Plasma catecholamine levels after fluoxetine treatment in depressive patients

It is known that selective serotonin reuptake inhibitors, widely used as antidepressive drugs, act by inhibiting the cell reuptake of serotonin, but their effect on the catecholaminergic system is not yet completely understood. In this study, we investigated plasma concentrations of norepinephrine, epinephrine and dopamine after acute and chronic administration of fluoxetine in depressive patients. Twelve patients affected by major depression received a single oral dose of fluoxetine in the morning, 5 mg in the first 5 days, 10 mg from the 6th to the 10th day and 20 mg from the 11th to the 40th day. Twelve healthy subjects received a placebo under identical testing procedures. Blood samples were collected at baseline and 7, 10 and 24 h after drug administration on the 1st day of fluoxetine administration at a dose of 5 mg, and on the 1st and the 30th day of fluoxetine administration at a dose of 20 mg (days 11 and 40 of treatment, respectively). We found that plasma norepinephrine, epinephrine and dopamine levels significantly increased after acute and chronic treatment (p < 0.001), reaching the highest concentrations on the last day. No significant changes of these parameters were observed in control patients.