Randomized double-blind comparison of serotonergic (Citalopram) versus noradrenergic (Reboxetine) reuptake inhibitors in outpatients with somatoform, DSM-IV-TR pain disorder

Objectives: Whether the effect of tricyclic antidepressants on Pain Disorder arises from their noradrenergic or serotonergic actions or both remains unclear. We compared the selective serotonin reuptake inhibitor (SSRI) citalopram and the noradrenergic reuptake inhibitor (NARI) reboxetine in outpatients with Pain Disorder. We also distinguished the drugs' analgesic and antidepressant effects. Methods: In this 8-week, randomized double-blind study, 35 patients with a DSM-IV-TR diagnosis of Pain Disorder were randomly assigned to receive either citalopram 40 mg/day (N=17 patients) or reboxetine 8 mg/day (N=18). The Present Pain Intensity (PPI) scale and the Total Pain Rating Index (tPRI) of the McGill Pain Questionnaire were used to measure the effect on pain symptoms. Changes in the Zung Self-Rating Depression Scale (Zung-D) scores were evaluated to monitor a possible antidepressant effect. For all patients who had at least one assessment, an intent-to-treat analysis was performed. Results: No significant differences were found in the demographic variables or clinical characteristics of the two treatment groups. In the citalopram group, PPI and tPRI scores measured at baseline decreased after treatment (tPRI: 41.9 vs. 30.0, p=.004; PPI: 3.5 vs. 2.8, p=.045) whereas in the reboxetine group differences were not statistically significant (tPRI: 35.2 vs. 31.5; PPI: 3.7 vs. 3.1). The Zung-D showed no significant changes between baseline and endpoint assessment in either group. Conclusions: Our study suggests that the SSRI citalopram may have a moderate analgesic effect in patients with Pain Disorder, and that this analgesic activity appears to be not correlated to changes in depressive scores. If confirmed in a larger sample, this evidence suggests that patients who are intolerant or resistant to tricyclic antidepressants, may be treated with SSRIs.