Comparison 1. Divalproex sodium versus placebo.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 ORs for responders (patients with ≥ 50% reduction in headache frequency)	4	574	Odds Ratio (M‐H, Random, 95% CI)	3.34 [1.46, 7.67]
1.1 Divalproex sodium titrated to 1500 mg/day	1	105	Odds Ratio (M‐H, Random, 95% CI)	5.68 [1.98, 16.34]
1.2 Divalproex sodium titrated to maintain plasma concentration of 70 to 120 mg/L (mean 1087 mg/day)	1	64	Odds Ratio (M‐H, Random, 95% CI)	8.27 [2.62, 26.10]
1.3 Divalproex sodium titrated to 500 mg or 1000 mg/day, as tolerated	1	234	Odds Ratio (M‐H, Random, 95% CI)	1.35 [0.76, 2.40]
1.4 Divalproex sodium 500 mg, 1000 mg, or 1500 mg/day (combined results)	1	171	Odds Ratio (M‐H, Random, 95% CI)	2.90 [1.29, 6.56]
2 RRs for responders (patients with ≥ 50% reduction in headache frequency)	4	574	Risk Ratio (M‐H, Random, 95% CI)	2.18 [1.28, 3.72]
2.1 Divalproex sodium titrated to 1500 mg/day	1	105	Risk Ratio (M‐H, Random, 95% CI)	3.44 [1.47, 8.06]
2.2 Divalproex sodium titrated to maintain plasma concentration of 70 to 120 mg/L (mean 1087 mg/day)	1	64	Risk Ratio (M‐H, Random, 95% CI)	3.5 [1.63, 7.51]
2.3 Divalproex sodium titrated to 500 mg or 1000 mg/day, as tolerated	1	234	Risk Ratio (M‐H, Random, 95% CI)	1.24 [0.81, 1.90]
2.4 Divalproex sodium 500 mg, 1000 mg, or 1500 mg/day (combined results)	1	171	Risk Ratio (M‐H, Random, 95% CI)	2.06 [1.12, 3.80]