Long term efficacy of paroxetine in major depression: A study with plasma levels.

Depressive disorders can be regarded as recurrent and chronic conditions that may reduce the quality of life and work output of patients. Data on the long-term efficacy of paroxetine appear to indicate that it is an effective maintenance treatment. Our aim was to measure paroxetine concentrations in plasma in order to optimize its clinical efficacy and tolerability during long-term treatment. We studied 35 patients aged 23-70 years, suffering from Major Depressive Disorder (recurrent). These patients received 10-50 mg of paroxetine once a day for one year; they were evaluated at baseline, after 2 weeks and then after 1,2,6,9 and 12 months by BPRS, HRS-D and HRS-A rating scales, and at the same time, any side-effects were assessed and samples for paroxetine plasma determination were also collected. Results confirmed the efficacy and tolerability of paroxetine for long-term treatment. We observed a curvilinear relationship between plasma paroxetine levels and improvement on the HRS-D with greater clinical amelioration at plasma levels between 20 and 70 ng/ml.