Table 4.

The influence of the duration of remission or previous therapy on the outcome after drug withdrawal.

Author	Year	Disease	Drug	Length of previous remission in the different groups	Length of previous therapy with the drug in the different groups	Better outcome at withdrawal after longer remission/therapy
Riis et al. [9]	1973	UC	Sulphasalazine	12–24 months versus >24 months		No
Dissanayake and Truelove [10]	1973	UC	Sulphasalazine	1–3 years versus >3 years		No
Ardizzone et al. [11]	1999	UC	5-ASA	1-2 years versus >2 years		Yes
Hawthorne et al. [12]	1992	UC	Azathioprine	Continuous analysis		Yes; p = 0.1
Fraser et al. [26]	2002	UC	Azathioprine		<2 years versus 2–4 years vs. >4 years	No
Cassinotti et al. [27]	2009	UC	Azathioprine		3–6 months versus 48 months	Yes
O'Donoghue et al. [13]	1978	CD	Azathioprine	<1 years versus 1-2 years versus >2 years	<1 years versus 1-2 years versus >2 years	No
Bouhnik et al. [16]	1996	CD	Azathioprine	6 months–4 years versus >4 years		Yes
Kim et al. [28]	1999	CD	6-Mercaptopurine		<1 year versus 1-2 years versus 2-3 years versus >3 years	No
Holtmann et al. [29]	2006	CD	Azathioprine/6-mercaptopurine		<3 years versus 3-4 years versus >4 years	No
Treton et al. [18]	2009	CD	Azathioprine		Median 62 months versus 80 months	No