COMPARISON OF THE EFFECTS OF ACUTE FLUVOXAMINE AND DESIPRAMINE ADMINISTRATION ON MELATONIN AND CORTISOL PRODUCTION IN HUMANS

1 Acute administration of the specific serotonin uptake inhibitor, flu voxamine (100 mg at 16.00 h), markedly increased nocturnal plasma mela tonin concentrations, with high levels extending into the morning hour s. 2 Acute administration of the noradrenaline uptake inhibitor, desip ramine (DMI) (100 mg at 16.00 h), increased evening plasma melatonin c oncentrations. 3 Both drug treatments increased the duration of melato nin secretion, fluvoxamine significantly delaying the offset time and DMI significantly advancing the onset time. 4 The stimulatory effect o f DMI on plasma melatonin was mirrored by increased urinary 6-sulphato xymelatonin (aMT6s) excretion. 5 On the contrary, there was no correla tion between plasma melatonin and urinary aMT6s concentrations followi ng fluvoxamine treatment, suggesting that fluvoxamine may inhibit the metabolism of melatonin. 6 Treatment with DMI increased plasma cortiso l concentrations in the evening and early morning, treatment with fluv oxamine increased plasma cortisol at 03.00 h, 10.00 h and 11.00 h. 7 T he drug treatments affected different aspects of the nocturnal plasma melatonin profile suggesting that the amplitude of the melatonin rhyth m may depend upon serotonin availability and/or melatonin metabolism w hilst the onset of melatonin production depends upon noradrenaline ava ilability.