In heart failure, months of melatonin did not weaken pumping
In three trials of 3 to 20 mg a day for 8 to 24 weeks, the heart's pumping did not differ clearly from placebo, and no serious harm was reported.
What the study found
Heart-failure patients on melatonin pumped no worse than on placebo
Three trials gave people with heart failure 3 to 20 mg of melatonin a day for 8 to 24 weeks. Ejection fraction, the share of blood pumped per beat, did not differ clearly from placebo, and no serious harm from melatonin was reported. Failing hearts showed no measured decline.
The caveat · Just 201 patients in three trials
The three trials enrolled 201 people in all. The estimate ran from about a 2-point fall to a 6-point rise in ejection fraction, so a small effect either way is not ruled out. Harms were reported inconsistently across the trials. A second review reaching the same result drew on some of the same trials.