Efficacy of Valproate in Peripheral Neuropathic Pain

• Intensity of pain on a visual analog scale [ Time Frame: after 4 weeks of treatment ]
  

• intensity of mechanic allodynia
  
• intensity of dynamic allodynia
  
• use of analgesics (rescue medication)
  
• thermal sensitive and nociceptive thresholds, RIII reflex
  

Background. Neuropathic peripheral pain is often refractory to usual analgesics. Some anticonvulsant drugs may be effective, but often partially only, and not always well tolerated. Valproate is a well-known anticonvulsant drug, with moderate possible adverse events and for which an intravenous form is available.

Aim. The principal aim is to assess the efficacy and safety of sodium Valproate in peripheral neuropathic pain. Secondary aims are to asses the effect of IV and oral treatment on neurophysiologic measures.

Design. Randomized, double-blind vs. placebo, parallel groups, monocentric clinical trial.

Treatments. Experimental arm: Intravenous eight-hour sodium Valproate infusion, followed by a four-week oral route sodium Valproate treatment. Control arm: Intravenous eight-hour placebo infusion, followed by a four-week oral route placebo treatment. Rescue medications are allowed in both groups.

Eligibility criteria. Peripheral neuropathic pain with pain intensity of at least 40 mm on a visual analog scale.

Outcomes. Primary outcome is the intensity of pain on a visual analog scale after 4 weeks of treatment. Secondary outcomes: intensity of pain after IV treatment; neurophysiologic measures (thermal thresholds, RIII reflex); association of response to IV treatment with oral treatment efficacy.