| Level I | Good quality evidence |
Systematic review of RCTs with consistent findings High quality individual RCT |
| Level II |
Limited quality patient orientated evidence |
Systematic review of lower quality studies or studies with inconsistent findings Low quality clinical trial Cohort studies Case-control studies |
| Level III | Other |
Consensus guidelines, extrapolations from bench research, usual practice, opinion, disease-oriented evidence (intermediate or physiologic outcomes only), or case series |
[61] Tramadol, oral: Chattopadhyay S, Singh OP, Bhattacharyya A, Sen S, Roy P, Debnath S. Tramadol versus clonidine in management of heroin withdrawl. Asian J Psychiatr. 2010 Dec;3(4):237-9. http://www.ncbi.nlm.nih.gov/pubmed/23050896
Tramadol, oral: Lofwall MR, Babalonis S, Nuzzo PA, Siegel A, Campbell C, Walsh SL. Efficacy of extended-release tramadol for treatment of prescription opioid withdrawal: a two-phase randomized controlled trial. Drug Alcohol Depend. 2013 Nov 1;133(1):188-97. http://www.ncbi.nlm.nih.gov/pubmed/23755929
Tramadol, oral: Lofwall MR, Walsh SL, Bigelow GE, Strain EC. Modest opioid withdrawal suppression efficacy of oral tramadol in humans. Psychopharmacology (Berl). 2007 Oct;194(3):381-93. http://www.ncbi.nlm.nih.gov/pubmed/1760500