Effectiveness and safety of an extended‐release tablet of sodium valproate for the prophylactic treatment of migraine: Postmarketing surveillance in Japan

BACKGROUND Sodium valproate is a standard drug for first-line prophylactic treatment of migraine. However, little information is available of its use in Japanese patients. AIM To evaluate the effectiveness and safety of an extended-release tablet of sodium valproate in the prophylactic treatment for Japanese patients with migraine by postmarketing surveillance. METHODS This was a prospective, multicenter and non-interventional observation study in routine clinical practice. A total of 1222 patients with migraine of all age groups (aged <10 to ≤80 years) and both sexes (17.3% men and 82.7% women) from 169 sites were enrolled. RESULTS Migraine frequency during a 4-week period was reduced from 10.2 ± 6.0 days in 1040 patients to 5.0 ± 4.6 days in 944 patients (P < 0.001): 70.8% of patients experienced remission of migraine by ≥30%, 59.0% by ≥50% and 11.8% by ≥100%. Multivariate analysis and stratification sampling showed that this sodium valproate tablet was the most effective in patients with more migraine days, and complete remission was observed in 29% of patients whose migraine days were less than 3 days per 4 weeks at baseline. The extended-release tablet of sodium valproate reduced migraine intensity and duration of migraine attacks. The incidence of adverse drug reactions was 6.3% (67/1070 patients) and well tolerated. However, four pregnancies were discovered in this survey. CONCLUSIONS This first large observation study in Japan suggests that an extended-release tablet of sodium valproate is effective and safe for the prophylactic treatment of patients with migraine in routine clinical practice.