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vasopressin. Increased breast size and decreased sperm count and motility have been
reported in men.
Given the lack of experimental data concerning melatonin supplementation in children,
Mischoulon and Rosenbaum caution that melatonin treatment in children should be
used only “very conservatively," when the benefits of melatonin treatment clearly
outweigh any possible risks. There are no data concerning use during pregnancy or
breastfeeding.
The safety of high-dose or long-term melatonin use have not been evaluated. Doses
above 50 mg per day may have long-term effects on testosterone or prolactin levels.
Thus, patients on long-term daily melatonin should be monitored for possible adverse
effects.
Mischoulon and Rosenbaum caution that millions of Americans currently consume
melatonin in quantities that elevate their hormone levels “manyfold” over those that
occur normally. The notion that uncontrolled use of melatonin is completely safe rests
on little research and on the common public experience of lack of significant short-
term toxic effects. Long-term clinical and experimental studies are needed to address
this important question, since disruption of the "delicate mechanism" of the circadian
system is, in and of itself, a significant potential side effect.
- CIRCADIAN PATTERNS AND DOSAGE: Over-the-counter melatonin supplements typically
contain 3-5 mg, but Mischoulon and Rosenbaum caution that even a relatively low dose of
0.3 mg per day may induce circadian levels of the hormone in people over 50 years old well
in excess of the normal level. Other potential effects of large doses of melatonin include
lowering of body temperature, reflecting changes in either energy metabolism or
temperature regulation, and unwanted modifications in human reproductive function.
Finally, Mischoulon and Rosenbaum caution that it is important to avoid bright light
exposure during melatonin treatment, since even regular room light can rapidly suppress
melatonin production. In addition, exposure to bright light could produce an adverse effect,
since melatonin has been reported to increase photoreceptor susceptibility.
