Selective Serotonin 5-HT2A Receptor Antagonists and Inverse Agonists Specifically Promote Slow Wave Sleep (Stage N3) in Man

Abstract

Several drug classes are widely prescribed when difficulties with sleep induction or sleep maintenance occur, as is the case in patients with an insomnia disorder. These include the benzodiazepine and non-benzodiazepine receptor allosteric modulators, the melanin receptor agonist ramelteon, low-dose doxepin, and the orexin receptor antagonist suvorexant. Benzodiazepines are often less than satisfactory, since they are known to produce reductions in both N3 sleep and rapid-eye movement (REM) sleep. Similarly, low-dose doxepin has been associated with a reduction in REM sleep. Initially, it was shown that the non-selective serotonin 5-HT2A/2C receptor antagonists’ ritanserin, ketanserin, seganserin, and ICI-169,369 increase N3 sleep in subjects with normal sleep. Ritanserin produced also an increase of N3 sleep in poor sleepers, patients with a chronic insomnia disorder, and psychiatric patients with a generalized anxiety disorder or a mood disorder. More recent evidence indicates that the selective 5-HT2A receptor antagonist volinanserin and the 5-HT2A receptor inverse agonists’ nelotanserin and pimavanserin significantly increase N3 sleep in subjects with normal sleep. Nelotanserin was also shown to augment N3 sleep in patients with a chronic insomnia disorder. N2 sleep tended to decrease in most of these studies, while REM sleep showed no significant changes. The present review which summarizes these findings is the basis for a proposal for a new therapeutic strategy. It is proposed that the co-administration of a selective 5-HT2A receptor antagonist or inverse agonist along with a hypnotic drug could be a valid clinical strategy for normalizing sleep induction and maintenance and for promoting N3 sleep in patients with an insomnia disorder.