Novel and Emerging Treatments
Targeting Melatonin Receptors
Ramelteon (Rozerem®) is an insomnia medication that binds to and activates receptors (MT1 and MT2) for melatonin (Miyamoto 2009). It has a higher affinity for the receptors than melatonin itself and a half-life of just over one hour (Turek 2004; Kato 2005; Sateia 2008). Studies have found that ramelteon is effective at reducing the amount of time it takes to fall asleep and increasing the amount of time people stay asleep (Sateia 2008; Erman 2006; Borja 2006; Zammit 2007). Few side effects have been demonstrated in humans. Studies also indicate a low potential for abuse (Sateia 2008).
Selective MT2 Drugs
The particular melatonin receptor MT2 has been shown in animal studies to be important for promoting deep sleep (Ochoa-Sanchez 2011; Spadoni 2011). Drugs that specifically target the MT2 receptor are beginning to emerge. Two of these novel medications, IIK7 and UCM765, have increased the amount of deep sleep in mice (Ochoa-Sanchez 2011; Spadoni 2011). However, human research needs to be done to confirm safety, efficacy, and potency.
5-HT2 Receptor Antagonists
Serotonin (5-hydroxytryptamine or 5-HT) is a neurotransmitter with diverse roles during sleep and wakefulness. It exerts activities by binding to and activating various 5-HT receptors whose biological roles depend on tissue distribution (e.g., central vs. peripheral), structural variations, interaction with other compounds (e.g., melatonin), and the environment (e.g., light/dark cycle) (Nonogaki 2012; Landolt 2009).
With regard to sleep, two 5-HT receptors are of particular interest: 5-HT2A and 5-HT2C. Activation of these receptors interferes with deep sleep (Landolt 2009). Therefore, some emerging therapeutics attempt to reduce signaling through these receptors to facilitate high-quality sleep (Xiong 2010; Al-Shamma 2010).
While both animal and human data suggest blocking 5-HT2A/C signaling appears to be a promising mechanism for improving sleep quality, more research is needed (Al-Shamma 2010; Xiong 2010).