Atkinson 2007.

Study characteristics
Methods	Design: parallel Duration: 12 weeks Assessment: baseline and post‐intervention Country: USA
Participants	Pain condition: low back pain Population: adults with low back pain Minimum pain intensity: NR Inclusion criteria Aged 21‐65 Low back pain (T‐6 or below) present on a daily basis for at least 6 months Exclusion criteria Comorbid physical and mental health conditions Total participants randomised: 121 Age in years (mean, SD): NR Gender: NR Pain duration in years (mean, SD): NR
Interventions	Placebo (benzotropine mesylate 0.5 mg) n = 26 Identical Active placebo ‐ anticholinergic Fixed dose of 0.5 mg Desipramine 50 mg n = 17 TCA Fixed dose Desipramine 100 mg n = 17 TCA Fixed dose Desipramine 150 mg n = 18 TCA Fixed dose Fluoxetine 20 mg n = 14 SSRI Fixed dose Fluoxetine 40 mg n = 14 SSRI Fixed dose Fluoxetine 60 mg n = 15 SSRI Fixed dose
Outcomes	No useable data provided
Missing data methods	ITT with LOCF
Funding source	Non‐pharmaceutical: US Department of Veterans Affairs
Conflicts of interest	NR
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Participants were randomised using a computerised random number generator
Allocation concealment (selection bias)	Low risk	Randomisation was completed by a research pharmacist not involved in other aspects of the study
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Double‐blinded, double‐dummy design, no significant difference in participants guessing allocation
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Self‐reported outcomes by blinded participants
Incomplete outcome data (attrition bias) All outcomes	High risk	ITT with LOCF Attrition: Total: 38/121 (31.4%) Attrition by arm NR
Selective reporting (reporting bias)	Unclear risk	Only 1 outcome prespecified in protocol. Do not perform their original analysis
Other bias	Low risk	No other sources of bias were identified.