Are there differences in the symptoms that respond to a selective serotonin or norepinephrine reuptake inhibitor?

We examined two previously published studies comparing a norepinephrine (NE) selective agent, reboxetine, and a serotonin (5-HT) selective agent, fluoxetine, to determine if these agents have different effects on individual depressive symptoms.

Both studies were 8-week, double-blind, comparison studies of men and women with DSM III-R major depression. Within-group effect sizes for individual symptom change on the Hamilton Depression Rating Scale (HAMD) were determined in the observed case samples and in patients for whom the symptom was relatively severe at baseline. We required that any significant differences in one sample be cross-validated in the second.

Two hundred fifty-three subjects in study I and 168 subjects in study II were randomized to reboxetine or fluoxetine. In both samples, depressed mood, decreased interest, and psychic anxiety had the greatest change. Effect sizes for all HAMD symptoms were similar for the two drugs. No difference between groups in one sample was replicated in the second. Among subjects with severe symptoms, no significant differences were cross-validated.

Reboxetine and fluoxetine appear to have similar effects on depressive symptoms. These data suggest that NE and 5-HT selective antidepressant drugs act through the same final common pathway and challenge the belief that symptom differences are useful for antidepressant selection.