Mirtazapine: a review of its use in major depression and other psychiatric disorders

Different actions for acute and chronic administration of mirtazapine on serotonergic transmission associated with raphe nuclei and their innervation cortical regions

The atypical antidepressant, mirtazapine enhances noradrenergic transmission, but its effects on serotonergic transmission remain to be clarified. The present study determined the effects of acute and chronic administration of mirtazapine on serotonergic transmissions in raphe nuclei and their innervation regions, frontal and entorhinal cortex, using multiple-probes microdialysis with real-time PCR and western blotting. Acute administration of mirtazapine did not affect extracellular serotonin level in raphe nuclei or cortex; however, chronic administration increased extracellular serotonin level in raphe nuclei without affecting that in cortex. Blockade of 5-HT1A receptor, but not that of the 5-HT2A/2C receptor, enhanced the effects of acute administration of mirtazapine on extracellular serotonin level in raphe nuclei. Chronic mirtazapine administration reduced the inhibitory function associated with somatodendritic 5-HT1A receptor in raphe nuclei, but enhanced postsynaptic 5-HT1A receptor in serotonergic innervated cortical regions. Chronic administration reduced the expression of mRNA and protein of serotonin transporter and 5-HT1A receptor in raphe nuclei, but not in the cortices. These results suggested that acute administration of mirtazapine probably activated serotonergic transmission, but its stimulatory action was abolished by activated inhibitory 5-HT1A receptor. Chronic administration of mirtazapine resulted in increased extracellular serotonin level via reduction of serotonin transporter with reduction of somatodendritic 5-HT1A autoreceptor function in raphe nuclei. These pharmacological actions of mirtazapine include its serotonergic profiles as noradrenergic and specific serotonergic antidepressant (NaSSA).

The noradrenergic action in antidepressant treatments: pharmacological and clinical aspects

Even though noradrenaline has been recognized as one of the key neurotransmitters in the pathophysiology of major depression (MD), noradrenergic compounds have been less extensively utilized in clinical practice, compared to selective serotonin reuptake inhibitors (SSRIs). The development of the first selective noradrenergic reuptake inhibitor (NRI), Reboxetine, has not substantially changed the state of the art. In addition, Atomoxetine, a relatively pure NRI used for the treatment of ADHD, has shown mixed results when administered in augmentation to depressed subjects. Through a Medline search from 2000 to 2010, the present article provides an updated overview of the main pharmacological and clinical aspects of antidepressant classes that, partially or selectively, act on the noradrenergic systems. The noradrenergic action plays an important clinical effect in different antidepressant classes, as confirmed by the efficacy of dual action antidepressants such as the serotonin noradrenaline reuptake inhibitors (SNRIs), the noradrenergic and dopaminergic reuptake inhibitor (NDRI) Bupropion, and other compounds (e.g., Mianserin, Mirtazapine), which enhance the noradrenergic transmission. In addition, many tricyclics, such as Desipramine and Nortriptyline, have prevalent noradrenergic effect. Monoamine oxidase inhibitors (MAOIs), moreover, block the breakdown of serotonin, noradrenaline, dopamine and increase the availability of these monoamines. A novel class of antidepressants--the triple reuptake inhibitors--is under development to selectively act on serotonin, noradrenaline, and dopamine. Finally, the antidepressant effect of the atypical antipsychotic Quetiapine, indicated for the treatment of bipolar depression, is likely to be related to the noradrenergic action of its metabolite Norquetiapine. Even though a pure noradrenergic action might not be sufficient to obtain a full antidepressant effect, a pronoradrenergic action represents an important element for increasing the efficacy of mixed action antidepressants. In particular, the noradrenergic action seemed to be related to the motor activity, attention, and arousal.

Pancreatic cancer and depression: myth and truth

BACKGROUND

Various studies reported remarkable high incidence rates of depression in cancer patients compared with the general population. Pancreatic cancer is still one of the malignancies with the worst prognosis and therefore it seems quite logical that it is one of the malignancies with the highest incidence rates of major depression.However, what about the scientific background of this relationship? Is depression in patients suffering from pancreatic cancer just due to the confrontation with a life threatening disease and its somatic symptoms or is depression in this particular group of patients a feature of pancreatic cancer per se?

DISCUSSION

Several studies provide evidence of depression to precede the diagnosis of pancreatic cancer and some studies even blame it for its detrimental influence on survival. The immense impact of emotional distress on quality of life of cancer patients enhances the need for its early diagnosis and adequate treatment. Knowledge about underlying pathophysiological mechanisms is required to provide the optimal therapy.

SUMMARY

A review of the literature on this issue should reveal which are the facts and what is myth.

Getting the balance right: Established and emerging therapies for major depressive disorders

Major depressive disorder (MDD) is a common and serious illness of our times, associated with monoamine deficiency in the brain. Moreover, increased levels of cortisol, possibly caused by stress, may be related to depression. In the treatment of MDD, the use of older antidepressants such as monoamine oxidase inhibitors and tricyclic antidepressants is decreasing rapidly, mainly due to their adverse effect profiles. In contrast, the use of serotonin reuptake inhibitors and newer antidepressants, which have dual modes of action such as inhibition of the serotonin and noradrenaline or dopamine reuptake, is increasing. Novel antidepressants have additive modes of action such as agomelatine, a potent agonist of melatonin receptors. Drugs in development for treatment of MDD include triple reuptake inhibitors, dual-acting serotonin reuptake inhibitors and histamine antagonists, and many more. Newer antidepressants have similar efficacy and in general good tolerability profiles. Nevertheless, compliance with treatment for MDD is poor and may contribute to treatment failure. Despite the broad spectrum of available antidepressants, there are still at least 30% of depressive patients who do not benefit from treatment. Therefore, new approaches in drug development are necessary and, according to current research developments, the future of antidepressant treatment may be promising.

Tapering clonazepam in patients with panic disorder after at least 3 years of treatment

High-potency benzodiazepines, such as clonazepam, are frequently used in the treatment of panic disorder (PD) because of their rapid onset of action and good tolerability. However, there is concern about their potential to cause withdrawal symptoms. We aimed to develop a protocol for safely tapering off clonazepam in patients with PD who had been receiving treatment for at least 3 years. A specific scale for judging withdrawal was also developed, the Composite Benzodiazepine Discontinuation Symptom Scale. We selected 73 patients with PD who had been asymptomatic for at least 1 year and who wished to discontinue the medication. The trial consisted of a 4-month period of tapering and an 8-month follow-up period. The dosage of clonazepam was decreased by 0.5 mg per 2-week period until 1 mg per day was reached, followed by a decrease of 0.25 mg per week. The mean dosage at the start of tapering was 2.7 +/- 1.2 mg/d. In total, 51 (68.9%) of the patients were free of the medication after the 4 months of tapering according to the protocol, and 19 (26.0%) of the patients needed another 3 months to be free of medication. Clonazepam discontinuation symptoms were mostly mild and included mainly: anxiety, shaking/trembling/tremor, nausea/vomiting, insomnia/nightmares, excessive sweating, tachycardia/palpitations, headache, weakness, and muscle aches. The improvement in PD and general well-being was maintained during both the taper and follow-up phases. Clonazepam can be successfully discontinued without any major withdrawal symptoms if the dose is reduced gradually. We recommend reducing the dosage of clonazepam after intermediate-term use by 0.25 mg/wk.

Impact of the novel antidepressant agomelatine on disturbed sleep-wake cycles in depressed patients

BACKGROUND

Disturbance of sleep-wake cycles is common in major depressive disorder (MDD), usually as insomnia, but also as hypersomnia or reduced daytime alertness. Agomelatine, an MT(1) and MT(2) receptor agonist and 5-HT(2C) receptor antagonist, represents a novel approach in MDD, with proven antidepressant efficacy and a positive impact on the sleep-wake cycle. We review the effects of agomelatine 25/50 mg/day on objective and subjective measures of the sleep-wake cycle in MDD.

SUBJECTIVE MEASURES

Agomelatine improved all aspects of the sleep-wake cycle from as early as 1 week in randomized trials versus selective serotonin reuptake inhibitors and venlafaxine, particularly getting off to sleep and quality of sleep, with an improvement in daytime alertness.

OBJECTIVE MEASURES

Agomelatine's effect on sleep architecture in MDD has been measured by polysomnography (PSG). There were significant improvements in sleep efficiency, slow-wave sleep (SWS), and the distribution of delta activity throughout the night, but no change in amount or latency of rapid eye movement (REM) sleep. Furthermore, the slow-wave sleep was resynchronized to the first sleep cycle of the night.

CONCLUSION

Agomelatine, a novel antidepressant, improves disturbed sleep-wake cycles in MDD. The improvement of both nighttime sleep and daytime functioning with agomelatine are promising features of this antidepressant regarding the management of MDD.

The putative antidepressant DOV 216,303, a triple reuptake inhibitor, increases monoamine release in the prefrontal cortex of olfactory bulbectomized rats

The first line of antidepressant treatment nowadays are selective serotonin reuptake inhibitors. Although they are relatively safe to use, selective serotonin reuptake inhibitors (SSRIs) can induce severe side effects. New promising antidepressants may be the triple monoamine reuptake inhibitors, which not only enhance serotonin and norepinephrine neurotransmission, but also increase brain dopamine levels. Recently it has been shown that one of the triple reuptake inhibitors, DOV 216,303 has antidepressant-like effects in the olfactory bulbectomy (OBX) model of depression, but the alterations in monoaminergic neurotransmission in these animals are still unknown. In the present study we investigated not only the effect of acute, but also chronic treatment of DOV 216,303 in OBX rats on monoamine and metabolite levels. The main results are decreased baseline dopamine levels in the prefrontal cortex one day after OBX, while 38days after OBX no difference could be observed in monoamine levels after vehicle treatment. Treatment with DOV 216,303 leads to increased extracellular levels of serotonin and norepinephrine neurotransmission, but also increased dopamine levels in OBX animals as well as their controls. This increase could be observed after one single administration, but also after chronic treatment. However, a DOV 216,303 challenge in chronically treated animals resulted in lower monoamine concentrations than the same challenge in untreated animals. More research is needed to investigate this seemingly hyporesponsivity to chronic DOV 216,303 treatment.

The effect of mirtazapine add on therapy to risperidone in the treatment of schizophrenia: a double-blind randomized placebo-controlled trial

It has been reported that mirtazapine would be helpful for treating negative symptoms in schizophrenia. Nevertheless, the results are contradictory so far. This study was designed to investigate the effect of mirtazapine added to risperidone as augmentation therapy in patients with chronic schizophrenia and prominent negative symptoms in a double-blind and randomized clinical trial. Eligible participants in the study were 40 patients with chronic schizophrenia with ages ranging from 19 to 49 years. All patients were inpatients and were in the active phase of the illness, and met DSM-IV-TR criteria for schizophrenia. Patients were allocated in a random fashion 20 to risperidone 6 mg/day plus mirtazapine 30 mg/day and 20 to risperidone 6 mg/day plus placebo. The principal measure of the outcome was Positive and Negative Syndrome Scale (PANSS). The mirtazapine group had significantly greater improvement in the negative symptoms and PANSS total scores over the eight-week trial. Therapy with 30 mg/day of mirtazapine was well tolerated and no clinically important side effects were observed. The present study indicates mirtazapine as a potential combination treatment strategy for chronic schizophrenia particularly for negative symptoms.

New approaches to the pharmacological management of major depressive disorder

Despite effective and safe therapies for major depressive disorder (MDD), the current arsenal of antidepressant therapies does not fully satisfy the needs of patients or physicians. Many patients are only partial responders or are treatment resistant and side effects interfere with compliance. The majority of antidepressants directly affect monoamine neurotransmission within the central nervous system. Moving beyond this mechanism has been a challenge because of the lack of knowledge about the underlying etiology and pathophysiology of MDD. Provided in this report is a review of some of the major new advances in MDD research that suggest the possibility of novel and improved future therapeutic options. Emphasis is placed on studies of unipolar, but not bipolar, depression. New therapies include dual and triple monoamine uptake inhibitors, non-conventional antidepressants such as tianeptine, and a number of augmentation strategies. In addition, studies are underway on a number of mechanisms of action that might yield the next therapeutic advance. These include agents that interact with endocannabiniod systems, examination of natural products, and compounds that influence neuropeptide systems such as galanin and melanin-concentrating hormone, and growth and neurotrophic factors. Epigenetic mechanisms involving histone modification are also being explored. An area of intensive investigation is glutamate neurotransmission. Data support the hypothesis that NMDA receptor antagonists are effective in MDD individuals resistant to conventional therapies. The potential of metabotropic glutamate receptors as novel targets is also discussed. Accumulating evidence supports the idea that amplification of AMPA receptor function is a critical link in the transduction processes involved antidepressant effects.