This update has provided additional confirmation on the effectiveness of antidepressants for neuropathic pain and has provided new information on another antidepressant - venlafaxine. There is still limited evidence for the role of SSRIs. Whether antidepressants prevent the development of neuropathic pain (pre-emptive use) is still unclear. Both TCAs and venlafaxine have NNTs of approximately three. This means that for approximately every three patients with neuropathic pain who are treated with either of these antidepressants, one will get at least moderate pain relief. There is evidence to suggest that other antidepressants may be effective but numbers of participants are insufficient to calculate robust NNTs. SSRIs are generally better tolerated by patients and more high quality studies are required.
Gabapentin and venlafaxine for the treatment of painful diabetic neuropathy.
To evaluate the safety and efficacy of gabapentin and venlafaxine in the treatment of painful diabetic neuropathy in patients whose pain did not improve with gabapentin monotherapy.
                (1) A randomized, double-blind, placebo-controlled, 8-week clinical trial comparing gabapentin versus placebo to define a patient population whose pain did not improve with monotherapy; (2) a second 8-week trial comparing gabapentin plus venlafaxine with gabapentin plus placebo; (3) a third uncontrolled 8-week trial of patients who did not improve on gabapentin monotherapy and then received venlafaxine in addition to gabapentin.
                (1) Gabapentin-treated patients showed statistically significant improvement in pain reduction as well as improvement in quality of life and mood disturbance when compared with placebo-treated patients; (2) patients who received gabapentin plus venlafaxine showed significant improvement in pain reduction, mood disturbance, and quality of life when compared with patients treated with gabapentin plus placebo; (3) patients who received gabapentin plus venlafaxine showed significant improvement in pain reduction, mood disturbance, and quality of life.
                (1) Gabapentin is efficacious in the treatment of painful diabetic neuropathy; (2) and (3) in patients who do not respond to gabapentin monotherapy, the addition of venlafaxine is also efficacious.