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.
Venlafaxine extended release in the treatment of painful diabetic neuropathy: a double-blind, placebo-controlled study.
To evaluate the efficacy and safety of 6 weeks of venlafaxine extended-release (ER) (75 mg and 150-225 mg) treatment in patients with painful diabetic neuropathy. This multicenter, double-blind, randomized, placebo-controlled study included 244 adult outpatients with metabolically stable type 1 or 2 diabetes with painful diabetic neuropathy. Primary efficacy measures were scores on the daily 100 mm Visual Analog Pain Intensity (VAS-PI) and Pain Relief (VAS-PR) scales. Secondary efficacy measures included the Clinical Global Impressions-Severity of Illness and the Clinical Global Impressions-Improvement, Patient Global Rating of Pain Relief, and percentage of patients achieving 50% reduction in pain intensity. Baseline pain intensity was 68.7 mm (moderately severe). At week 6, the percentage reduction from baseline in VAS-PI was 27% (placebo), 32% (75 mg), and 50% (150-225 mg; P < 0.001 vs placebo). Mean VAS-PR scores in the 150-225 mg group were significantly greater than placebo at week 6 (44 vs 60 mm; P < 0.001). The number needed to treat (NNT) for 50% pain intensity reduction with venlafaxine ER 150-225 mg was 4.5 at week 6. Nausea and somnolence were the most common treatment-emergent adverse events. Seven patients on venlafaxine had clinically important ECG changes during treatment. Venlafaxine ER appears effective and safe in relieving pain associated with diabetic neuropathy. NNT values for higher dose venlafaxine ER are comparable to those of tricyclic antidepressants and the anticonvulsant gabapentin.