The Effects of Benzodiazepine and Nonbenzodiazepine Agents, Ramelteon, Low-dose Doxepin, Suvorexant, and Selective Serotonin 5-HT2A Receptor Antagonists and Inverse Agonists on Sleep and Wakefulness

Several agents are known to improve sleep induction and/or maintenance in patients with insomnia disorder. These include the benzodiazepine (BZD) and non-BZD receptor allosteric modulators, the melatonin receptor agonist ramelteon, low-dose doxepin, and suvorexant. One of the drawbacks of the BZDs is their known reduction in both N3 sleep [also known as slow wave sleep or delta sleep and characterized by the occurrence of slow high amplitude delta (0.5-2 Hz) waves] and rapid eye movement (REM) sleep. Low-dose doxepin has shown similar association with decrease in REM sleep. By contrast, suvorexant increases REM sleep. The available evidence tends to indicate that irrespective of their mechanisms of action, the selective serotonin 5-HT2A receptor antagonists and inverse agonists, including volinanserin, pruvanserin, and nelotanserin, when given in isolated administration, increases slow wave sleep in laboratory animals. Wakefulness and REM sleep were decreased in some studies. Moreover, subjects with normal sleep showed significant increase in N3 sleep following the administration of eplivanserin, nelotanerin, and pimavanserin. Nelotanserin has also been shown to augment N3 sleep in patients with chronic insomnia disorder. N2 sleep tended to decrease in most of these studies, while REM sleep showed no significant changes. Taken together, these evidences suggest that the coadministration of a selective 5-HT2A receptor antagonist or inverse agonist with a hypnotic drug could be a valid clinical strategy for normalizing sleep induction and maintenance and for promoting N3 sleep in patients with insomnia disorder. Additionally, the 5-HT2A receptor agents may have a potential value for improving the cognition and memory deficits in patients with a chronic insomnia disorder as well as elderly patients who show reductions in N3 sleep.