The half-life of melatonin elimination from rat plasma.

Tritiated or unlabeled melatonin was infused intra-arterially into unanesthetized male Sprague-Dawley rats. Blood samples were collected from the jugular vein over the next two hours and the melatonin concentrations determined in the plasma by liquid scintillation counting or by RIA. Data from the tritiated melatonin experiments gave a half-life of 23 min, and data from the RIA experiments gave a half-life of 17 min.