Fangman 1963.

Study characteristics
Methods	Type: preclinical Design: 12‐period cross‐over design (4 repetitions of standard placebo, 2 repetitions of 2 doses of active placebo, 2 repetitions of 2 doses of experimental drug) Objective: to investigate the effects of morphine on radiant heat pain thresholds and ischaemic muscle pain thresholds Treatment duration: instant (single bolus per cross‐over period) Follow‐up duration (including treatment duration): 2 hours per cross‐over period Washout between cross‐over periods: each cross‐over treatment probably on separate days
Data	Country: USA Condition: experimental pain (radiant heat pain and ischaemic muscle pain) Number of people randomised: 4 randomised to a sequence of interventions Number of people analysed: 4
Comparisons	Active placebo: phenobarbital (2 groups: 30 mg and 60 mg) Standard placebo: water Experimental intervention: morphine (2 groups: 7.5 mg and 10 mg) Administration: IV
Outcomes	Participant‐reported outcome: radiant heat pain threshold (pricking pain) and ischaemic muscle pain threshold (both probably assessed during the 2‐hour cross‐over period) Observer‐reported outcome: none Harm outcome: qualitative summary effect and side‐effect experienced by each participant Co‐intervention outcome: none
Terminology for active placebo	"Active placebo" a priori
Scores and unpleasantness of the active placebo	Adequacy: 3 Risk of therapeutic effect: 1 Unpleasant/neutral/pleasant: unpleasant
Funding and conflicts of interest	Funding and conflicts of interest not reported
Notes	Not in meta‐analysis for any outcome
Risk of bias
Item	Authors' judgement	Support for judgement
Free from risk of bias arising from the randomisation process	Unclear	No information.
Free from risk of bias in selection of the reported result All outcomes	Unclear	No information.