Melatonin

Pronunciation
Scientific names: Melatonin, circadin, melatol

Common names: MEL

Efficacy rating:

ÒÒÒ...Positive clinical trials

Safety rating:

...Little exposure or very minor concerns.

What is Melatonin?

Melatonin is one of the hormones produced by the pineal gland in all vertebrates. It is also produced in extrapineal organs, such as the eye, GI tract, bone, skin, lymphocytes, platelets, and thymus. Early animal studies in the mid-1960s revealed its ability to affect sexual function, skin color, and other mammalian functions. In addition to being produced in vertebrates, melatonin is also found in plants, bacteria, unicellular eukaryotes, and invertebrates.

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Melatonin secretion is inhibited by environmental light and stimulated by darkness, with secretion starting at 9 PM and peaking between 2 and 4 AM at approximately 200 pg/mL. The duration of melatonin production varies throughout the year with shorter periods occurring during the summer months and longer periods occurring during the winter months. Nocturnal secretion of melatonin is highest in children and decreases with age. Studies in the 1990s have led to widely expanded uses of melatonin including easing insomnia, combating jet lag, preventing pregnancy (in large doses), protecting cells from free-radical damage, boosting the immune system, preventing cancer, and extending life.

What is it used for?

General uses

Melatonin is used for numerous conditions but has shown the most promise in short-term regulation of sleep patterns, including jet lag. Results from clinical trials are inconsistent.

What is the recommended dosage?

Jet lag Eastbound travel

A preflight, early evening treatment of melatonin should be followed by treatment at bedtime for 4 days after arrival.

Westbound travel

Melatonin for 4 days at bedtime when in the new time zone.

Sleep disorders Difficulty falling asleep

Melatonin 5 mg 3 to 4 hours before an imposed sleep period over 4 weeks.

Difficulty maintaining sleep

A high dose, repeated low doses, or a controlled-release formulation.

Children 6 months to 14 years of age with sleep disorders

Melatonin 2 to 5 mg has been used.

Thermal injury

Up to 20 mg orally/IV for 28 to 30 days then 10 mg orally daily for 1 year.

How safe is it?

Contraindications

Melatonin should not be used by patients who have autoimmune diseases.

Pregnancy/nursing

Information regarding safety and efficacy in pregnancy and lactation is lacking.

Interactions

Caffeine and fluvoxamine may increase the effects of melatonin, while melatonin may decrease the antihypertensive effect of nifedipine. Melatonin may possibly potentiate the effects of warfarin.

Side Effects

Possible adverse reactions include depression, dizziness, enuresis, excessive daytime somnolence, headache, and nausea. Drowsiness may be experienced within 30 minutes after taking melatonin and may persist for approximately 1 hour and, thus, may affect driving ability. There may be an increased risk for seizures in children with severe neurological disorders.

Toxicities

There is little or no evidence of any major toxicities with melatonin, even at high doses.

References

  1. Melatonin. Review of Natural Products. Facts & Comparisons [database online]. November 2009. Accessed February 2, 2010.

Copyright © 2009 Wolters Kluwer Health

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