Plasma trazodone concentrations and clinical response in elderly depressed patients: a preliminary study.

Steady-state plasma levels of trazodone were determined by HPLC in 11 elderly depressed patients who underwent a 5-week pharmacological treatment with 150 mg/day trazodone in three oral administrations. Clinical antidepressant response, assessed with three different clinical improvement criteria, was significantly correlated with steady-state plasma trazodone concentrations. Moreover, the steady-state plasma trazodone concentration of 650 ng/ml was identified as the threshold value for a good antidepressant response. No correlation was found between the occurrence of side effects and plasma levels of trazodone.