receptor agonists on sleep and comorbid disorders

Several melatonin receptors agonists (ramelteon, prolonged-release melatonin, agomelatine and tasimelteon) have recently become available for the treatment of insomnia, depression and circadian rhythms sleep-wake disorders. The efficacy and safety profiles of these compounds in the treatment of the indicated disorders are reviewed. Accumulating evidence indicates that sleep-wake disorders and co-existing medical conditions are mutually exacerbating. This understanding has now been incorporated into the new Diagnostic and Statistical Manual of Mental Disorders, 5th Edition (DSM-5). Therefore, when evaluating the risk/benefit ratio of sleep drugs, it is pertinent to also evaluate their effects on wake and comorbid condition. Beneficial effects of melatonin receptor agonists on comorbid neurological, psychiatric, cardiovascular and metabolic symptomatology beyond sleep regulation are also described. The review underlines the beneficial value of enhancing physiological sleep in comorbid conditions.