The absolute bioavailability of oral melatonin.
The absolute bioavailability of oral melatonin tablets was studied in 12 normal healthy volunteers. Subjects were administered, in a randomized crossover fashion, melatonin 2 mg intravenously and 2 and 4 mg orally. Blood was sampled over approximately eight (estimated) half-lives. Both the 2 and the 4 mg oral dosages showed an absolute bioavailability of approximately 15%. No difference in serum half-life was seen in any of the study phases. Oral melatonin tablets in dosages of 2 and 4 mg show poor absolute bioavailability, either due to poor oral absorption, large first-pass metabolism, or a combination of both. Further studies examining larger doses, in an attempt to saturate first-pass metabolism if it occurs, may be warranted.
DeMuro
R L
RL
Department of Medicine, Bassett Healthcare, Cooperstown, New York 13326, USA.
Nafziger
A N
AN
Blask
D E
DE
Menhinick
A M
AM
Bertino
J S
JS
D000284:Administration, Oral; D000328:Adult; D000975:Antioxidants / Q000008:administration & dosage / Q000493:pharmacokinetics*; D001682:Biological Availability; D005260:Female; D006801:Humans; D008297:Male; D008550:Melatonin / Q000008:administration & dosage / Q000493:pharmacokinetics*
D000975:Antioxidants; D008550:Melatonin