Send to

Choose Destination
See comment in PubMed Commons below
Clin Pharmacol Ther. 2001 Jul;70(1):10-6.

Orally given melatonin may serve as a probe drug for cytochrome P450 1A2 activity in vivo: a pilot study.

Author information

  • 1Department of Medical Laboratory Sciences and Technology, Division of Clinical Pharmacology, Karolinska Institutet, Huddinge University Hospital, Sweden.



Melatonin is a hormone that is metabolized by cytochrome P450 (CYP) 1A2 to its main primary metabolite 6-hydroxymelatonin. We therefore evaluated the utility of oral melatonin as a marker of hepatic CYP1A2 activity.


Twenty-five milligrams of melatonin was given at 9:30 am to 12 healthy Swedish volunteers, who had previously been phenotyped for CYP1A2 with caffeine. Melatonin and conjugated 6-hydroxymelatonin were analyzed by liquid chromatography-mass spectrometry in blood samples taken between 0.5 and 6.5 hours after drug intake. Serum concentrations of melatonin and conjugated 6-hydroxymelatonin, or their ratio at different time points, and the apparent melatonin clearance were tested for correlation with caffeine clearance.


We found a significant correlation between apparent clearance of melatonin and caffeine clearance with a Spearman rank correlation coefficient (Rs) of 0.75 (P =.005). The melatonin concentration 1.5 hours after administration also closely correlated with the caffeine clearance (Rs = -0.62; P =.03). Inclusion of conjugated 6-hydroxymelatonin gave no closer correlations.


Melatonin might be developed as an alternative to caffeine as a probe drug for CYP1A2 phenotyping.

[PubMed - indexed for MEDLINE]
PubMed Commons home

PubMed Commons

How to join PubMed Commons

    Supplemental Content

    Full text links

    Icon for Wiley
    Loading ...
    Write to the Help Desk