Table 1.

Drug withdrawal studies.

Authors	Year	Disease	Treatment	Number of patients	Length of preceding remission	Number of patients allocated to different groups	Study duration	Outcome
Riis et al. [9]	1973	UC	Sulphasalazine	49	≥12 months	Continue on drug: 25, placebo: 24	6 months	No significant difference between the relapse rates (24 versus 29%)
Dissanayake and Truelove [10]	1973	UC	Sulphasalazine	64	≥12 months	Continue on drug: 33, placebo: 31	6 months	Significantly higher relapse rate in the placebo group (>50% versus 12%)
Ardizzone et al. [11]	1999	UC	5-ASA	112	≥12 months	Group A (in remission for 1-2 years): continue on drug: 26, placebo: 35; Group B (in remission for >2 years): continue on drug: 28, placebo: 23	12 months	Group A: no significant difference after 6 months, but significantly higher relapse rates in the placebo group after 12 months (23% versus 49%). Group B: no significant difference at 6 and 12 months.
Hawthorne et al. [12]	1992	UC	Azathioprine	79	≥2 months or chronic stable disease	Remission group: continue on drug: 33, placebo: 34; chronic stable disease group: continue on drug: 7, placebo: 5	12 months	Remission group: significantly higher relapse rate in the placebo group (59% versus 36%); chronic stable disease: azathioprine group: 71% relapsed within 6 months; placebo-treated patients: 40% relapsed
O'Donoghue et al. [13]	1978	CD	Azathioprine	51	≥6 months	Continue on drug: 24, placebo: 27	12 months	Significantly higher relapse rate in the placebo group at 6 months (25 versus 0%) and 12 months (41 versus 5%)
Vilien et al. [14]	2004	CD	Azathioprine	28	≥3 months (≥2 years treated with azathioprine)	Continue on drug: 13, stop drug: 15	12 months	Significantly higher relapse rate in the no azathioprine group at 12 months (53 versus 15%), higher azathioprine dose-subgroup (>1.60 mg/kg/day: 67 versus 11%)
Lémann et al. [15]	2005	CD	Azathioprine	83	≥42 months	Continue on drug: 40, placebo: 43	18 months	Significantly higher relapse rate in the placebo group (20.9 versus 7.5%)