Randomisation and masking(‘blinding’)
Participants were randomly assigned to receive racemic ketamine hydrochloride (100 mg/mL) or midazolam hydrochloride (5 mg/mL) in a 1:1 ratio. Both drugs were clear solutions for injection, prepared by a trial pharmacist, presented in vials of identical appearance. All study personnel (including the main statistician conducting analyses) were masked to the randomisation sequence, except for the trial statistician generating the sequence, the trial pharmacist and the Data Safety Monitoring Board members. Participants and raters were asked to guess their treatment allocation 3–4 days after the first treatment (pre-treatment at session 2) and after the last treatment at RCT end, and to provide reasons for their guess. See Supplementary material for further details.