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.
Clomipramine vs desipramine vs placebo in the treatment of diabetic neuropathy symptoms. A double-blind cross-over study.
1. The effect of clomipramine and desipramine on diabetic neuropathy symptoms was examined in a double-blind, randomised, placebo controlled, cross-over study for 2 + 2 + 2 weeks. Drug doses were adjusted according to the sparteine phenotype, i.e. extensive metabolisers were treated with 75 mg clomipramine day-1 and 200 mg desipramine day-1 whereas poor metabolisers were treated with 50 mg day-1 of both drugs. Nineteen patients completed the study. 2. Plasma concentration of clomipramine plus desmethylclomipramine was 70-510 nM in extensive metabolisers, vs 590 and 750 nM in two poor metabolisers. Desipramine levels were 130-910 nM, vs 860 and 880 nM. 3. Both clomipramine and desipramine significantly reduced the symptoms of neuropathy as measured by observer- and self rating in comparison with placebo. Clomipramine tended to be more efficacious than desipramine. Patients with a weak or absent response on clomipramine had lower plasma concentrations (clomipramine plus desmethyl-clomipramine less than 200 nM) than patients with a better response. For desipramine a relationship between plasma concentration and effect was not established. 4. Side effect ratings did not differ for clomipramine and desipramine and on both drugs three patients withdrew due to side effects. 5. Compared with earlier results obtained with imipramine dosed on the basis of plasma level monitoring, clomipramine and desipramine on fixed doses appeared less efficacious whereas the side effect profiles were the same. At least for clomipramine, appropriate dose adjustment on the basis of plasma level monitoring may increase the efficacy.