Chronic pain is both difficult for patients to tolerate and for clinicians to treat effectively. It differs from other types of
pain in etiology and impact, which in turn affects the duration and modalities of treatment options. Forty years of research have confirmed the efficacy of
antidepressant agents in the management of chronic
pain, yet these agents are used inadequately. A significant amount of evidence supports the use of the traditional
tricyclic antidepressants (TCAs) in the management of chronic
pain, but because of their acute synaptic effects on multiple, nontherapeutic receptor systems, they are associated with numerous undesirable side effects. The newer
selective serotonin reuptake inhibitors (
SSRIs) have, comparatively, only
serotonin-receptor-mediated side effects. These agents have not been thoroughly studied in the treatment of
chronic pain. Moreover, because
SSRIs impact reuptake of only one monoamine system, it is plausible that they may be less efficacious than the TCAs in treating
chronic pain.
Venlafaxine, the first agent in the new class of
serotonin (5-HT)-norepinephrine (NE) reuptake inhibitors, is unique because it inhibits reuptake of both
5-HT and NE (and to a lesser extent
dopamine), as do some of the TCAs; however, it accomplishes this without affecting other nontherapeutic receptors.
Venlafaxine is at least as effective as the TCAs, but is more tolerable, because it lacks the receptor-mediated side effects common to the TCAs. The unique characteristics of
venlafaxine, including minimal
cytochrome P-450 drug interaction, may make it a particularly useful
antidepressant in the adjunctive treatment of
chronic pain.