Sodium valproate in migraine without aura and medication overuse headache: a randomized controlled trial.

OBJECTIVE: To assess the efficacy, safety and tolerability of sodium valproate (800mg/die) compared with placebo in medication-overuse headache patients with a history of migraine without aura. METHODS: This is a multicenter, randomized, double-blind, placebo-controlled study enrolled medication-overuse headache patients for a 3-month treatment period with sodium valproate (800mg/day) or placebo after a 6 day outpatient detoxification regimen, followed by a 3-month follow-up. Primary outcome was defined by the proportion of patients achieving ≥50% reduction in the number of days with headache per month (responders) from the baseline to the last 4 weeks of the 3-month treatment. Multivariate logistic regression models were used on the primary endpoint, adjusting for age, sex, disease duration, comorbidity and surgery. The last-observation-carried-forward method was used to adjust for missing values. RESULTS: Nine sites enrolled 130 patients and, after a 6-day detoxification phase, randomized 88 eligible patients. The 3-month responder rate was higher in the sodium valproate (45.0%) than in the placebo arm (23.8%) with an absolute difference of about 20% (p=0.0431). Sodium valproate had safety and tolerability profiles comparable to placebo. CONCLUSIONS: The present study supports the efficacy and safety of sodium valproate in the treatment of medication overuse headache with history of migraine after detoxification.