April 22, 2002: What is the toxicity of melatonin?

Melatonin is currently being administered to children as a potential sleep aid.  Although the drug appears to be relatively safe in therapeutic doses as well as in overdose, there are still many unanswered questions regarding this drug.

Melatonin, the principal substance secreted by the pineal gland, may have a role in the biologic regulation of circadian rhythms, sleep, mood, reproduction, tumor growth, and aging.  Melatonin secretion increases soon after the onset of darkness and peaks in the middle of the night.  The circadian rhythm for the release of melatonin is synchronized with the habitual hours of sleep.  Ingestion of melatonin affects the speed of falling asleep as well as the duration and quality of sleep and has hypnotic effects.  Exogenous melatonin has been shown to be of benefit in emergency physicians working nights. 

Some caution must be exercised in the use of commercially available melatonin.  Remember this product is not regulated by the FDA.  Tryptophan, a metabolic precursor of melatonin, caused more than 1500 cases of eosinophia-myalgia syndrome and 36 deaths.  The culprit was a byproduct of the bacterial synthesis of tryptophan, which came from a unique bacterial strain used by a single manufacturer.  The purity of melatonin in commercial preparations has been evaluated and it is definitely variable. 

(Thanks to the pediatrician asking the question.  It is a very timely topic.)

As always, if there are any questions, call the MTPC.

I am interested in any questions that you would like answered in “Question of the Week.”  Please e-mail me with any suggestions at donna.seger@Vanderbilt.edu


Donna Seger, M.D.

Medical Director

Middle Tennessee Poison Center