Dr. David Lyness
A hormone that anticipates the daily onset of darkness
Eur J Anaesthesiol 2007; 24: 399-402
Patients who received between 3-5mg of Melatonin required less propofol at induction in one study.
There may be a decrease in melatonin secretion with NSAID use.
In animals, melatonin is involved in the entrainment (synchronization) of the circadian rhythms of physiological functions including sleep timing, blood pressure regulation, seasonal reproduction, and many others. Many of melatonin's biological effects in animals are produced through activation of melatonin receptors, while others are due to its role as a pervasive and powerful antioxidant, with a particular role in the protection of nuclear and mitochondrial DNA.
In animals, the primary function is regulation of day-night cycles. Human infants' melatonin levels become regular in about the third month after birth, with the highest levels measured between midnight and 8:00 am. Human melatonin production decreases as a person ages. Also, as children become teenagers, the nightly schedule of melatonin release is delayed, leading to later sleeping and waking times.
Blue light, principally around 460 to 480 nm, suppresses melatonin, proportional to the light intensity and length of exposure. Until recent history, humans in temperate climates were exposed to few hours of (blue) daylight in the winter; their fires gave predominantly yellow light. The incandescent light bulb widely used in the 20th century produced relatively little blue light.
Light containing only wavelengths greater than 530 nm does not suppress melatonin in bright-light conditions.
Wearing glasses that block blue light in the hours before bedtime may decrease melatonin loss.
Use of blue-blocking goggles the last hours before bedtime has also been advised for people who need to adjust to an earlier bedtime, as melatonin promotes sleepiness.
Melatonin is produced in darkness, thus usually at night, by the pineal gland, outside the blood brain barrier.
One SINGLE CENTRE ICU study showed that Long-term enteral melatonin supplementation may result in a decreased need for sedation, with improved neurological indicators and cost reduction. Further multicenter evaluations are required to confirm these results with different sedation protocols.
Minerva Anestesiol. 2015 Dec;81(12):1298-310. Epub 2015 May 13.
MR 30 Tablet 2mg = £15.39
2013 Meta analysis showed that melatonin decreases sleep onset latency, increases total sleep time and improves overall sleep quality.
The effects of melatonin on sleep are modest but do not appear to dissipate with continued melatonin use.
Although the absolute benefit of melatonin compared to placebo is smaller than other pharmacological treatments for insomnia, melatonin may have a role in the treatment of insomnia given its relatively benign side-effect profile compared to other agents.
Ferracioli-Oda E, Qawasmi A, Bloch MH (2013) Meta-Analysis: Melatonin for the Treatment of Primary Sleep Disorders. PLoS ONE 8(5): e63773. doi:10.1371/journal.pone.0063773
The supposed benefit is to synchronise sleeping pattern by taking melatonin to trick the body that it is now dark and time for natural sleep time.
ADULTS >55yo = 2 mg once daily
1–2 hours before bedtime for up to 13 weeks
AVOID in Autoimmune Diseases. Consult BNF for side effects.