Trazodone treatment increases plasma prolactin concentrations in depressed patients

m-Chlorophenylpiperazine (m-CPP), which is a metabolite of trazodone, is a serotonin agonist. To examine for the possibility that m-CPP is involved in biochemical effects during treatment with the parent compound, prolactin response to trazodone treatment (150 mg at bedtime for 3 weeks) was studied in 12 depressed patients. The means ± S.D. of plasma prolactin concentrations before treatment, 12 h. and 1,2 and 3 weeks after initiation of treatment were 9.1 ± 5.6, 14.7 ± 9.1, 15.3 ± 8.5, 13.2 ± 7.0 and 13.0 ± 7.0 ng/ml, respectively. The mean prolactin concentrations at 12 h(p < 0.01), 1 week(p < 0.001) and 2 weeks (p < 0.05) were significantly higher than that before treatment. The present study thus shows that trazodone treatment increases prolactin concentrations, suggesting that m-CPP is involved in biochemical effects during treatment with the parent compound.