Comparison 2. Azathioprine or 6‐mercaptopurine versus mesalazine or sulfasalazine.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Maintenance of remission	2	166	Risk Ratio (M‐H, Fixed, 95% CI)	1.09 [0.88, 1.34]
1.1 Azathioprine 2‐2.5mg/kg/day	1	38	Risk Ratio (M‐H, Fixed, 95% CI)	1.0 [0.76, 1.32]
1.2 Azathioprine 1.0 mg/kg/day	1	112	Risk Ratio (M‐H, Fixed, 95% CI)	1.10 [0.84, 1.45]
1.3 6‐mercaptopurine 1.5mg/kg	1	16	Risk Ratio (M‐H, Fixed, 95% CI)	2.13 [0.18, 24.48]
2 Adverse events	1	45	Risk Ratio (M‐H, Fixed, 95% CI)	8.77 [0.54, 142.51]
2.1 Azathioprine 2‐2.5mg/kg/day	0	0	Risk Ratio (M‐H, Fixed, 95% CI)	0.0 [0.0, 0.0]
2.2 Azathioprine 1.0 mg/kg/day	0	0	Risk Ratio (M‐H, Fixed, 95% CI)	0.0 [0.0, 0.0]
2.3 6‐Mercaptopurine 50mg/day	1	45	Risk Ratio (M‐H, Fixed, 95% CI)	8.77 [0.54, 142.51]
3 Withdrawals due to adverse events	2	290	Risk Ratio (M‐H, Fixed, 95% CI)	1.86 [0.87, 3.97]
3.1 Azathioprine 2‐2.5mg/kg/day	1	133	Risk Ratio (M‐H, Fixed, 95% CI)	0.94 [0.35, 2.56]
3.2 Azathioprine 1.0mg/kg/day	1	112	Risk Ratio (M‐H, Fixed, 95% CI)	4.30 [0.95, 19.34]
3.3 6‐mercaptopurine 50mg/day	1	45	Risk Ratio (M‐H, Fixed, 95% CI)	4.65 [0.27, 81.01]
4 Serious adverse events	2	235	Risk Ratio (M‐H, Fixed, 95% CI)	9.37 [1.84, 47.72]
4.1 Azathioprine 2‐2.5mg/kg/day	1	78	Risk Ratio (M‐H, Fixed, 95% CI)	19.0 [1.15, 313.35]
4.2 Azathioprine 1mg/kg/day	1	112	Risk Ratio (M‐H, Fixed, 95% CI)	5.36 [0.26, 109.26]
4.3 6‐mercaptopurine 50mg/day	1	45	Risk Ratio (M‐H, Fixed, 95% CI)	4.65 [0.27, 81.01]