Serotonin and Norepinephrine Reuptake Inhibitors

Major depressive disorder is one of the most common mental disorders in children and adolescents. However, whether to use pharmacological interventions in this population and which drug should be preferred are still matters of controversy. Consequently, we aimed to compare and rank antidepressants and placebo for major depressive disorder in young people.

Recent reports describe discontinuation-emergent adverse events upon cessation of selective serotonin reuptake inhibitors including dizziness, insomnia, nervousness, nausea, and agitation. We hypothesized that interruption of fluoxetine treatment would be associated with fewer discontinuation-emergent adverse events than interruption of sertraline or paroxetine treatment, based on fluoxetine's longer half-life. In this 4-week study, 242 patients with remitted depression receiving maintenance therapy with open-label fluoxetine, sertraline, or paroxetine for 4-24 months had their maintenance therapy interrupted with double-blind placebo substitution for 5-8 days. The Symptom Questionnaire (SQ), the Discontinuation-Emergent Signs and Symptoms checklist, the 28-item Hamilton Depression Rating Scale, and the Montgomery-Asberg Depression Rating Scale were used to assess somatic distress and stability of antidepressant response. Two hundred twenty patients (91%) completed the study. Following interruption of therapy, fluoxetine-treated patients experienced fewer discontinuation-emergent events than either sertraline-treated or paroxetine-treated patients (p < .001). The mean SQ somatic symptom scale score in fluoxetine-treated patients was significantly lower than that in sertraline-treated and paroxetine-treated patients (p < .001). Fluoxetine-treated patients also experienced less reemergence of depressive symptoms than sertraline-treated or paroxetine-treated patients (p < .001). Abrupt interruption of antidepressant therapy for 5-8 days was associated with the emergence of new somatic and psychological symptoms in patients treated with paroxetine and to a lesser degree sertraline, with few symptoms seen with fluoxetine.

The blockade of serotonin (5-HT) and norepinephrine (NE) transporters in vitro and in vivo by the dual 5-HT/NE reuptake inhibitors duloxetine and venlafaxine was compared. Duloxetine inhibited binding to the human NE and 5-HT transporters with K(i) values of 7.5 and 0.8 nM, respectively, and with a K(i) ratio of 9. Venlafaxine inhibited binding to the human NE and 5-HT transporters with K(i) values of 2480 and 82 nM, respectively, and with a K(i) ratio of 30. Duloxetine inhibited ex vivo binding to rat 5-HT transporters and NE transporters with ED(50) values of 0.03 and 0.7 mg/kg, respectively, whereas venlafaxine had ED(50) values of 2 and 54 mg/kg, respectively. The depletion of rat brain 5-HT by p-chloramphetamine and depletion of rat hypothalamic NE by 6-hydroxydopamine was blocked by duloxetine with ED(50) values of 2.3 and 12 mg/kg, respectively. Venlafaxine had ED(50) values of 5.9 and 94 mg/kg for blocking p-chloramphetamine- and 6-hydroxydopamine-induced monoamine depletion, respectively. Thus, duloxetine more potently blocks 5-HT and NE transporters in vitro and in vivo than venlafaxine.