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, fluvoxamine (100 mg at 16.00 h), markedly increased nocturnal plasma melatonin concentrations, with high levels extending into the morning hours. 2 Acute administration of the noradrenaline uptake inhibitor, desipramine (DMI) (100 mg at 16.00 h), increased evening plasma melatonin concentrations. 3 Both drug treatments increased the duration of melatonin secretion, fluvoxamine significantly delaying the offset time and DMI significantly advancing the onset time. 4 The stimulatory effect of DMI on plasma melatonin was mirrored by increased urinary 6-sulphatoxymelatonin (aMT6s) excretion. 5 On the contrary, there was no correlation between plasma melatonin and urinary aMT6s concentrations following fluvoxamine treatment, suggesting that fluvoxamine may inhibit the metabolism of melatonin. 6 Treatment with DMI increased plasma cortisol concentrations in the evening and early morning, treatment with fluvoxamine increased plasma cortisol at 03.00 h, 10.00 h and 11.00 h. 7 The drug treatments affected different aspects of the nocturnal plasma melatonin profile suggesting that the amplitude of the melatonin rhythm may depend upon serotonin availability and/or melatonin metabolism whilst the onset of melatonin production depends upon noradrenaline availability.