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Are there any interactions with melatonin?

Melatonin is a hormone that occurs naturally in the body. It's involved in the body's biological clock, which affects your sleep cycle and your body's production of other hormones. Studies show that dietary supplements containing melatonin may help with jet lag and sleep disorders. There are also claims that melatonin supplements slow the aging process, protect the body from toxins, boost the immune system, and prevent cancer; but there is little scientific basis for these claims.

Taking dietary supplements such as 5-HTP, kava kava, or valerian in combination with melatonin may increase its sedative side effects. Similarly, taking melatonin in combination with medicines that can cause drowsiness such as benzodiazepines including lorazepam (brand name ativan) or diazepam (valium), pain relievers (codeine or morphine), or alcohol may also increase the sedative side effects of melatonin.

You should avoid melatonin supplements if you take medicines affecting immune function such as prednisone (Orasone), cyclosporine (Sandimmune or Neoral), or azithioprine (Imuran).

Taking melatonin with fluvoxamine (Luvox), nifedipine (Procardia, Adalat), or warfarin (Coumadin) may increase your risk of side effects as well.

Sources:
Integrative Medicine Access. Integrative Medicine Communications, 2000.
Peirce, A. The American Pharmaceutical Association Practical Guide to Natural Medicines. William Morrow & Co., 1999.
The Review of Natural Products. Facts & Comparisons, 2007.
Natural Medicines Comprehensive Database. Pharmacist's Letter, 2000.
Micromedex® Healthcare Series. Thomson Micromedex, 2007.

This answer prepared 12/13/2000.
This information updated 2/7/2007.