Studies	Attacks treated	Treatment (%)	Placebo (%)	Relative risk (95% CI)	NNT (95% CI)	P for difference
Effect of size
Pain-free at 2 hours (in studies containing ≥ 50 participants in each treatment arm)	7	1976	58	16	3.6 (3.0 to 4.2)	2.4 (2.2 to 2.7)	z =3.195 P = 0.001
Pain-free at 2 hours (in studies containing 1 or more treatment arm with <50 participants)	6	546	65	11	5.3 (3.7 to 7.6)	1.9 (1.6 to 2.1)
Pain-free at 1 hour (in studies containing ≥ 50 participants in each treatment arm)	9	2985	43	7	5.5 (4.5 to 6.9)	2.9 (2.7 to 3.1)	z =2.210 P = 0.027
Pain-free at 1 hour (in studies containing 1 or more treatment arm with < 50 participants)	7	607	34	6	5.6 (3.4 to 9.3)	3.6 (3.0 to 4.5)
Headache relief at 1 hour (in studies containing ≥ 50 participants in each treatment arm)	12	4040	71	26	2.7 (2.5 to 3.0)	2.2 (2.1 to 2.4)	z =0.145 P = 0.881
Headache relief at 1 hour (in studies containing 1 or more treatment arm with < 50 participants)	12	1137	73	27	2.7 (2.3 to 3.1)	2.2 (2.0 to 2.5)
Headache relief at 2 hours (in studies containing ≥ 50 participants in each treatment arm)	8	2192	78	31	2.5 (2.2 to 2.7)	2.1 (2.0 to 2.3)	z= 1.806 P = 0.070
Headache relief at 2 hours (in studies containing 1 or more treatment arm with < 50 participants)	6	546	84	30	2.7 (2.2 to 3.4)	1.9 (1.6 to 2.1)
Effect of missing data
Pain-free at 1 hour (in studies with no missing data)	14	3208	41	8	5.0 (4.1 to 6.1)	3.0 (2.8 to 3.3)	z =0.908 P = 0.363
Pain-free at 1 hour (in studies with missing data)	2	384	38	1	36 (8.9 to 140)	2.7 (2.3 to 3.3)
Headache relief at 1 hour (in studies with no missing data)	22	4793	71	28	2.6 (2.4 to 2.8)	2.3 (2.2 to 2.5)	z = 4.068 P < 0.00006
Headache relief at 1 hour (in studies with missing data)	2	384	67	7	9.6 (5.7 to 16)	1.7 (1.5 to 1.9)
Headache relief at 2 hours (in studies with no missing data)	12	2354	80	34	2.3 (2.1 to 2.5)	2.2 (2.1 to 2.4)	z = 4.520 P < 0.00006
Headache relief at 2 hours (in studies with missing data)	2	384	74	10	7.4 (4.8 to 11)	1.6 (1.4 to 1.8)