Mahmoud 2021.

Study characteristics
Methods	Design: parallel Duration: 16 weeks Assessment: baseline and post‐intervention Country: Egypt
Participants	Pain condition: neck pain Population: adults with chronic neck pain Minimum pain intensity: no Inclusion criteria Chronic neck pain for > 15 days per month and lasting at least 3 months Exclusion criteria Physical and mental health comorbidities Total participants randomised: 80 Age in years (mean): 46.6 Gender: 52/80 were female Pain duration in years (mean, SD): NR
Interventions	Amitripyline 5 mg n = 40 TCA Fixed dose Amitripyline 10 mg n = 40 TCA Fixed dose
Outcomes	Pain intensity Withdrawal
Missing data methods	Completer‐only analysis
Funding source	Non‐pharmaceutical: "This work was funded in part by Fayoum University Hospitals (Fayoum, Egypt) and by the authors’ personal resources."
Conflicts of interest	The authors declare that there are no conflicts of interest regarding the publication of this paper.
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Simple randomisation using a randomisation table created by a computer software program
Allocation concealment (selection bias)	Low risk	Participants were allocated using sealed opaque envelopes.
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Double‐blind with identical study drugs
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Self‐reported outcomes from blinded participants
Incomplete outcome data (attrition bias) All outcomes	High risk	Completer analysis only Attrition Total: 10/80 (12.5%) Amitriptyline 5 mg: 5/40 (12.5%) Amitriptyline 10 mg: 5/40 (12.5%)
Selective reporting (reporting bias)	Unclear risk	Outcomes published match trial registry though retrospectively registered
Other bias	Unclear risk	Confusing reporting of primary outcome. In the text, it says that neck pain (as measured by the Neck Pain Driving Index) decreased by 71.9% ± 13.4% in the 10 mg group, which was greater than the decrease in the 5 mg group (47.3% ± 17.3%). However in the figure it says that the decreases were 48.3% for 5 mg and 68.2% for 10 mg.