Sodium valproate in severe migraine and tension-type headache: an open study of long-term efficacy and correlation with blood levels.

We performed an open prospective study of the prophylactic efficacy of sodium valproate in 56 patients among which 35 migraineurs, 7 chronic tension-type headache patients and 14 patients with combined headaches. We compared the mean number of headache days per month during a one-month-baseline period without prophylactic treatment and during the last month of a 6-month-treatment course. Among secondary parameters, we assessed headache intensity, adverse experiences and we measured valproate blood levels after one and after six months of treatment. Sixty percent of migraineurs had a 75% or more improvement in the number of headache days under sodium valproate, most of the remaining attacks being less severe. There was no significant improvement in chronic tension-type headache patients and only a mild effect in patients with combined headaches, almost exclusively on the migraine component. Thirty percent of patients reported adverse effects of which none was serious: there were 3 drop-outs. We found a moderate, but statistically significant, correlation between efficacy and blood levels of sodium valproate.