Comparison 1. Azathioprine or 6‐mercaptopurine versus placebo.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Clinical relapse at 12 to 36 months (subgroup by drug type)	3	408	Risk Ratio (M‐H, Random, 95% CI)	0.79 [0.67, 0.92]
1.1 Azathioprine	1	81	Risk Ratio (M‐H, Random, 95% CI)	0.59 [0.33, 1.08]
1.2 6‐mercaptopurine	2	327	Risk Ratio (M‐H, Random, 95% CI)	0.80 [0.68, 0.94]
2 Clinical relapse (subgroup by length of follow‐up)	3	408	Risk Ratio (M‐H, Random, 95% CI)	0.79 [0.67, 0.92]
2.1 12 months or less	1	81	Risk Ratio (M‐H, Random, 95% CI)	0.59 [0.33, 1.08]
2.2 Over 12 months	2	327	Risk Ratio (M‐H, Random, 95% CI)	0.80 [0.68, 0.94]
3 Endoscopic relapse at 12 to 36 months (subgroup by drug type)	2	321	Risk Ratio (M‐H, Random, 95% CI)	0.85 [0.64, 1.13]
3.1 Azathioprine	1	81	Risk Ratio (M‐H, Random, 95% CI)	0.70 [0.51, 0.97]
3.2 6‐mercaptopurine	1	240	Risk Ratio (M‐H, Random, 95% CI)	0.95 [0.81, 1.11]
4 Endoscopic relapse (subgroup by length of follow‐up)	2	321	Risk Ratio (M‐H, Random, 95% CI)	0.85 [0.64, 1.13]
4.1 12 months or less	1	81	Risk Ratio (M‐H, Random, 95% CI)	0.70 [0.51, 0.97]
4.2 Over 12 months	1	240	Risk Ratio (M‐H, Random, 95% CI)	0.95 [0.81, 1.11]
5 Adverse events at 12 to 24 months (subgroup by drug type)	2	168	Risk Ratio (M‐H, Random, 95% CI)	1.36 [0.57, 3.27]
5.1 Azathioprine	1	81	Risk Ratio (M‐H, Random, 95% CI)	0.77 [0.18, 3.22]
5.2 6‐mercaptopurine	1	87	Risk Ratio (M‐H, Random, 95% CI)	1.91 [0.64, 5.75]
6 Adverse events (subgroup by length of follow‐up)	2	168	Risk Ratio (M‐H, Random, 95% CI)	1.36 [0.57, 3.27]
6.1 12 months or less	1	81	Risk Ratio (M‐H, Random, 95% CI)	0.77 [0.18, 3.22]
6.2 Over 12 months	1	87	Risk Ratio (M‐H, Random, 95% CI)	1.91 [0.64, 5.75]
7 Serious adverse events at 24 to 36 months	2	327	Risk Ratio (M‐H, Random, 95% CI)	1.78 [0.39, 8.18]
8 Withdrawal due to adverse events at 12 to 36 months (subgroup by drug type)	3	408	Risk Ratio (M‐H, Random, 95% CI)	0.90 [0.63, 1.29]
8.1 Azathioprine	1	81	Risk Ratio (M‐H, Random, 95% CI)	0.77 [0.18, 3.22]
8.2 6‐mercaptopurine	2	327	Risk Ratio (M‐H, Random, 95% CI)	1.07 [0.50, 2.27]
9 Withdrawal due to adverse events (subgroup by length of follow‐up)	3	408	Risk Ratio (M‐H, Random, 95% CI)	0.90 [0.63, 1.29]
9.1 12 months or less	1	81	Risk Ratio (M‐H, Random, 95% CI)	0.77 [0.18, 3.22]
9.2 Over 12 months	2	327	Risk Ratio (M‐H, Random, 95% CI)	1.07 [0.50, 2.27]