This study is a single center, open label, dose escalation trial to evaluate prolongation effect on QT interval of NPC-15 (melatonin 8mg or 16mg).~The trial compose of 3 periods; During the each period, eligible volunteers wll be administered placebo, NPC-15 4g (melatonin 8mg) and NPC-15 8g(melatonin 16mg) as a sequential manner.
A study to assess the QTc prolongation effect of NPC-15 (melatonin 8mg or 16mg)