Schizophrenia is a mental dysfunction of thought, perception and behaviour which can be attributed to complex and dynamically interacting perturbations in multiple neurochemical systems. Along with these cardinal features of schizophrenia, sleep disorders and disturbed circadian rhythm are commonly encountered among patients. Markedly decreased sleep efficiency, delayed sleep onset and frequent awakenings are most common observations. Endogenous melatonin is a dependable biomarker of circadian rhythmicity and, it has already been found that the nocturnal rise of endogenous melatonin is blunted leading to circadian dysrhythmia in schizophrenia.
The antipsychotics prescribed for the condition though cause improvement in the cardinal symptoms of the disease but have no significant effect on melatonin levels. The blunted peak of night time melatonin secretion are not restored or even decreased even after several months therapy with antipsychotics. In this clinical scenario, add-on therapy with sedative/ hypnotics along with antipsychotics is mandate for a prescription. Previous studies revealed that add-on therapy with benzodiazepines can worsen the already existing derangement in circadian rhythm by decreasing secretion of nocturnal melatonin. A long term add on therapy with benzodiazepines in patients on antipsychotics has been found to have an increased risk of death.
Addition of melatonin to the pharmacotherapy of schizophrenia elevates mood and daytime functioning in addition to improved sleep in schizophrenia patients. Melatonin, apart from being a hypnotic and circadian rhythm restoring compound, also possess neuroprotective, anti-neuroinflammatory and antioxidant properties. The rate limiting step of melatonin biosynthetic pathway is the alkylation of serotonin to N- acetyl serotonin, catalyzed by enzyme AANAT (aryl-alkylamine- N-acetyl-transferase). Study of AANAT enzyme and its modulation to achieve normal rhythmical secretion of melatonin can also be a potential target for resynchronising the circadian rhythm.
Ramelteon is a melatonin receptor agonist approved for treatment of insomnia by the USFDA. It exerts its action by acting on MT1 and MT2 receptors at suprachiasmatic nucleus. The long term safety of ramelteon has been evaluated by several workers and found no significant adverse effects like abuse liability, rebound insomnia and cognitive impairment. In contrast to melatonin, it shows higher-binding affinity for MT1 and MT2 receptors, more lipophilic and has a longer half-life(t1/2 of melatonin is 20-50 min whereas that of ramelteon is 1-2.6 hrs and that of its active melabolite M-II is 2-5 hrs). In addition, ramelteon has been already evaluated as a potential adjunctive treatment for learning and memory deficits in schizophrenia.
The sleep and circadian rhythm disorders in schizophrenia have so far been given very less importance by researchers and there are limited studies targeting or modulating the melatonin pathway. Therefore, proposed study has been planned to evaluate the effect of add-on ramelteon on sleep pattern/quality and circadian rhythm disruption in patients with schizophrenia.
