Effects of Paroxetine and Milnacipran on Pain Disorder

Abstract

The outcomes of treatment for pain disorder are generally disappointing: symptoms are poorly controlled, they are seldom managed by experts, and they are often long standing. The aim of the present study was to compare the therapeutic effectiveness of paroxetine and milnacipran for outpatients with pain disorder. The study was performed on 43 consecutive outpatients with pain disorder diagnosed according to DSM-IV-TR criteria. Patients were treated with either antidepressant for 8 weeks. Pain was self-assessed using the Short-Form McGill Pain Questionnaire (SF-MPQ), the total Pain Rating Index (t-PRI), Present Pain Intensity (PPI), and visual analogue scale (VAS). In addition, pain was evaluated objectively using Pain Vision (a machine devised by NIPRO for semiquantitative measurements). Possible depressive symptoms were rated on the Hamilton Depression Scale (HAM-D) and the Zung Self-rating Depression Scale (SDS). Although VAS scores decreased significantly over the course of the 8-week trial in both the paroxetine- and milnacipran-treated groups (from 6.6 ± 2.3 to 4.8 ± 3.0 [P = 0.01] and from 7.5 ± 2.4 to 5.4 ± 3.3 [P = 0.03], respectively), the t-PRI decreased only in the paroxetine group (from 13.9 ± 10.1 to 7.6 ± 7.5; P = 0.01). The Pain Vision indicated a tendency for decreased pain in both groups, with no significant differences between them. There were no significant changes in the SDS in either group, but the HAM-D decreased significantly in the milnacipran-treated group (from 7.8 ± 4.0 to 6.7 ± 3.9; P = 0.04). The results of the present study suggest that both paroxetine (a selective serotonin re-uptake inhibitor) and milnacipran (a selective serotonin–noradrenaline re-uptake inhibitor) may decrease pain in individuals with pain disorder.