Melatonin

Melatonin is a hormone produced by the pineal gland. Its secretion is stimulated by darkness and inhibited by light. Secretion peaks between 2:00 a.m. and 4:00 a.m., and the degree of excretion diminishes with advancing age. Administering melatonin may regulate circadian rhythms and help regulate body temperature, cardiovascular function, and reproduction. It may also protect cells against oxidation caused by free-radical formation. Melatonin is available as synthetic or animal-derived (pineal tissue) products in tablet or lozenge form. The circadian (controlled-release) form isn’t available in the United States. Product names include Mela-T, Melatonex, and Melatonin Forte (combination).

Reported uses

Melatonin is used to treat insomnia, jet lag, shift-work disorder, blind entrainment, tinnitus, and depression. It’s also used to treat benzodiazepine withdrawal in elderly patients with insomnia. Melatonin is also used as a cancer therapy adjuvant, an immune system enhancer, an anti aging product, a contraceptive, and a prophylactic therapy for cluster headaches. Topically, it’s used for skin protection against ultraviolet light. It’s also been used for cachexia and in treatment of chemotherapy-induced thrombocytopenia.

Administration

  • For adjunctive therapy in metastatic lung cancer, dosage is 10 mg by mouth at bedtime
  • For benzodiazepine withdrawal in geriatric patients with insomnia, dosage is 2 mg by mouth of controlled-release melatonin at bedtime for 6 weeks. Benzodiazepine dosage is reduced by 50% during week 2 and by 75% during weeks 3 and 4; it’s discontinued during weeks 5 and 6. Patient may continue to require melatonin for up to 6 months for insomnia
  • As a preventative for jet lag, dosag is 5 to 8 mg by mouth at bedtime for 1 week, beginning 1 to 3 days before the fight
  • For other sleep disturbances, dosage is 0.3 to 5 mg by mouth at bedtime
  • As supportive treatment for metastati solid tumors, cachexia, and chemotherapy-induced thrombocytopenia, dosage is 10 to 50 mg by mouth at bedtime
  • Transmucosal and sublingual dosage forms more closely mimic endogenous melatonin and bypass first-pass metabolism by the liver; therefore, lower doses may be effective.

Hazards

Melatonin may cause headache, depression, daytime fatigue and drowsiness, dizziness, irritability, reduced alertness, confusion, and dysphoria. Other adverse effects include abdominal cramps, increased hormone levels, mild hypothermia, and pruritus.

Melatonin may interact with other medications. For example, its use with central nervous system (CNS) depressants may cause additive sedation; its use with benzodiazepines may enhance anxiolytic effects; and use with verapamil may increase melatonin secretion. Using melatonin with chlorpromazine may decrease clearance of melatonin, thus increasing its effects. Melatonin may interfere with immunosuppressant therapy by improving immune function. Melatonin interacts with other sedating herbs or supplements, such as 5-HTP, kava-kava, and valerian, causing increased sedation. Patients with hepatic insufficiency may have an increase in melatonin effect due to the extensive hepatic metabolism. Melatonin may increase human growth hormone levels.

Melatonin shouldn’t be used by patients taking CNS depressants. It shouldn’t be taken by patients using immunosuppressants or by women who are pregnant or breast-feeding. Melatonin shouldn’t be used by children because it may inhibit gonadal development. Melatonin is contraindicated in patients with multiple sclerosis other autoimmune diseases because it may exacer ate symptoms.

Clinical considerations

  • Monitor patient for excessive daytime drowsiness.
  • Melatoninis designated as an orphan drug for the treatment of circadian rhythm sleep disordes in blind patients with no light perception.
  • Warn patient to avoid hazardous activities until full extent of CNS depressant effects is known.
  • Advise patient planning to conceive that melatonin may have a contraceptive effect. However, it shouldn’t be used as a form of birth control.
  • Inform patient that melatonin may interfere with therapeutic effects of conventional drugs.
  • Warn patient about possible additive effects if taken with alcohol.
  • Advise patient to use only the synthetic form (not the animal-derived product) because of concerns about contamination and viral transmission.
  • Advise patient not to use melatonin for prolonged periods because safety data aren’t available.
  • Caution patient with a history of seizures to consult with a health care provider before using melatonin.
  • Tell patient to remind prescriber and pharmacist of any herbal or dietary supplement that he’s taking whenobtaining a new prescription.
  • Advise patient to consult his health care provider before using an herbal preparation because a treatment with proven efficacy may be available.

Research summary

A variety of randomized, double-blind, placebo-controlled and open-label randomized studies have indicated that melatonin is superior to placebo for indications such as jet lag, sleep disorders, cancer, cachexia, thrombocytopenia, and cluster headaches. Topical use of melatonin isn’t well documented.

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