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.