The Absolute Bioavailability of Oral Melatonin

Authors

  • Dr. Rob L. DeMuro MD,

    1. Department of Medicine, Bassett Healthcare, Cooperstown, New York.
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  • Dr. Anne N. Nafziger MD, MHS,

    1. Department of Medicine, Bassett Healthcare, Cooperstown, New York.
    2. Clinical Pharmacology Research Center, Bassett Healthcare, Cooperstown, New York.
    3. Research Institute, Bassett Healthcare, Cooperstown, New York.
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  • Dr. David E. Blask MD, PhD,

    1. Research Institute, Bassett Healthcare, Cooperstown, New York.
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  • Ms. Anne M. Menhinick BSN, RN,

    1. Clinical Pharmacology Research Center, Bassett Healthcare, Cooperstown, New York.
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  • Dr. Joseph S. Bertino Jr. PharmD

    Corresponding author
    1. Department of Medicine, Bassett Healthcare, Cooperstown, New York.
    2. Clinical Pharmacology Research Center, Bassett Healthcare, Cooperstown, New York.
    3. Research Institute, Bassett Healthcare, Cooperstown, New York.
    4. Department of Pharmacy Services, Bassett Healthcare, Cooperstown, New York.
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Director, Clinical Pharmacy Services, Codirector Clinical Pharmacology Research Center, Bassett Healthcare, One Atwell Road, Cooperstown, NY 13326.

Abstract

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.

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