A randomized, within-patient, cross-over, placebo-controlled trial on the efficacy and tolerability of the tricyclic antidepressants chlorimipramine and nortriptyline in central pain

Antidepressant drugs are increasingly used in the management of chronic pain. They are mainly prescribed for cancer-related pain and central pain, e.g. phantom or stump pain, post-herpetic neuropathy. However, no controlled clinical trials have validated their in either pathology. Thus, physicians still do not know whether antidepressants are really effective and which might be best. It is still debated whether the effect of antidepressants in the management of chronic pain is limited to the amelioration of frequently concomitant depression or extends to pain itself. To verify both the analgesic effect of tricyclic antidepressants, and the possible relationship between their antidepressant effect and the relief of central pain, we carried out a randomized, within-patient (cross-over) placebo-controlled study in patients suffering from central pain. The results clearly indicate the better analgesic effect of tricyclic antidepressants over placebo (p < 0.0001). Within the antidepressants tested, chlorimipramine, a blocker of serotonin reuptake, is significantly more effective (p < 0.0001) than nortriptyline, a blocker of noradrenaline reuptake. Finally, the antinociceptive effect is independent of the effects of the two drugs on the symptoms of depression.