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Tasimelteon was recently approved by the US Food and Drug Adminstration and will be sold under the trade name Hetlioz. Tasimelteo resets the circadian rhythm – it’s a “chronobiotic” – and restores normal sleep patterns by stimulation of the melatonin receptors in the suprachiasmatic nucleus (biological clock) area of the brain. This is useful in patients who experience insomnia due to shift work or jet lag. It is also useful in persons with delayed sleep phase syndrome (falling asleep and waking too late), advanced sleep phase syndrome (falling asleep and waking too early) along with non-24 hour sleep-wake syndrome such as occurs in the blind due to a lack of light sensitivity.
Indeed, the FDA’s 2014 approval of the drug was specifically for blind patients with non–24-hour sleep-wake disorder This follows on the 2010 FDA designatio of tasimelteon as an orphan drug for blind people circadian problems, and the European Medicines Agency also approved it as an orphan drug in 2011.
Does this mean sighted patients will be unable to get tasimelteon? When the FDA approves a medicine, it gets a “label” designation of what kind of patients and illnesses the medicine is good for. Doctors are usually allowed to prescibe the drugs “off label” to anyone they feel need it. Also, it is common for the FDA to approve a new medicine for a narrow niche of the public and, if there are few adverse reports in the following years, to expand the labeling. As it is, about 80,000 Americans are blind and may suffer from this circadian disorder and so qualify for tasimelteon.
The circadian rhythm is a complex system of hormone regulation which regulates sleep, wakefulness, and mood and influences many physiologic and metabolic processes and organ systems. An important part of the circadian rhythm is melatonin and melatonin receptors in the suprachiasmatic nucleus (a part of the brain). In a well-regulated circadian rhythm, levels of melatonin start to rise each evening with the onset of darkness, peak around midnight when a person should be normally asleep and fall dramatically during daylight hours. The circadian cycle initiates drowsiness and sleep partly by stimulating melatonin receptors in the suprachiasmatic nucleus and in tissues such as the retina and lenses of the eyes.
In clinical trials, subjects were asked to initiate sleep 5 hours before usual bedtime, simulating a 5 hour shift in time zones. Tasimelteon was shown to be better than placebo in the initiation of sleep and also led to a quicker return of the normal circadian rhythm with restoration of normal peak times of melatonin production. Harvard Medical School researchers wrote up the research here.
Unlike benzodiazepines such as diazepam (Valium) and newer drugs such as zolpidem (Ambien) Tasimelteon has demonstrated no affinity for the GABA receptor. Due to lack of GABA activity it will not be useful as sedative, anti-seizure agent, antianxiety agent or muscle relaxant but will also not have the potential for abuse or dependence, symptoms of withdrawal or rebound insomnia. Because of the lack of abuse potential, Tasimelteon will likely emerge as a non-scheduled prescription and not as a controlled substance.
Check out the story about it’s approval: FDA Okays Hetlioz (Tasimelteon) for Sleep Disorder in Blind