Emerging treatments for major depression

History, background, concepts and current use of comedication and polypharmacy in psychiatry

Based on a careful literature search a review is presented of the history, background, concepts and current use of comedication and polypharmacy in psychiatry. The pros and cons of comedication and polypharmacy are presented, as well as their apparent increase in recent times. Possible reasons for the increase of comedication/polypharmacy are described. Both the potential advantages as well as the potential risks are discussed. The one sided view that all comedication/polypharmacy is nothing but problematic is questioned. Comedication/polypharmacy seems to be, among others, the current answer to the well-known limited efficacy and effectiveness of current monotherapy treatment strategies.

Duration of response after treatment of mild to moderate depression with Hypericum extract STW 3-VI, citalopram and placebo: a reanalysis of data from a controlled clinical trial

St. John's Wort (Hypericum perforatum L.) is a useful medication in the treatment of mild to moderate depression. By reanalysis of the data obtained from a total of 154 patients, who responded in a randomised, multicentric, double-blind, placebo-controlled study, to 6 weeks of treatment for an episode of moderate depression with either 20 mg citalopram or 900 mg Hypericum extract STW 3-VI, the duration of response and occurrence of relapse/recurrence were evaluated. Duration of response and occurrence of relapse/recurrence was measured by re-evaluating the responders in a controlled-clinical trial (final score of ≤10 according to HAMD at the end of the clinical trial) according to the Hamilton Rating Scale for Depression (HAMD). In total, 30 (19.5%) of the 154 responders were diagnosed with a relapse. The numbers of patients with relapses were highest in the citalopram group (14 of 54), whereas patients who were treated with Hypericum extract STW 3-VI showed the lowest relapse rate (8/54); patients from the placebo group showed a relapse rate of 8/46. No difference in the severity of relapse could be observed. The duration of response was longest for the Hypericum group (1817 days), intermediate for the citalopram group (1755 days) and shortest for the placebo group (802 days). Hypericum extract STW 3-VI is more efficient in lowering the relapse and recurrence rates of responders, when compared to citalopram and placebo. In addition, duration of response was increased in the group treated with Hypericum extract STW 3-VI.

Melatonin agonists in primary insomnia and depression-associated insomnia: are they superior to sedative-hypnotics?

Current pharmacological treatment of insomnia involves the use of sedative-hypnotic benzodiazepine and non-benzodiazepine drugs. Although benzodiazepines improve sleep, their multiple adverse effects hamper their application. Adverse effects include impairment of memory and cognitive functions, next-day hangover and dependence. Non-benzodiazepines are effective for initiating sleep but are not as effective as benzodiazepines for improving sleep quality or efficiency. Furthermore, their prolonged use produces adverse effects similar to those observed with benzodiazepines. Inasmuch as insomnia may be associated with decreased nocturnal melatonin, administration of melatonin is a strategy that has been increasingly used for treating insomnia. Melatonin can be effective for improving sleep quality without the adverse effects associated with hypnotic-sedatives. Ramelteon, a synthetic analog of melatonin which has a longer half life and a stronger affinity for MT1 and MT2 melatonergic receptors, has been reportedly effective for initiating and improving sleep in both adult and elderly insomniacs without showing hangover, dependence, or cognitive impairment. Insomnia is also a major complaint among patients suffering from depressive disorders and is often aggravated by conventional antidepressants especially the specific serotonin reuptake inhibitors. The novel antidepressant agomelatine, a dual action agent with affinity for melatonin MT1 and MT2 receptors and 5-HT2c antagonistic properties, constitutes a new approach to the treatment of major depressive disorders. Agomelatine ameliorates the symptoms of depression and improves the quality and efficiency of sleep. Taken together, the evidence indicates that MT1/MT2 receptor agonists like ramelteon or agomelatine may be valuable pharmacological tools for insomnia and for depression-associated insomnia.

Antidepressant- and anxiolytic effects of the novel melatonin agonist Neu-P11 in rodent models

AIM

To investigate the potential antidepressant and anxiolytic effects of Neu-P11, a novel melatonin agonist, in two models of depression in rats and a model of anxiety in mice.

METHODS

In the learned helplessness test (LH), Neu-P11 or melatonin (25-100 mg/kg, ip) was administered to rats 2 h before the beginning of the dark phase once a day for 5 days and the number of escape failures and intertrial crossings during the test phase were recorded. In the forced swimming test (FST), rats received a single or repeated administration of Neu-P11 (25-100 mg/kg, ip). The total period of immobility during the test phase was assessed. In the elevated plus-maze test (EPM), mice were treated with Neu-P11 (25-100 mg/kg, ip) or melatonin in the morning or in the evening and tested 2 h later. The percentage of time spent in the open arms and the open arms entries were assessed.

RESULTS

In the LH test, Neu-P11 but not melatonin significantly decreased the escape deficit and had no effect on the intertrial crossings. In the FST, a single or repeated administration of Neu-P11, either in the morning or in the evening, significantly decreased the duration of immobility. In the EPM test, Neu-P11 significantly increased the percentage of time spent in the open arms and the open arms entries irrespective to the time of administration. Melatonin was effective only when administered in the afternoon.

CONCLUSION

The results demonstrate that Neu-P11 exerts antidepressant and anxiolytic activities in rodent models.

Plasma and cerebrospinal fluid substance P in post-stroke patients with depression

AIMS

To investigate the correlation between the incidence of post-stroke depression (PSD) and the levels of substance P (SP) in the plasma and cerebrospinal fluid (CSF).

METHODS

Ninety-one stroke patients were divided into PSD (n = 46) and post-stroke (without depression) groups (n = 45). PSD must have occurred 2-4 weeks after the onset of the stroke and was determined by the Hamilton Rating Scale for Depression (HAMD). In addition, the subjects were divided into anterior (n = 67) and posterior circulation stroke groups (n = 24) based on the location of the focus as determined by computed tomography. All recruited patients were graded by the National Institutes of Health Stroke Scale (NIHSS).

RESULTS

The results included the following findings: (i) the level of plasma SP in the PSD group (58.47 +/- 14.39) was higher than that of the PS group (36.98 +/- 9.49; P = 0.000), while the level of CSF SP in the PSD group (72.13 +/- 13.06) was higher than that of the post-stroke group (37.30 +/- 12.57; P = 0.03); (ii) the level of plasma SP was positively correlated with the HAMD and NIHSS score; (iii) the level of plasma SP (38.45 +/- 12.23), the HAMD score (9.08 +/- 8.72), and the NIHSS score (3.25 +/- 1.90) of the anterior stroke group (51.21 +/- 16.27, 17.46 +/- 15.96, and 6.91 +/- 3.30, respectively) were higher than those of the posterior stroke group (38.45 +/- 12.23, 9.08 +/- 8.7, and 3.25 +/- 1.90, respectively; P = 0.017, P = 0.001, and P = 0.000, respectively).

CONCLUSIONS

SP in the plasma and CSF of patients exhibited a close correlation with neural damage and the incidence of PSD. This study also suggested that anterior hemispheric strokes may play a significant role in development of PSD.

Pathophysiology of depression: role of sleep and the melatonergic system

Profound disturbances in sleep architecture occur in major depressive disorders (MDD) and in bipolar affective disorders. Reduction in slow wave sleep, decreased latency of rapid eye movement (REM) sleep and abnormalities in the timing of REM/non-REM sleep cycles have all been documented in patients with MDD. It is thus evident that an understanding of the basic mechanisms of sleep regulation is essential for an analysis of the pathophysiology of depressive disorders. The suprachiasmatic nucleus (SCN), which functions as the body's master circadian clock, plays a major role in the regulation of the sleep/wakefulness rhythm and interacts actively with the homeostatic processes that regulate sleep. The control of melatonin secretion by the SCN, the occurrence of high concentrations of melatonin receptors in the SCN, and the suppression of electrical activity in the SCN by melatonin all underscore the major influence which this neurohormone has in regulating the sleep/wake cycle. The transition from wakefulness to high sleep propensity is associated with the nocturnal rise of endogenous melatonin secretion. Various lines of evidence show that depressed patients exhibit disturbances in both the amplitude and shape of the melatonin secretion rhythm and that melatonin can improve the quality of sleep in these patients. The choice of a suitable antidepressant that improves sleep quality is thus important while treating a depressive disorder. The novel antidepressant agomelatine, which combines the properties of a 5-HT(2C) antagonist and a melatonergic MT(1)/MT(2) receptor agonist, has been found very effective for resetting the disturbed sleep/wake cycle and in improving the clinical status of MDD. Agomelatine has also been found useful in treating sleep problems and improving the clinical status of patients suffering from seasonal affective disorder.

Dual- and triple-acting agents for treating core and co-morbid symptoms of major depression: novel concepts, new drugs

The past decade of efforts to find improved treatment for major depression has been dominated by genome-driven programs of rational drug discovery directed toward highly selective ligands for nonmonoaminergic agents. Selective drugs may prove beneficial for specific symptoms, for certain patient subpopulations, or both. However, network analyses of the brain and its dysfunction suggest that agents with multiple and complementary modes of action are more likely to show broad-based efficacy against core and comorbid symptoms of depression. Strategies for improved multitarget exploitation of monoaminergic mechanisms include triple inhibitors of dopamine, serotonin (5-HT) and noradrenaline reuptake, and drugs interfering with feedback actions of monoamines at inhibitory 5-HT(1A), 5-HT(1B) and possibly 5-HT(5A) and 5-HT(7) receptors. Specific subsets of postsynaptic 5-HT receptors mediating antidepressant actions are under study (e.g., 5-HT(4) and 5-HT(6)). Association of a clinically characterized antidepressant mechanism with a nonmonoaminergic component of activity is an attractive strategy. For example, agomelatine (a melatonin agonist/5-HT(2C) antagonist) has clinically proven activity in major depression. Dual neurokinin(1) antagonists/5-HT reuptake inhibitors (SRIs) and melanocortin(4) antagonists/SRIs should display advantages over their selective counterparts, and histamine H(3) antagonists/SRIs, GABA(B) antagonists/SRIs, glutamatergic/SRIs, and cholinergic agents/SRIs may counter the compromised cognitive function of depression. Finally, drugs that suppress 5-HT reuptake and blunt hypothalamo-pituitary-adrenocorticotrophic axis overdrive, or that act at intracellular proteins such as GSK-3beta, may abrogate the negative effects of chronic stress on mood and neuronal integrity. This review discusses the discovery and development of dual- and triple-acting antidepressants, focusing on novel concepts and new drugs disclosed over the last 2 to 3 years.