Thorpe 1970.

Methods	R, DB, PC, parallel‐group study 1 episode treated with up to 2 doses of study medication. Capsules taken at onset on headache
Participants	Typical history of tension headache without other causes* n = 52 (completed to extent that reports could be analysed) No demographic data Baseline pain not reported
Interventions	Fiorinal‐Pa (aspirin + caffeine + isobutylallylbarbituric acid + paracetamol), n = 25 Placebo, n = 27
Outcomes	PI: 5‐point scale 4 h after 1st dose Response = reduction ≥ 2 grades on PI AEs
Notes	* Lance JW. Treatment of chronic tension headache. Lancet 1964;1:1236‐9 Oxford Quality Score: R2, DB1, W0
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	"According to tables set out by Smart". Judged adequate
Allocation concealment (selection bias)	Unclear risk	Not reported
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	No details reported
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	No details reported
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Reported on participants who "completed to extent that reports could be analysed". Unclear what this means. No mention of withdrawals or imputation
Size	High risk	< 50 participants per treatment arm (25‐27)