Management of diabetic neuropathy by sodium valproate and glyceryl trinitrate spray: a prospective double-blind randomized placebo-controlled study. Sodium valproate for painful diabetic neuropathy: a randomized double-blind placebo-controlled study. Divalproex sodium in the management of post-herpetic neuralgia: a randomized double-blind placebo-controlled study.
Combination of drugs with different mechanisms of action helps in achieving synergistic analgesic effect in neuropathic pain. Keeping this point in view, the effect and safety aspects of sodium valproate and GTN were assessed alone as well as in combination in this study.
                Prospective double-blind randomized placebo-controlled study.
                Eighty-seven type 2 diabetics with painful neuropathy were enrolled. Four were excluded: three with HbA1c>11 while one withdrew consent. The remaining 83 were given either sodium valproate and GTN spray (group A) or placebo drug and GTN spray (group B) or sodium valproate and placebo spray (group C) or placebo drug and placebo spray (group D). Quantitative assessment of pain was done by McGill pain questionnaire, visual analogue score (VAS) and present pain intensity (PPI) at the beginning of the study and after 3 months along with motor and sensory nerve conduction velocities measurements.
                All the three treatment groups experienced significant improvement in pain score in their drug phase of trial (p<0.001/<0.05) along with some of the electrophysiological parameters. The assessment of the magnitude of therapeutic effect of sodium valproate, GTN and their combination gave numbers needed to treat (NNT) of 7, 5 and 4, respectively.
                Sodium valproate and GTN are well tolerated and provide significant improvement in pain scores as well as in electrophysiological parameters. Various drugs are effective in the management of painful diabetic neuropathy, but none is completely satisfactory. We previously found sodium valproate to be effective and safe in a short-term study.
                To test the effectiveness and safety of sodium valproate in the management of painful diabetic neuropathy over 3 months.
                Randomized double-blind placebo-controlled study.
                Consecutive attending patients with type 2 diabetes mellitus with painful neuropathy were asked to participate in the trial: 48 agreed. Five were excluded: three with HbA(1c) > 11, one with too low a pain level and one who withdrew consent. The remaining 43 were given either drug (group A) or placebo (group B). Each patient was assessed clinically. Quantitative assessment of pain was done by McGill Pain Questionnaire, Visual Analogue Score and Present Pain Intensity, at the beginning of the study, after 1 month and after 3 months. Motor and sensory nerve conduction velocities were measured initially and after 3 months. Liver function tests and other adverse drug-related effects were assessed periodically.
                Of the 43 patients, four dropped out: one in group A and three in group B. There was significant improvement in pain score in group A, compared to group B, at 3 months (p < 0.001). Changes in electrophysiological data were not significant. The drug was well-tolerated by all patients, except one, who had raised serum AST and ALT levels after 1 month of treatment, and whose treatment was discontinued.
                Sodium valproate is well-tolerated, and provides significant subjective improvement in painful diabetic neuropathy. Post-herpetic neuralgia is difficult to treat. Divalproex sodium (valproic acid and sodium valproate in molar ratio 1:1) has been used successfully in the management of various painful neuropathies.
                To study the effectiveness and safety of divalproex sodium in the management of post-herpetic neuralgia.
                Randomized double-blind placebo-controlled trial.
                We enrolled 48 consecutively attending out-patients with post-herpetic neuralgia, out of whom three were excluded (two had insufficient pain, one withdrew consent). Quantification of pain was by Short Form-McGill pain questionnaire (SF-MPQ), visual analogue scale (VAS), present pain intensity score (PPI) and 11 point Likert scale (11 PLS) at the beginning of the study, after 2 weeks, 4 weeks and at the end of the study (8 weeks). We also assessed patients' global impression of change by questionnaire at the end of the study.
                After 8 weeks treatment with 1000 mg/day divalproex sodium, there was significant reduction in pain: SF-MPQ, 20.47 +/- 2.29 to 11.90 +/- 6.52 (p < 0.0001); PPI 4.0 +/- 0.52 to 1.95 +/- 1.29 (p < 0.0001); VAS 70.17 +/- 9.21 to 31.27 +/- 29.74 (p < 0.0001) and 11 PLS 6.97 +/- 0.73 to 3.63 +/- 2.34 (p < 0.0001) in comparison to placebo (means +/- SEM). The 'global impression of change' questionnaire showed much or moderate improvement in pain in 58.2% of patients receiving divalproex vs. 14.8% of those receiving placebo. The drug was well tolerated by all patients, except one who developed severe vertigo after 10 days of treatment.
                Divalproex sodium provides significant pain relief in patients of post-herpetic neuralgia, with very little incidence of adverse reactions. These data provide a basis for longer trials in a larger group of patients.
These three studies no more than hint that sodium valproate may reduce pain in diabetic neuropathy, and divalproex sodium in post-herpetic neuralgia, but the use of 'completer' analysis may overestimate efficacy, and there were too few data for pooled analysis of efficacy or harm, or to have confidence in the results of the individual studies. There is insufficient evidence to support the use of valproic acid or sodium valproate as a first-line treatment for neuropathic pain. There is more robust evidence of greater efficacy for a small number of other drugs.