Melatonin
Other Names: MEL, MLT, N-acetyl-5-methoxytryptamine
Should I take it?
Melatonin is a natural hormone primarily produced by the pineal gland of mammals. In humans, the pineal gland is a very small organ located in the brain. Sensitive to light, it produces melatonin only during darkness--with production increasing approximately an hour or so before an individual?s customary sleeping times and then decreasing before usual awakening times. It is now believed that other body tissues, such as the gastrointestinal tract, the retinas, and the skin, also produce small amounts of melatonin. Children begin producing melatonin at about 3 months of age. Its production increases until about age 20 and then drops off as individuals age. By age 80, natural melatonin levels are estimated to be only about 20% of their peak levels. Melatonin production also appears to be reduced in conditions such as dementia, which are usually associated with aging.
In humans, melatonin affects daily cycles, also called circadian rhythms, such as sleep and body temperature. In other mammals, melatonin plays a role in seasonal changes such as hibernation. Melatonin also seems to promote growth and sexual maturity and it may assist in maintaining balance. Low levels of melatonin have been reported in individuals with autism spectrum disorder, depression, fibromyalgia, insomnia, some seizure disorders, and other conditions.
Supplemental melatonin should be synthetic--derived from sources that are not animal or human. In the past, some melatonin products were made from animal tissue, which carried the risk of possible contamination with viruses and other toxins. Because of concerns with contamination and safety, Japan currently prohibits the sale of melatonin supplements and Britain restricts their use.
Dosage and Administration
In the United States, supplemental melatonin is most readily available as capsules and tablets--some in controlled-release forms that deliver measured doses of melatonin over extended periods. It also comes in a tablet that dissolves quickly under the tongue. Dosing recommendations vary considerably, with a wide range between 0.1 mg and 10 mg used in studies for various conditions. However, to promote sleep, doses over 0.5 mg generally were no more effective than lower doses. In clinical studies, melatonin has been used for as long as 9 months, but most commonly it is used for a few days at a time. Individuals who choose to use melatonin should follow exactly the directions for the condition they are treating. Common recommendations for its use include:
Insomnia: 0.3 mg to 5 mg at bedtime (for children over 10 years of age, no more than 3 mg)
Jet lag: 0.5 mg to 5 mg at bedtime for up to 5 days, beginning on the day before the trip
Benzodiazepine withdrawal: 2 mg controlled-release daily at bedtime for 6 weeks as the benzodiazepine dose is gradually decreased
Smoking cessation: 0.3mg taken 3 hours to 4 hours after the last cigarette
Individuals who choose to use melatonin should follow exactly the directions on the package of the product that is purchased.
Summary
In the United States, melatonin is used mainly for regulating disturbed sleep that may be caused by traveling across multiple time zones or changing shifts at work. Melatonin may also have limited usefulness for treating some types of cancer, helping individuals dependent on benzodiazepines to withdraw from the drugs, and assisting smokers to quit smoking. Other uses may include preventing both cluster headaches and sunburn. However, it has not yet been found effective for any of these uses.
Risks
Melatonin may affect fertility in women trying to conceive, and not enough is known about its potential effects on fetal and infant development and growth to recommend it for pregnant or breast-feeding women. Because natural melatonin appears to have an effect on sexual development, supplemental melatonin should not be given to children. Melatonin should also be avoided by individuals with liver conditions, because it may accumulate in the blood--possibly causing side effects. Individuals with bipolar or depressive disorders should only use supplemental melatonin if a doctor recommends it because melatonin may cause or worsen symptoms of depression. Because melatonin can cause drowsiness, individuals who take it should be careful when performing tasks that require alertness.
Side Effects
Melatonin may affect the body's production and use of some hormones. In addition, it can cause:
- Abdominal cramps, nausea, and vomiting
- Confusion, drowsiness, and dizziness
- Headache and irritability
- Low blood pressure
Interactions
Melatonin may interfere with the effectiveness of:
- Antidepressants
- Corticosteroids
- Drugs for high blood pressure
- Immunosuppressants
- Sedatives
Melatonin may also increase sleepiness caused by some prescription, non-prescription, and herbal products and by alcohol. Caffeine may decrease the effectiveness of melatonin.
Last Revised April 15, 2008
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Should I take it? 
