Melatonin is a hormone secreted by the pineal gland in the brain that helps regulate other hormones and maintains the body's circadian rhythm. It is involved in photic regulations of various kinds, including adaptation to light intensity, daily changes of light and darkness, and seasonal changes of photoperiod lengths. Darkness stimulates the production of melatonin while light suppresses its activity. Jet lag, shift work, and poor vision can disrupt melatonin cycles. Melatonin helps control the timing and release of female reproductive hormones. Many researchers also believe that melatonin levels are related to the aging process. In addition to its hormonal actions, melatonin has strong antioxidant effects. It also helps strengthen the immune system.

Pharmacology

After administration, melatonin binds with its receptors. Two types of melatonin receptor subtypes - MT1 & MT2 have been identified in humans. Melatonin receptors are found in the brain and some peripheral organs. The MT1 subtype is present in the pars tuberalis of the pituitary gland and the suprachiasmatic nuclei of the hypothalamus. The MT2 subtype is mainly present in the retina. Increased level of Melatonin initiates neural & endocrine signals to optimize the levels of neurotransmitters e.g. increased serotonin, increased GABA & decreased dopamine, which induces & sustains sleep, as well as, maintains the body's circadian rhythm.

Melatonin is used for numerous conditions but is showing the most promise in the short-term regulation of sleep patterns, including jet lag.

Insomnia: Melatonin helps to induce sleep in people with-

• Disrupted circadian rhythms (such as those suffering from jet lag or poor vision or those who work the night shift)
• Low melatonin levels (such as some elderly and individuals with schizophrenia)
• Children with learning disabilities who suffer from insomnia.

Osteoporosis: Melatonin stimulates cells called osteoblasts that promote bone growth.

In Menopause: Melatonin helps peri- or postmenopausal women to regulate sleep patterns.

Eating disorders: Melatonin levels may play a role in the symptoms of anorexia.

Attention Deficit Hyperactivity Disorder (ADHD): it may be effective in managing sleep disturbances in children with this condition. And

Sarcoidosis

Adult:

Insomnia: 3-6 mg one hour before bedtime

Jet lag:

• 0.50 to 5 mg one hour prior to bedtime at final destination or, 1 to 5 mg 1 hour before bedtime for 2 days prior to departure and for 2 to 3 days upon arrival at final destination.
• Eastbound travel- Take a preflight early evening treatment followed by treatment at bedtime for 4 days after arrival.
• Westbound travel- Take for 4 days at bedtime when in the new time zone.

Sarcoidosis: 20 mg per day for 4 to 12 months.

Depression: 0.125 mg twice in the late afternoon, each dose 4 hours apart.

Difficulty falling asleep: 5 mg 3 to 4 hours before an imposed sleep period over a 4-weeks period.

Children (6 months to 14 years of age): For sleep disorders 0.30 mg/day

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

Possible adverse effects include headache and depression. Drowsiness may be experienced within 30 minutes after taking melatonin and may persist for 1 hour and thus may affect driving skills.

Overdose Effects

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

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

Pregnancy & Lactation

Information regarding safety and efficacy in pregnancy and lactation is not available.