Melatonin is a hormone naturally produced by the body. It is also used pharmacologically in various disease conditions.
Orally administered melatonin, available as pills is rapidly absorbed and the blood levels peak 60-150 minutes after ingesting the pill. After a typical pulse of secretion from the body’s own pineal gland the peak takes longer and is lesser pronounced than when pills are administered (350-10,000 times).
Of the oral pills, 10-56 percent is actively absorbed. The chemical is metabolized in the liver and it takes 12 to 48 minutes for half of the initial amount in blood to be excreted.
Melatonin is used to treat circadian rhythm sleep disorders and some types of insomnia. Melatonin helps the elderly maintain a normal sleep wake cycle. Melatonin significantly increases total sleep time in people suffering from sleep restriction.
Melatonin helps in regularising the sleep wake cycles in persons who travel to different time zones and suffer from jet lag. In these patients melatonin pills taken in the evening, together with bright light therapy upon awakening, helps in delayed sleep phase syndrome (DSPS) and non-24-hour sleep-wake syndrome. It is useful in people who work rotating or night shifts as well. Taken 30 to 90 minutes before bedtime, melatonin supplementation acts as a mild hypnotic or sleep inducing agent. This usage is now common in sleep and relaxation drinks.
Melatonin has been shown to play a role as an antioxidant and in several brain and nerve disorders like Alzheimer’s disease, learning and memory disorders, Parkinson’s disease and multiple sclerosis. Melatonin may also help the elderly with delirium.
Melatonin has shown promise in behavioral disorders in children like Attention Deficit hyperactivity disorder or ADHD. Patients on methylphenidate who are also administered melatonin take significantly lesser time to fall asleep.
Melatonin may help patients with migraine and cluster headaches. Studies have shown that melatonin may play a role in alleviating symptoms of depression and other mood disorders.
After the antioxidant role of melatonin was found, there have been studies to see if melatonin could prevent or treat cancers. Various cancer types have been shown to be responsive to oral melatonin (10-50 mg daily). This includes breast cancer, non-small-cell lung cancer, metastatic renal cell carcinoma or kidney cancer, hepatocellular carcinoma (liver cancer), and brain metastases from solid tumors (spread of primary cancers to the brain. Melatonin as an antioxidant may also be useful in amyotropic lateral sclerosis. As an antioxidant it may also protect from radiation.
Melatonin has shown beneficial effects in reducing blood cholesterols such as LDL cholesterol. Melatonin presence in the gallbladder has many protective properties. It helps in converting cholesterol to bile, preventing oxidative stress, removing gall stones and regulating the cholesterol that passes through the intestinal wall. Melatonin works as an energy metabolizing agent. This is especially true for body weight control in small animals.
Melatonin is available as dietary supplements, food additives and medications. As dietary supplement, it is sometimes combined with other ingredients, such as vitamins and herbal extracts, and not as a drug. The Food and Drug Administration (FDA) regulations that apply to medications are not applicable to melatonin. Melatonin has been sold in food products as relaxation drinks. The actual beneficial effects of these drinks are unknown. Melatonin is not approved as a food additive. Melatonin is available as a prolonged-release prescription drug, trade-name Circadin, manufactured by Neurim Pharmaceuticals. The European Medicines Agency (EMA) has approved Circadin 2 mg (prolonged-release melatonin) for patients over 55 years for the short-term treatment (up to 13 weeks) of primary insomnia.
Reviewed by April Cashin-Garbutt, BA Hons (Cantab)