Differential effects of fluvoxamine and other antidepressants on the biotransformation of melatonin.
Level 5 - mechanism / opinion, no new human data
In vitro laboratory study using human liver microsomes and recombinant enzymes
PubMed 11270913 · doi:10.1097/00004714-200104000-00008
What was done
The authors investigated the biotransformation pathways of melatonin and the inhibitory effects of various antidepressants in vitro using human liver microsomes and recombinant human CYP isoenzymes. Fluvoxamine was evaluated alongside fluoxetine, paroxetine, citalopram, imipramine, and desipramine at concentrations of 2 and 20 µM.
What was found
Melatonin was metabolized almost exclusively by CYP1A2 to 6-hydroxymelatonin and N-acetylserotonin, with minimal contribution from CYP2C19. Fluvoxamine potently inhibited both reactions, with a Ki of 0.02 µM for 6-hydroxymelatonin formation and 0.05 µM for N-acetylserotonin formation. Among other tested antidepressants, only paroxetine showed inhibition, and only at a supratherapeutic concentration of 20 µM, far below the potency of fluvoxamine.
Why it matters
These findings identify the specific enzymatic mechanism (potent CYP1A2 inhibition) explaining why fluvoxamine selectively elevates endogenous melatonin levels compared to other antidepressants.
Limits
The study is entirely in vitro using liver microsomes and recombinant enzymes, not an in vivo clinical trial. The abstract does not specify the number of human liver donors used to prepare the microsomes.
Cited by
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