Study	Reason for exclusion
Abs 2000	Retrospective
Bouckoms 1992	Retrospective
Chevlen 2000	Substantial proportion of patients had cancer pain
Desai 1997	Fewer than 10 patients remaining for long‐term evaluation
Dobscha 2009	Not a study on opioids
Franco 2002	Retrospective
Fredheim 2006b	No clinical outcomes reported
Gatti 2009	Insufficient duration of treatment (< 6 months)
Griessinger 2005	Substantial proportion of patients with cancer pain
Kalso 2007	Secondary analysis only (no original data)
Kanoff 1994	Retrospective
Krames 1993	Retrospective
Likar 2001	Retrospective
Likar 2006	Substantial proportion of patients had cancer pain
Mariconti 2008	Insufficient duration of treatment (< 6 months)
Milligan 1999	Fewer than 10 participants enrolled
Mironer 1999	Retrospective
Moulin 2005	Retrospective
Pappagallo 1994	Participants do not meet IASP definition of chronic pain (lasting at least 3 months)
Podichetty 2008	Outcomes collected cross‐sectionally, pain reduction requires recall
Quang‐Cantagrel 2000	Retrospective
Raphael 2004	Retrospective
Rauck 2007	Duration of treatment when outcomes were reported not long‐term (< 6 months)
Schulzek 1993	Retrospective
Tutak 1996	Retrospective
Valentino 1998	Retrospective
Willis 1999	Retrospective
Winkelmuller 1996	Retrospective
Worz 1995	Retrospective