Fredheim 2006.

Methods	Case series Duration: 9 months
Participants	N = 12 enrolled Primary Condition: Low back pain Baseline pain score: Mean 5.8 (Range 3 to 9; standard measure of variance not reported) / 10 NRS Time since onset: Not reported Mean age: 60.2 years Female: 42% Previous opioid analgesia: All patients had taken strong opioids without good pain control or with unacceptable side effects, including oral slow release morphine (n = 7), oral oxycodone (n = 2), and transdermal fentanyl (n = 3). All took morphine for 2 weeks prior to methadone to enable equianalgesic dosing of morphine to methadone.
Interventions	Oral methadone Initial dose: Based upon patients' pre‐study daily morphine dose Titrated up to a mean on 202 mg/day (range 50 to 800 mg.day) Supplemental analgesia: Not reported. Patients were instructed to contact the study physicians in case of breakthrough pain.
Outcomes	Adverse events
Notes	Pain also reported but not included in analysis because outcome data were reported for fewer than 10 participants Data on discontinuation not included in analysis because patients discontinued study opioid but continued treatment on another opioid, therefore not discontinuing from the study or opioids altogether
Risk of bias
Bias	Authors' judgement	Support for judgement
Comparability of patients at baseline and follow‐up (continuous data) All outcomes	Low risk	(No continuous outcomes included in analysis)
Selection method random or consecutive	Unclear risk	Not reported
Prospective	Low risk	Prospective
Free from confounding treatment(s)	Unclear risk	Not reported
Patient compliance monitored and reported at at least 85%?	High risk	Greater attrition
Attrition and right censoring less than 15% (continuous data) All outcomes	Low risk	(No continuous outcomes included in analysis)
Funding from a source without financial conflict of interest?	Unclear risk	Not reported, but since generic drugs were prescribed seems unlikely.